Effects of ecological changes induced by various sagebrush control techniques on non-game birds
by Louis Brown Best
A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE in Fish and Wildlife Management
Montana State University
© Copyright by Louis Brown Best (1970)
Abstract:
This study, conducted in central Montana during the summers of 1968 and 1969, was designed to
determine the effects of various sagebrush control measures on non-game birds. Study plots were
established in sagebrush-grassland habitat and subjected to the following treatments: total kill spray,
strip spray, partial kill spray, defer control and open control. Plots were sprayed with 2,4-D in late
June, 1968.
The total kill spray eradicated the sagebrush (Artemisia tridentata), increased grass coverage, and
reduced the occurrence of forbs. Similar but less extreme vegetational changes followed partial kill.
Only on the total kill spray plot did Brewer's Sparrow (Spizella breweri) breeding pairs notably decline
following spraying (54 percent). No significant change occurred in Vesper Sparrow (Pooecetes
gramineus) pairs on the sprayed plots. Although both birds utilized sagebrush for nesting cover, the
Vesper Sparrow nested on the ground, while the Brewer's Sparrow nested within the shrub. Vesper
Sparrows generally utilized smaller sagebrush for nesting cover than Brewer's Sparrows. The Brewer's
Sparrow tended to select larger sagebrush for nest sites when the shrub was dead, while spraying
apparently did not influence shrub size selected by the Vesper Sparrow. Often the Brewer's Sparrow
compensated for the lack of foliage by selecting large, densely branched sagebrush. Additional
concealment by grass tended to be greater at nest sites of both species when the shrub was dead. Plant
foods (primarily grass seeds) represented a greater portion of the diet of birds collected on sprayed
areas than of those obtained from unsprayed areas. Animal foods showed an opposite trend.
Differences in major plant and animal foods occurred in amount rather than variety as a result of
spraying. The dependence upon sagebrush for nesting cover will largely determine the ultimate effects
of sagebrush control on the Brewer's and Vesper Sparrows. In presenting this thesis in partial fulfillment of the require­
ments for an advanced degree*at Montana State University, I agree that
the Library shall make it freely available for inspection.
I further
agree that permission for extensive copying of this thesis for scholarly
purposes may be granted by my major professor, or, in his absence, by
the Director of Libraries.
It is understood that any copying or publi­
cation of this thesis' for financial gain shall not be allowed without
my written permission.
Signature
o ^ i a a -
Date
iW v A
B .
2.0,19 7 0
EFFECTS OF ECOLOGICAL CHANGES INDUCED BY VARIOUS S A G E BRUSH CONTROL
T ECHNIQUES ON' NON-GAME BIRDS '
by
■ LOUIS BROWN BEST
A thesis submitted to the Gra d u a t e Faculty in partial
f u l f i l l m e n t o f the-requir ements for the degree
of
M A STER OF SCIENCE
.
in
Fish and Wildlife M anagement
Approved:
c
Head, M a j o r Department
Chairman, Examining Committee
Gradu'at/e "Dean
M O N T A N A STATE UNIVERSITY
Bozeman, Montana
June, 1970
iii
ACKNOWLEDGMENT
To the following-, among- others, I wish to express sincere appreci­
ation for their.contributions- to this study: Dr. Robert L. Eng, Montana
State University, for technical supervision and guidance in preparation
of the manuscript; Mr. Francis' G-. Feist, former graduate student at
Montana State University-, for his work,in initiating the non-game bird
investigation and for orientation to the various phases of the study;
Dr. Edward F. Schlatterer- and Mr.. Duane Pyrah, Montana Department of
Fish and Game, for assistance in the field; Dr. Don C. Quimby and Dr.
Richard J. Graham, Montana- State University, for critical reading of
the manuscript;-. Mr. Thomas W. Mussehl, Montana Department of Fish and
Game, for assistance and cooperation in various phases of the study;
the other graduate students who'worked on the project; and to my wife,
Kathleen, for patience and encouragement.
During the study, I was sup­
ported by the Montana State Department of Fish -and Game .under Federal
Aid Project N o . W-105-R-4 and No. W-105-R-5, and the United States
Department of the Interior, Bureau of Land Management.
iv
TABLE OF.CONTENTSPage
VITA .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ii
A C K N O W L E D G M E N T .. . . . .
iii
TABLE OF CONTENTS . . . . .
iv
LIST OF T A BLES . . . . . .. . . . ; _ _ _ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
v
LIST OF FIGURES .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vii
A B S T R A C T ... . . . . . . . . .
ix
INTRODUCTION . . . . .
I
DESCRIPTIO N OF STUDY A R E A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■. . . . . . . . . . . . . .
, 5
RESULTS A ND DISCU S S I O N . . . . . . . . . . . . . . . . . . . . . . .
'
-
12
;
Changes in V egetation . . . . . . . . . . . . . . . . . . . .
Breeding Bird Populations . . . . . . . . . . . . . . . . . . . . . . . . . .
Nest Site Selection .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Food Habits .. . . . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . .
12
17
32
47
CONCLUSION S . . . . . . . . . .
61
AP P E N D I X __ _ _ . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
L ITERATURE C I T E D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
73
V
LIST OF TABLES
Table
1.
2.
3.
4.
Page
COMPARISON OF VEGETATION ON THE WINNETT TOTAL'KILL SPRAY
PLOT BEFORE AND AFTER SPRAYING FOR TOTAL KILL OF SAGEBRUSH
WITH 2,4-D AS DETERMINED BY MEASUREMENTS WITHIN 20 X 50
CENTIMETER PLOTS AT BREWER'S AND VESPER SPARROW NEST SITES.... 65
COMPARISON OF VEGETATION ON THE-IVERSON PARTIAL
PLOT BEFORE AND AFTER SPRAYING FOR PARTIAL KILL
WITH 2,4-D AS DETERMINED BY MEASUREMENTS WITHIN
■ CENTIMETER PLOTS AT' BREWER'S AND VESPER SPARROW
KILL SPRAY
OF SAGEBRUSH
20 X 50
NEST SITES.....67
ESTIMATED NUMBERS OF BREEDING BIRDS ON THE-WTNNETT DEFER
CONTROL PLOT . . ;_____
,22
ESTIMATED NUMBERS OF BREEDING BIRDS ON THE WINNETT TOTAL KILL
SPRAY PLOT ■..........................................
5.
ESTIMATED NUMBERS OF BREEDING BIRDS ON THE WINNETT STRIP
SPRAY PLOT ..... .'....... ......................... ..:.......... 24
6.
ESTIMATED NUMBERS -OF BREEDING BIRDS -ON THE IVERSON OPEN
CONTROL P L O T .... V .... ............................... ......... 26
7.
ESTIMATED■NUMBERS OF BREEDING BIRDS ON THE IVERSON PARTIAL
KILL SPRAY PLOT ....... ........ ......... ........ .............. 27
8.
AVERAGE CANOPY -COVERAGES OF SAGEBRUSH IN THE VICINITY OF
VESPER SPARROW ■NESTS .......... ..... ........... . .............. 69
9.
AVERAGE CANOPY COVERAGES OF SAGEBRUSH IN THE VICINITY OF
BREWER'S SPARROW NESTS ......... ................................ 70
10.
DATA COLLECTED FROM BREWER'S AND VESPER SPARROW NEST SITES
LOCATED ON THE-WTNNETT STRIP SPRAY PLOT IN 1969 ;............. 71.
11.
DATA COLLECTED FROM BREWER'S AND VESPER SPARROW NEST SITES
LOCATED ON THE WINNETT TOTAL KILL SPRAY-PLOT IN 1968 AND
1969 ............................ .............................. .72
12.
FREQUENCY OF OCCURRENCE AND PERCENT OF TOTAL VOLUME COMPRISED
BY ITEMS FOUND IN GIZZARDS OF BREWER.'S SPARROWS COLLECTED
DURING THE SUMMER OF 1968 ON AN AREA SPRAYED WITH 2,4-D FOR
TOTAL KILL OF SAGEBRUSH .......... ■...................... .
23
vi
• LIST OF T A BLES (CONTINUED)
Table
Page
13.
FREQUENCY OF OCCURRENCE.-AND-PERCENT OF TOTAL VOLUME COMPRISED
BY ITEMS FOUND IN GIZZARDS. OF BREWER'S SPARROWS COLLECTED ON
THE KING STUDY AREA DURING JUNE AND JULY, 1969 .... ............ 52
14.
FREQUENCY OF OCCURRENCE. AND' PERCENT OF TOTAL VOLUME COMPRISED
BY ITEMS FOUND I N ■GIZZARDS OF ;VESPER SPARROWS COLLECTED DURING
THE SUMMER QF 1968 ON A M AREA.SPRAYED WITH 2,4-D.FOR TOTAL
KILL OF SAGEBRUSH ., ...... .... ............. .... ...'....... ........
I
15.
56
FREQUENCY -O F ■OCCURRENCE AND PERCENT OF TQTAL VOLUME COMPRISED
'BY ITEMS' FOUND IN GIZZARDS OF VESPER SPARROWS COLLECTED ONTHE KING STUDY AREA DtfRlNG JUNE AND JULf, 1969 ................. 58
-
.
vii
LIST OF FIGURES
.
Figure
1.
■
Map showing' the locations of the sagebrush control
study areas
...........................................
i
2.
3.
Page
"
4
I 1
Locations of: the five study plots in relation to the
various treatments .................................... .....
6
Fluctuations among' years in percent canopy coverages of
grasses, forbs, and shrubs on the Winnett •total kill spray
plot and Iverson partial kill spray plot .... ......... ..
13
4.
Winnett defer control plot
18
5.
Winnett total kill spray plot ..............................
18
6.
Winnett strip spray plot ......
19
7.
Iverson open control plot ......................
20
..............................
8. . Iverson partial kill sprayplot .............................
20
9.
28
Estimated numbers of breeding pairs of Brewer’s
Sparrows...
10.
Estimated numbers of breeding pairs of Vesper Sparrows,....
30
11.
Estimated total numbers of breeding bird pairs ............
31
12.
Typical habitat of Brewer's Sparrow nest sites ............
34
13.
Typical habitat of Vesper Sparrow nest sites ..............
34
14.
Average percent canopy.coverages of the various sagebrush
height classes at all Brewer's and Vesper Sparrow nest,
sites located on unsprayed portions of the Winnett study
area and Iverson study area ......... *...... ...............
36
Volumes.of sagebrush selected as nest sites by the Brewer's
Sparrow and Vesper Sparrow . ............ ................. .
40
16.
Vesper Sparrow nest No. 26 .................................
43
17.
Brewer's Sparrow nest No. 21 .................. ............
43
15.
viii
LIST OF FIGURES (CONTINUED)
Figure
Page
18.
Brewer's Sparrow nest No. 5 ...................... .........
45
19.
Brewey's Sparrow nest No. 18 ............ . . ................
45
20.
Percept of the total volume of gizzard contents comprised
by plant and animal foods in Brewer's Sparrows collected
on areas unsprayed and sprayed with 2,4-D for total kill
of sagebrush .....
48
Percent of the total volume of gizzard contents comprised
by plant and animal foods in Vesper Sparrows collected on
areas unsprayed and sprayed with 2,4-D for total kill of
sagebrush .................
55
21.
I
ix
ABSTRACT
This study, conducted in,central Montana during the summers of
1968 and 1969, was designed to determine the effects of various sage­
brush control measures o n .non-game birds.
Study plots were established
in sagebrush-grassland,habitat and subjected to the following treat­
ments: total kill spray, strip spray, partial kill spray, defer control
and open control. Plots.were sprayed with 2,4-D in late June, 1968.
The total kill spray eradicated the sagebrush {ATtemis'ia tr-identatd) ,
increased grass coverage, and reduced the occurrence of forbs.
Similar
but less extreme vegetational changes followed.partial kill. Only on
the total kill spray -plot did Brewer's Sparrow {Sy-izeVta bvewevi-) breed­
ing pairs notably decline following spraying (54 percent). No signifi­
cant change occurred in,Vesper Sparrow (,Pooeoetes gramineus) pairs on
the sprayed plots; Although both, birds, utilized sagebrush for nesting
cover, the Vesper Sparrow nested on the ground, while the Brewer's ■
Sparrow nested within the shrub. Vesper Sparrows generally utilized
smaller sagebrush for nesting cover than Brewer's Sparrows. The Brew­
er's Sparrow tended,to select.larger sagebrush for nest sites when the
shrub was dead, while spraying apparently did not influence shrub size
selected by the Vesper Sparrow. Often the Brewer's Sparrow compen­
sated for the lack of foliage by selecting large, densely branched
sagebrush. Additional concealment by grass tended to be greater at
nest sites of both species when the shrub was dead. Plant foods,
(primarily grass seeds) represented a greater portion of the diet ;of
birds collected on sprayed areas than of those obtained from un­
sprayed areas.. Animal •foods ,showed an opposite trend. Differences
in major plant and animal foods occurred in amount rather than variety .
as a result of spraying.
The dependence upon sagebrush for nesting
cover will largely ,determine the ultimate effects of sagebrush control
on the Brewer's and Vesper Sparrows.
INTRODUCTION
Large acreages’ of sagebrush Inr the West- have been subjected to .
various control methods to increase forage production for domestic
livestock.
Despite continued sagebrush manipulation, little is known
of the effects of such practices on wildlife habitat.
To determine the
ecological effects of various sagebrush control measures, a 10-year co­
operative study was' initiated in 1965 by the Montana,State Fish and Game
Department and the Bureau of Land Management.
One aspect..of this study was to.determine the effects of sagebrush
control through aerial spraying on non-game.bird populations.
Feist
(1968a) reported on a pre-spray investigation, conducted during the sum­
mers of 1966 and 1967.
My study was initially planned to collect post­
spray data during the summers of'1968 and 1969.
Due to a delay in spray­
ing; pre-spray data were collected during the summer of 1968.
The literature revealed limited quantitative data on the effects.of
sagebrush removal on non-game birds.
Carhart (1954) states that the.
Sage Sparrow, Brewer's Sparrow, and Sage Thrasher are among the birds
that will sufffer through eradication of large acreages of sagebrush.
The census results obtained by Scott, Scott, and Scott (1966) suggest
that sagebrush spraying tends to increase the total number of birds;
but certain species dependent on the sagebrush, such as. the Brewer's
Sparrow, tend to be eliminated with the sagebrush.
My major objectives were to determine the effects of sagebrush
manipulation on the food and cover requirements -of ^non-game species of
•
birds.
•
-
2
-
Research was concentrated in four major areas: changes in vege­
tation, breeding bird populationsi.nest site selection, and food habits
D E S C R I P T I O N 1 OF STUDY AREA
The area of study was located in Petroleum County in central Mon­
tana within 20 miles' of.Winnett (Figure I).
According to.Gieseker (1938)
the climate of Petroleum County is semiarid, being characterized by rela­
tively low rainfall and wide temperature extremes.
The mean annual pre­
cipitation is 12.57 inches and the mean annual temperature is 45.4 F.
The total precipitation and average temperature for the period March,
April and May, 1968 were.4.45 inches and 44.8 F, respectively.
same measurements for 1969 were 2.20 and 44.2.
The
For the period June,
July•and August, 1968 the total precipitation and average temperature
were .8.80 inches and 65.2 F, respectively; and for 1969, 6.69 and 65.6
(TI. S . Department of .Commerce weather station at Flatwillow 4ENE) .
Sagebrush-grassland predominates in the area.
misia tv-identata)
Junegrass ;(,Koetevta
Sandberg bluegrass
green needlegrass
row
(Avte-
was by far the most abundant shrub on the study area.
Bluestem wheatgrass .{Agvppyron
sedge
Big sagebrush
smithii),
av-Lstata) , bluegrass
(,Poa seaunda),
also common.
tain '(Plantago spp.), Hood's.phlox
American vetch
(,Bputeloua gTaottis) ,
(Boa
spp.), particularly
(Sti-pa aomata),
and
were dominant grasses. . Needleleaf
(Aoh-tllea millefolium),. fringed
pogon dubius), and
species
needle-rand-thread
(Stipd. viriduta)
(Carex eleoehar-is)'was
blue grama
Prevalent forbs included yar­
sagewbrt
(Artemisia frigida),
(Phlox hoodii), common
(Vioia amerioana).
salsify
plan­
(Trago-
—4—
NETT AR
MONTANA
NETT
N
Y E l l O V WAT ER
^RESE IV OI R
IV V i *1
I
SCALE - MILES
0
1
2
3
ERSON AREA
Figure I.
Map showing the locations of the sagebrush control study
areas.
METHODS
The five study plots (Figure 2) selected in 1966 for intensive
study each measured' 40 acres, and' were gridded throughout at 330-foot
intervals with small plastic flag markers projecting above the sage­
brush.
In 1968 three plots were aerially sprayed. Two pounds of isoctyl
ester of 2,4-D (2,4-dichiorophenoxyacetic ,acid) in 6 gallons of water
per acre was applied-on the Winnett total kill spray plot.
The same
mixture was applied in strips on the Winnett strip spray plot.
One
pound of dimethylamine salt of 2,4-D" in 6 gallons of water per acre
was applied on the Iverson partial kill spray plot.
The Winnett defer
control and Iverson open control plots received no treatment.
The
spraying, initially planned for May, was delayed until June 19-21 due
to inclement weather.
Grazing of cattle was permitted on the Iverson
1
open control plot, but the other four plots have been deferred from
grazing by domestic livestock since 1967. /Prior to 1967 the Iverson
study area was m o r e .intensively grazed than the Winnett study area.
Bird censuses were conducted on the five study plots during the
height of the nesting season, from June 14 to July 12, 1968 and from
June 4 to July 10, 1969.
Generally two plots were censused each day;
the.first census beginning approximately 5:15 a.m. and the second
approximately 7:30 a.m., the beginning time being alternated for each
plot on successive censuses.
strong-winds or rain.
Censuses were not conducted on days with
Each plot was-censused seven times in 1968 and
at least eight times in 1969.
—6—
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SBSB Bi m — ~
m %sBKi
B SSB
JK SK
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W IN N E T T s t u d y a r e a
LEGEND
2]
H H
]
g H
defer c o n t r o l
OPEN CONTROL
TOTAL KILL SPRAY
PARTIAL KILL SPRAY
I ^ j j j STRIP SPRAY
N
/
0
660
1320
SCALE-FEET
IVERSON S TU D Y AREA
Figure 2
Locations of the five study plots in relation to the various
treatments.
— 7—
The census-method employed .was similar to the territory-mapping
technique reported by.Williams (1936) and used by Feist (1968b) in the
pre-spray study.
The procedure consisted of walking along one set of
grid lines during the first half of the census.and during the second
half, walking the set perpendicular to the first.
was followed on subsequent visits.
The same pattern
Sight observations were recorded on
a grid map similar to that illustrated by Kendeigh (1944).
Birds were
recorded where first.observed on the ground to minimize bias resulting
from reaction to my presence.
A new grid map was used for each censusi
Binoculars (7 x 35) were used to aid in field identification.
Addi­
tional information recorded during a census included: location of newly
discovered nests, the number of eggs.or young in the nests, singing
males, adults carrying' food for young, juveniles, sex if discernible,
and behavioral notes.
Composite maps' for each species and for each plot were constructed
at the end of the censusing season.
A different color was used to re­
cord the observations of each census ^
To aid in interpreting the re­
sults, additional symbols were used to distinguish during which half,of
the census the birds were observed, singing males, adults carrying food,
and juveniles.
A cluster of four or more observations for a species was
arbitrarily selected as indicating the territory of a breeding pair
(Warbash 1958).
The estimated numbers.of breeding pairs were calculated
for each plot and converted to pairs per 100 acres.
-8Nests- were located by three methods.
All nests located in 1968 and
several located in 1969 were discovered by flushing the attending adult
from the nest while conducting censuses.
In 1969 a concerted effort
was made to locate as many nests as possible on the Winnett strip spray
and Winnett total kill spray plots.
To accomplish this, six men, spaced
approximately 30 feet apart, traversed each' plot several times until it
had been completely covered.
The paths traversed on the Winnett strip
spray plot were perpendicular to the strips.
I found additional nests .
by observing adults carry food to the young in the nest.
When a nest
was located, an adjacent sagebrush was marked with a colored plastic
ribbon for future location.
Vegetational' measurements were taken on the study plots at nest
sites of the Brewer's Sparrow
(Pooeoetes gramineus)',
(Spizetta bveweri)
and Vesper Sparrow
the two species most frequently encountered.
■A modification of the method employed by Daubenmire (1959) to
measure canopy coverage of vegetation was used at each nest site located
in 1968.
To compare postt-spray with pre-spray vegetation, similar data
were gathered at nest'sites' located on the Iverson partial kill and Winnett total kill spray plots.in 1969.
Twenty plot frames, each 20 x 50
centimeters, were placed at 5-foot intervals along a tape extended 25
feet from the nest site in each of the four cardinal compass directions.
The percent canopy coverage of each plant species, and percent cover of
bare ground, rock and plant litter (both standing and reclining) were
-9visually estimated "wrthiir edch plot frame.
The cover classes used were:
Class 1 = 0-1 percent-; Class 2 = .1-5 percent; Class 3 = 5-25 percent;
Class 4 = 25-50 percent'; Class'5 = 50-75 percent; Class 6 = 75-95 per­
cent; and Class 7 - 95-100 percent.
used i n •tabulating the.data.
Midpoints of the cover classes were
Frequency of occurrence within the plot
■frames w a s .also determined for each plant species.
Henry Jorgensen, a
graduate student in botany at Montana State University, assisted in plant
identification.
Canopy coverage'of' sagebrush was also measured at each nest site by
line intercept (Canfield 1941), using the same four 25-foot lines.
‘The
sagebrush intercepts were grouped into the following height classes:
Class-I =0"-6 inches; Class 2 = 6-12 inches; Class 3 = 12-18 inches;
Class 4 = 18-24 inches; Class 5 = 2 4 - 3 0 inches; and Class 6 = 30+ inches;
Additional information recorded about'each sagebrush utilized as a
nest site included: shrub height and diameter; whether the shrub was
alive, partially dead, or completely.dead; amount of concealment pro­
vided by the shrub; nest height (in the case.of the Brewer's Sparrow);
and additional cover provided by grass.
To better express the size o f .
the sagebrush, height and diameter were mathematically combined into a
single numerical;expression of volume.
Assuming the sagebrush to have
approximately an oblate spheroid shape, the volume was calculated by
the formula V .= 4/3Trh2b, where ."a" is the major semi-axis (half the
diameter) and'"b" is'the minor-semi-axis (half the height)
(Selby 1965).
-10Brewer's and- Vesper' Sp&rrows.were collected for food habits data
during June, July and- August', 1968 and June and July, 1969.
Weather
permitting, collections were made during the middle of each month.
Birds were collected in the evening (5:00 to 8:30 p.m.) in 1968, but
during the late morning and early.afternoon (9:30 a.m. to 1:45 p.m.)
in 1969.
In 1968 birds were collected 16 miles west of Winnett.on an
800-acre.area sprayed with 2,4-D for total kill of sagebrush in June,
1967 and deferred from grazing until 1969.
In 1969 birds were collec­
ted on the King study area (Figure I ) , both from an unsprayed area and
from an area (approximately 260 acres) sprayed for total kill in June,
1968,
Grazing b y livestock had been deferred on both areas since 1967.
Birds were collected with a .22 caliber rifle using bird shot or a .410
shotgun.
Caution was taken" to avoid collecting birds n e a r .the borders
between sprayed and unsprayed areas.
Gizzards were selected for analysis due .to the absence of a notice­
able crop.
The gizzards were preserved in 10 percent "'formalin for later
analysis.
The procedure for food habits analysis was identical to that used
by Feist (1968a).
The gizzard contents were segregated into piles of
like materials with the aid of a dissecting microscope.
Since the total
food volume in passerine birds is so small, measurement of individual
items is impractical (Martin, Gensch, and Brown 1946).
Therefore,
visual estimates'were made of the percentage each item constituted of
-li­
the total volume-.of gizzard contents.
The- monthly diet was tabulated by
the aggregate percentage method (Martin'
et at.
1946).
Frequency of
occurrence was also calculated.
Seeds found in the gizzards were identified by comparison with the
reference collection at the'Montana Grain Inspection Laboratory at Boze­
man.
Those I was unable to identify were sent to the Federal Seed Lab­
oratory in Sacramento, California.
Insects and insect fragments were
identified by referring to Judd (1901) and Ross (1966).
Dr. Norman L.
Anderson, Professor of Entomology at Montana State University, assisted
in identification of insects.
Scientific and vernacular names of all bird species are.as given in
the American Ornithologists-’ Union Check List of North American Birds,
fifth edition.
Plant nomenclature follows that used by Booth (1950) and
Booth and Wright (1966).
RESULTS AN D D ISCUSSION
Changes in Vegetation
Feist (1968a) presented a detailed description of the pre-spray
vegetation on each study.plot during the summers.of 1966 and 1967.
made similar vegetational measurements in 1968.
I
With the exception of
grass cover on the Winnett" total kill spray plot, the percent canopy
coverages on the five study plots.recorded by Feist were consistently
lower than those I obtained (Figure 3).
This could have resulted from
personal differences.in estimating the percent coverages within the.
plot frames.
Although the percentages differed, the relative cover
provided by grasses (and grass'-like plants), forbs, and shrubs on each
plot was very comparable, and indicated a consistency in vegetation on
each study plot during the pre-spray years.
All pre-spray data suggest
that in general there was a greater coverage of shrubs on the Iverson
Study area than on the'Winnett-study area, while the opposite was true
of forbs and grasses'.
This' may be a result of the more intensive graz­
ing practices foilnd on the .Iverson area prior to 1967.
By far the most abundant shrub species encountered was big sage­
brush.
A 100 percent kill of sagebrush was observed on the Winnett.
total kill spray plot in 1969;, as determined by line intercepts taken
at Brewer's and Vesper Sparrow nest sites and visual inspection through
out the study plot.
In 1969 the Winnett strip spray plot was character
ized by intermittent'areas of live sagebrush, total kill, and partial
kill.
The kill strips were approximately 100 feet wide while the-live
PERCENT CANOPY COVERAGE
GRASSES
GRASSES
FORBS
FORBS
SHRUBS
SHRUB
19 66 -6 7
Figure 3.
1969
19 66 -6 7
1968
Fluctuations among years in percent canopy coverages of grasses (and grass-like
plants), forbs, and shrubs on the Winnett total kill spray plot (a) and Iverson
partial kill spray plot (b). 1966-67 data obtained from Feist, 1968a.
-14strips averaged about 80' feet.
A slight wind during spraying caused
drift resulting in transitional areas between some.strips.
also some.regions of incomplete kill within the kill strips.
There.were
No not­
able change occurred in the percent dead sagebrush on the Winnett.defer
control plot from 1966 to 1969.
On the Iverson partial kill spray plot
line intercepts showed 53 percent of the sagebrush dead in.1969, while
in 1968 only 9 percent was. dead'.
A visual inspection revealed the kill
to be.quite homogeneous throughout the plot, being characterized by a
mixture of shrubs completely alive, totally dead, and partially killed.
Approximately 9 percent of the sagebrush was dead on the Iverson open
control plot in 1966, but in 1669' line intercepts revealed about 26
percent dead sagebrush..
The cause of this increase is.not known.
Changes in plant species composition following spraying were
measured at Brewer's and Vesper Sparrow nest sites on the Winnett total
kill and Iverson partial kill spray plots.
These two plots were selec­
ted for comparison since they represented two degrees of sagebrush con­
trol.
Mean canopy coverage and frequency of occurrence of each' plant
species encountered on these two plots before and after spraying are
listed in the Appendix, Tables I and 2.
Data are also presented on
plant litter, rock and bare ground.
Marked changes occurred in the percent canopy coverages provided
by.grasses, forbs, and shrubs on the Winnett total kill spray plot as
a result of spraying (Figure 3a).
The grass cover present in 1969
-15lncreased- 82 percent over that, in 1968, while the coverages provided by
forbs-and shrubs decreased 9.2 and 100 percent, respectively.
All species
,
of grass- showed an increase in coverage after spraying, with the excep­
tion of bluegrass.species*
frequency of occurrence-..
The same trends held true with respect to
The canopy coverage of bluestem wheatgrass,
green needlegrass-, and Junegrass approximately doubled, while that of
bluegrass species was reduced to nearly onerhalf.
leaf sedge.also increased several fold.
Coverage of.needle-
All major forb species de­
creased in,percent canopy coverage and frequency of occurrence from
1968 to 1969-.
The two most abundant forbs during the pre-spray period,
American vetch and HoodjS .phlox', .both were reduced to coverages of l ess.
than I percent'.
As previously mentioned", big sagebrush, the dominant
shrub, was completely eliminated.
Although vegetation'al changes on the Iverson partial kill spray
plot were not as extreme as on the Winnett total kill spray plot, they
did' show similar trends (Figure 3b'),
The grass cover in 1969 increased
7 percent over that in 1968, while forb and shrub coverages decreased
63 and 22 percent, respectively.
The canopy coverage of most grass
species remained relatively constant between years, although the c o v - .
erage of needle-and-thread-doubled and that of Junegrass increased by.
one-third from 1968 to 1969'.
about.two-thirds.
Coverage.of bluegrass species decreased
Yarrow and fringed sagewort, the most abundant forbs
in 1968, decreased b y half in canopy coverage.
The exact reduction in
-16
big sagebrush is not known,, but data from- line intercepts indicate that
it was less than the expected- 60 percent.
The increase in ground cover-by grasses on the sprayed plots prob­
ably resulted from reduction in competition with sagebrush, and to.a
lesser extent with forbs.. Deferment from grazing also contributed to.
this increase',
Competition was undoubtedly more extreme during the
spring of 1969 since dry weather prevailed (total precipitation for the
period March, April and May was 1.23 inches below normal).
Bluegrass
species were the only grasses to show a consistent decline in canopy
coverage following spraying..
Alley (1956) noted an increase in the
ground cover- b y species of biuegrass following sagebrush control.. Due
to reduced moisture and warmer temperatures, the plant phenology in
1969 was approximately I month ahead of' that in 1968.
As a result,
biuegrass species were largely desiccated and difficult to recognize
when vegetational measurements were taken, thereby causing a possible
under-estimation of their coverage.
The quantity of plant litter increased following spraying.
In
1969 the coverage of reclining plant.litter on the Winnett total kill
spray plot increased 58 percent over that in 1968, while standing litter
increased 80 percent.
Corresponding increases for the Iverson partial
kill spray plot were 22 and 54 percent, respectively.
Much of this in­
crease was due to the inclusion of dead sagebrush in the coverage pro­
vided by plant litter1.
However, deferment from grazing, resulting in
■"17*no forage utilization by livestock during the growing season, was also
undoubtedly responsible for some increase in litter.
A reduction in the percent bare.ground also occurred between years.
On the Winnett total kill spray plot measurable bare ground decreased
25 percent from 1968 to 1969^ and on the" Iverson partial kill spray plot
it decreased 17 percents
A relationship existed -between the degree of vegetational change
and the extent of sagebrush -kill.
Apparently, the vegetation on the
two control plots remained unchanged.
The Winnett strip spray plot in­
cluded conditions' characteristic of the total kill, partial kill, and
defer control plots,
Photographs of the five study plots during the
summer of 1969 are presented in Figures 4 through 8.
B r e e d ing-B ird Populations'
Census results of non=-game species of birds for each study plot
during the 1968 and 1969 breeding seasons are presented in Tables 3
through 7.
Although the censuslng period in 1968 was approximately 2 weeks
later than in 1969, this probably had little effect on the data ob­
tained since the nesting season in 1968 was also 2 weeks later.
er conditions'were mayor influents in this delay.
Weath­
The spring of 1968
(April, May and" June) was characterized by average temperatures 2.0 F
below-normal and total precipitation 3:95 inches above normal, while
Figure 4. Winnett defer control plot.
This plot was characterized by a sub­
stantial growth of all vegetative
types (grasses, forbs, and shrubs).
Figure 5. Winnett total kill spray
plot. Following spraying this plot
contained a more vigorous growth of
grasses with fewer forbs and no live
sagebrush.
Figure 6. Winnett strip spray plot.
A live strip appears to the right and
a kill strip to the left. This plot
contained habitat characteristics of
both control and sprayed plots.
Figure 7. Iverson open control plot.
Intensive and extensive grazing has
resulted in sparce grass cover on this
plot.
Figure 8. Iverson partial kill spray
plot. A partial kill of sagebrush with
minor increases in grasses and decreases
in forbs characterized this plot follow­
ing spraying.
-21for 1969 the- corresponding measurements were 1.7 F above normal and .09
inch-below normal.
The Brewer's Sparrow was the most abundant Species on all study
plots except the Winnett total kill spray in 1969.
Vesper Sparrows.were.
second in abundance-and the Western Meadowlark•(SturneZZa
third.
negteota)
All three species .established territories on all study plots
during both years.
The ■Brewer-'s Sparrowy Vesper-Sparrow^ and Western Meadowlark uti­
lized the Winnett defer control plot for breeding both in 1968 and in
1969 (Table 3).
While there was no change in the estimated breeding
pairs of-Brewer's- Sparrows from-1968 to 1969, Vesper Sparrow breeding
pairs decreased by 15 percent-.
The estimated total breeding bird pairs
on the study.plot decreased 3 percent from 1968 to 1969.
Species composition of the breeding bird populations on the Winnett
total kill spray plot was identical to that on the Winnett defer control
for both 1968 and.1969 nesting seasons (Tables 3 and 4).
Breeding pairs
of Brewer's' Sparrows 'decreased by 54 percent from 1968 to 1969, while
Vesper Sparrow pairs increased 8 percent.
Total breeding bird pairs ■
experienced a 19 percent decline.
Five species utilized the Winnett strip spray plot for breeding in
1968 (Table 5).
In addition to the three species common to all Winnett
plots , the Lark Bunting
(AsZo
fIammeus^
^CalamoBipiza' melonooorys)
also nested on the; plot.
and Short-eared Owl
In 1969 only three breeding
TABLE 3.
-ESTIMATED- NUMBERS. OF BREEDING BIRDS ON. THE WINNETT DEFER CONTROL PLOT.
Species-^
Average N o .
Obs./Census
19682
Number
Pairs
Pairs Per
■ 100 Acres
,Average No.
-Obs/ Census-
19693
Number
Pairs
Brewer's Sparrow
39
18
45
39
18
Vesper Sparrow
27
13 •
32.5
23
11
9
4
Western Meadowlark
6
3
7.5
Horned Lark
I
O4
0
Short-eared Owl
—
Unidentified Juvenile5 • I
TOTALS
74
—
. 0
34
—
—
—
I
0
85.0
•
Pairs Per
100 Acres
45
27.5
10
—
0
0
—
--
—
72
33
82.5
Species averaging less than .5 observation per census:
1968: Killdeer, Lark Bunting, and Loggerhead Shrike.
1969: None.
2- Data obtained from-seven'censuses': June 18, June 22,"June 26, July 2, July 4, July 7, and
July 10.
3 Data obtained from eight censuses': June 6% June 8, June 13, June 15, June 19, .June 23,
July I, and July 9.
4 Zero indicates the absence of- an established territory within the plot.
5-Unidentified- juveniles were either Brewer's or Vesper .Sparrow young.
TABLE 4.
ESTIMATED NUMBERS OF BREEDING BIRDS ON THE WINNETT TOTAL KILL SPRAY PLOT.
Average. No..:
-Obs.•/Census-
1968'2
Number
Pairs
Pairs Per
.100 Acres
Average No.
Obs./Census
Brewer's Sparrow
27'
13
32.5
11
6
Vesper Sparrow
29
30
24
13
32.5
5-
Species-1■
. 12
1969 3
Number
Pairs
Pairs Per
100 Acres
15
3'
I
2.5
4
2
Horned Lark
I '
O4
0
I
-0
0
I
0
o.
Lark Bunting
Unidentified Juvenile 5 •
TOTALS
-.
-.
—
'
-23-
Western Meadowlark
I
I61
0
0
26
65.0
—
41
21
•
52.5
1 Species- averaging less than'.5 observation per census:
1968:"Lark Bunting.
1969: None.
2 Data obtained from seven censuses: June 18, June 19, June 26, June 27, July 4, July.5, and
July 8.
3 Data obtained' from nine censuses': June 4, June 6, June 9, June 13, June 18, June 21, June
23, July I , and July .9..
4 Zero'.indicates the absence of: an established territory within the plot.
5i Unidentified- juveniles were' either ■Brewer ’s or Vesper Sparrow young.
TABLE 5.
ESTIMATED .NUMBERS OF BREEDING BIRDS ON THE NINNETT STRIP SPRAY PLOT.
Species1
Average-'N o .
. Obs./Census
19682
Number
Pairs'
Pairs Per
100 Acres
Average No.
Obs./Census
1969 3
Number
Pairs
■-> ■
Pairs Per
100 Acres
' 17
42.5
34
16
40
26
13
32.5
22
12
30
Western Meadowlark
3
2
5
3
Horned L ark..
I
.1
Lark Bunting'
I
Short-eared Owl
Unidentified Juvenile5
Brewer ?s Sparrow
38-
Vesper Sparrow -
TOTALS
- 5
7.5
- 2.5
—
--
—
O4
0
—
—
—
I
I
2.5
—
—
—
I
.0
.o •
—
—
—
71
34
85.0
61
31
77.5
1 Species averaging less than .5 observation per census:
1968: Mourning Dove.
1969: Lark Bunting, Mourning Dove, and' Unidentified Juvenile.
2 Data obtained from seven censuses: June 19', June 22, June 27, June 29, July 5, July 7,
■and July 12.
3 Data obtained from eight censuses-: June 4, June 8 , June 9, June 15, June'19, June 21,
July I,- and July 10. .
4- Zero indicates the absence, of- a n .established territory within the plot.
5 -Unidentified juveniles were either Brewer’s or Vesper Sparrow young.'
-25species were observed by census, although a Short-reared Owl nest was
discovered-from-which the young had departed before the censusing sea­
son-.
A comparison between years shows a 6 percent decrease in Brewer's
Sparrow, breeding pairs and an 8 percent' reduction in Vesper Sparrow
pairs'.
An 11 percent.decline was- noted for the total breeding bird
pairs.
The Iverson open control plot experienced the greatest variation
in species composition between years (Table 6).
The Brewer's Sparrow,
Vesper Sparrow, Western Meadowlark, and Horned Lark
{Evemophila abpes-
tr-Ls) utilized the plot for breeding both years, while the Short-reared
Owl nested- only in 1968 and the Lark Bunting and Sage Thrasher
sooptes monianus'')
only in 1969.
(.Oveo-
Brewer's Sparrow breeding pairs de­
creased by. 10 percent from 1968 to 1969; while Vesper Sparrow-pairs
dropped.30' percent.
No. change Occurred in total breeding bird pairs.
Three species utilized the Iverson partial kill spray plot for
breeding b o t h ,in 1968 and in 1969, while the Horned Lark established
a territory on the. plot only In 1968. (Table 7).
No change occurred in
the number of breeding piairs of- Brewer 's Sparrows between years, but
the Vesper- Sparrow pairs increased by 18 percent.
Total breeding bird
pairs increased 7 percent.
With the-exception of minor population fluctuations, only on the
Winnett total kill spray plot did the Brewer's Sparrow breeding popula­
tion experience a decided'decline from 1968 to 1969 (Figure 9).
The
TABLE 6.
ESTIMATED■NUMBERS O F BREEDING BIRDS ON THE IVERSON'OPEN CONTROL PLOT.
1968%
Species*
Average N o .
Obsv/Gensus
' Number.
Pairs.
Pairs Per
100 Acres
Average No.
Obs</Census
1969 1
3
2
Number
Pairs
■Pairs Per
100 Acres
Brewer’s Sparrow
44
20
50
41
18
Vesper Sparrow
20
10
25
14
7
17.5
Western Meadowlark
3
I
2.5
5
2
5
Horned Lark
I
. I
2.5
2
I
2.5
Lark Bunting
I
O4
0
5
4
Short-eared Owl
I-
I
2.5
--
Sage Thrasher"
Unidentified Juvenile 5
TOTALS
•
—
—
±
0
7T
33
-I.
0
——
82.5
68
—
. 45
10
——
I
2.5
33
82.5
1 Species' averaging less than *5 observation per census:
1968': Upland Plover.
1969': Unidentified Juvenile.
2 Data obtained from seven censuses': June 21, June 23, June 28, July I, July 3, July 6,
and July 11,
3 Data obtained from eight censuses-: June 5, June 7-, June 11, June 14, June 17, June•20,
June 24', and July. 2.,
4Zero indicates the absence, of.an established territory within the plot.
5-Unidentified juveniles were either Brewer’s or Vesper Sparrow young.
TABLE 7. - ESTIMATED NUMBERS OF BREEDING BIRDS ON THE IVERSON PARTIAL KILL SPRAY PLOT, '
Average No.
Obs,/Census
19682 '
Number
■Pair's
Pairs Per
100 Acres
Brewer’s ■Sparrow
34
16
40
31
16
40
Vesper Sparrow
21
11
27.5
26
13
32.5
2.5
'5
2
2.5 .
—
—
62
31
Species1
"
Western Meadowlark
I
I
Horned Lark
I
I
Unidentified Juvenile5
I
.-O4
0
58
29
72.5
TOTALS
,
19693
.Average No. Number
■Obs./Census■ Pairs
Pairs Per
100 Acres
5
.
—
77.5
z1 Species averaging less than .5 observation per census:
1968: Common Nighthawk, Lark Bunting, Long-billed Curlew, and Short-eared Owl.
1969: Black-billed Magpie, Eastern Kingbird, Horned Lark, Lark Bunting, Marsh .Hawk,
Short-eared Owl, and Unidentified Juvenile.
2 Data obtained from seven censuses: June 14, June 21, June 23, July I, July 3, July 6,
and July 9.
3 Data.obtained from eight censuses: June 5; June-7, June 11, June 14, June 17j June 20,
June 24, and July 2.
^ Zero indicates the absence of an established territory within the plot.'
5 Unidentified juveniles were either Brewer’s or Vesper Sparrow young.'
■
—28—
WINNETT
DEFER
CONTROL
Figure 9.
WINNETT
WINNETT
IVERSON
TOTAL
OPEN
STRIP
KILL
SPRAY
CONTROL
SPRAY
STUDY PLOTS
IVERSON
PARTIAL
KILL
SPRAY
Estimated numbers of breeding pairs of Brewer's Sparrows
-29Vesper Sparrow showed slightly greater variations in breeding pair num­
bers on the five study plots, the most noticeable being the reduction
on the Iverson open control plot (Figure 10).
Breeding pairs of the
Western Meadowlark increased in number on all five study plots in 1969.
A decrease in Horned Lark pairs occurred on at least two study plots.
Baumgarten (1968) states that the Lark Bunting shows no strong attach­
ment for any particular nesting grounds, and may fluctuate greatly in
abundance in a given area from one year to the next.
This explains
the sudden appearance of four breeding pairs of Lark Buntings on the
Iverson open control plot in 1969.
The total breeding bird pairs exhibited a general constancy in
numbers between years for each study plot (Figure 11).
The greatest
variations occurred on the Winnett total kill spray followed by the
Winnett strip spray plot, where the breeding pairs declined by 19 and
11 percent on the two plots, respectively.
A close correlation was noted between estimated numbers of breed­
ing pairs and average numbers observed per census.
The ratios of
breeding pairs to numbers observed ranged from 1:1.8 to 1:2.3 for the
Brewer's Sparrow and from 1:1.8 to 1:2.4 for the Vesper Sparrow.
The pre-spray breeding bird population data obtained by Feist
(1968b) were not included in the present discussion for several rea­
sons.
Due to differences in interpreting census data, I consistently
estimated greater numbers of breeding pairs in relation to the aver-
-30-
20
1968
18
| 1969
16
2 14
<
12
Q
LU
< 10
%
v, 8
6
4
2
0
WINNETT
DEFER
CONTROL
Figure 10.
IVERSON
WINNETT
WINNETT
OPEN
STRIP
TOTAL
SPRAY
CONTROL
KILL
SPRAY
STUDY PLOTS
IVERSON
PARTIAL
KILL
SPRAY
Estimated numbers of breeding pairs of Vesper Sparrows
CO
QC
<
Q-
Q
LU
I—
<
CO
LU
WINNETT
DEFER
CONTROL
Figure 11.
WINNETT
IVERSON
WINNETT
OPEN
STRIP
TOTAL
SPRAY
CONTROL
KILL
SPRAY
S T U D Y PLOT S
IVERSON
PARTIAL
KILL
SPRAY
Estimated total numbers of breeding bird pairs
-32age numbers observed'per census than those estimated by Feist.
Cen­
suses were conducted almost.entirely in July oh the Winnett study area
in 1966.
Most-of the Brewer's and Vesper Sparrow young had departed
from the heht by the- first week in July in 1968 and 1969.
July census
results would therefore be largely confined to late nesters and/or renesters, and would not be comparable to censuses conducted during the
height of the breeding season.
Flood conditions prevailed throughout
the Iverson study area in June., 1967.
According to Feist (1968b) this
severely interrupted nesting activities.
Since variations due to the
above causes could not'be attributed to natural fluctuations.in breed­
ing bird populations and since I was able to collect pre-spray data
(without the above,limitations), only 1968 and 1969 census results are
presented.
Nest Site Selection
West site selection data were obtained from 40 nests of the Brew­
er's Sparrow and. 24 Vesper Sparrow nests located on the five study
plots.
Feist (1968a) presented a listing of plant species encountered at
Brewer's and Vesper Sparrow nest sites during the pre-spray summers of
1966 and 1967.
I collected similar data during the summer of 1968.
From these data it appears that the coverage and variety of grass and
forb species present in the vicinity of Brewer's Sparrow nests dif-
-33- .
fared.little from that near Vesper Sparrow nests.
However, a no­
ticeable difference was evident in the coverage of sagebrush.
Since
sagebrush appeared to be the influential factor in nest site selection,
detailed data are presented for this shrub.
Sagebrush in the vicinity of Brewer's and Vesper Sparrow nest
sites differed both in density and size.
In general, the Brewer's Spar
I
row selected regions of more dense and larger sagebrush:for nest sites
(Figure 12), while the Vesper Sparrow showed a preference for more,
sparse and smaller sagebrush (Figure 13).
Measurements, of live and
dead sagebrush were combined, since.the dead brush was proportionately
distributed among the various.height classes present.
The average
canopy coverage of sagebrush, as determined by line intercept, was
27.9 percent (range 16.4 to 59.8) in the vicinity of Brewer's Sparrow
nests and 18.0 percent (range 12;7 to 25.3) near Vesper Sparrow nests
located on urisprayed portions of the Winnett study area.
On the un­
sprayed portions of the Iverson study area the corresponding, cover­
ages for the Brewer's and Vesper Sparrows were 34.6 (range 29.0 to
46.0) and 33.5 percent (range 31.4 to 37.8), respectively.
The
greater sagebrush coverage at nest sites on the Iverson study area re­
flects. the. effects.of more intensive grazing by livestock, and may be
responsible for the small difference in canopy coverages at nest sites
of the two bird species.
The distribution of sagebrush height classes in the vicinity of
Figure 12. Typical habitat of Brewer's
Sparrow nest sites. This species pre­
fers to nest in areas where sagebrush
is taller than average and of
considerable density.
Figure 13. Typical habitat of Vesper
Sparrow nest sites. Normally the Ves­
per Sparrow nests in areas where sage­
brush is smaller than average and
sometimes of sparse coverage.
-35nest sites differed more than total sagebrush ,cover.
Figure 14 shows
the percent canopy coverages of various heights of sagebrush at Brew­
er's and Vesper Sparrow nest sites on unsprayed portions,of the Winnett
and Iverson study areas.
In selecting-a nest site the.Brewer's Sparrow
utilized areas ,with greater coverage of taller sagebrush than did the
Vesper Sparrow.
An attempt was made,to determine if the above density and size
preferences persisted in the nest site selection following spraying.
The average canopy coverages of sagebrush (both total coverage and
coverage.by height.class) in the vicinity of Vesper Sparrow and Brew­
er's Sparrow nests located on the five study plots,are presented in
the Appendix in Tables 8 and 9 j respectively.
The small number of
nests, permits only limited analysis.
Fluctuations.between years of total sagebrush canopy coverage a t ,
Vesper Sparrow nest sites showed no apparent relationship to the spray­
ing of plots.. Sites on all plots, except the Winnett total kill spray,
experienced increased sagebrush density. , Inconsistencies between years
also appeared in the ,coverage by various height classes at nest,sites.
In 1969 the usage.of taller sagebrush increased on,three plots, de­
creased on tbe Winnett total kill spray, and showed no definite
change on the Iverson open control.
Changes from 1968 to 1969 i n .sagebrush coverage near Brewer's
Sparrow nests did.show a possible trend.
Total canopy coverage at nest
18
U
,14
^
BREWER’S SPARROW
■
VESPER SPARROW
uj
O
<
O
<
£ 12
>
14
£ 12
>
O
u 10
O
u IO
>
>Q-
CL
§
<
O
8
Z 8
<
U
u
I—
z
LU
LU
U
U
Z 6
06
LU
CL
SS
4
CL
0-6
6-12
12-18
18-24
HEIGHT CLASSES IN INCHES
(a)
Figure 14.
0-6
6-12
12-18
18-24 24-30
HEIGHT CLASSES IN INCHES
(b)
Average percent canopy coverages of the various sagebrush height classes at
all Brewer's and Vesper Sparrow nest sites located on unsprayed portions of
the Winnett study area (a) and Iverson study area (b).
(Values were ob­
tained from line intercept data and represent the percent coverage of the
total intercept by each height class.)
-37sites increased on all plots, except for the Iverson open control,,
which experienced a very slight decline.
Nest sites on the Iverson
open control plot had a reduced coverage of taller sagebrush in 1969,
while those on the Iverson partial kill spray exhibited a slight in­
crease.
The Winnett total kill and strip spray plots showed an in­
creased representation of taller, sagebrush at the nest sites, while
no definite change in height class usage could be determined for the
Winnett defer control plot..
The presence of kill and.live strips, as well as partially killed
areas, on the Winnett strip spray plot in .1969 offered the Brewer’s
and Vesper Sparrows alternatives in selecting nesting habitat.
Data
collected from nest sites located on this plot in 1969 are presented
in the Appendix, Table 10.
Neither species of bird showed a definite
preference for the conditions present in any one area.
Of the ten
Brewer’s Sparrow nests located on t^e plot, four were inside live
strips (although at times only by a few feet), three were inside kill
strips,and three were in partially killed regions.
The five Vesper
Sparrow nests were located as follows: three were inside live strips,
one was on a boundary between strips, and one was located in’a partially
killed region.
Fluctuations in total canopy coverage of sagebrush at nest sites
on the Winnett strip spray plot in 1969 bore no relationship with nest
placement relative to the stripsi
The greatest sagebrush coverage in
-38taller height .classes occurred at Brewer's Sparrow nest sites within
the kill strips, followed by those within live strips and partially
killed regions.
in, a kill region.
No Vesper Sparrow nests were located completely with­
Nest sites within live,strips and partially killed
regions were similar in coverage by various.heights of sagebrush.
The specific shrub selected as nest cover ^was also investigated
to aid in determining preferences and effects of sagebrush manipula­
tion on these preferences.
Although both birds utilized sagebrush
for nesting cover, the Vesper Sparrow nest was placed on the ground
beneath the sagebrush, while that of the Brewer's Sparrow was located
within the shrub.
Feist (1968a) made similar observations.
Brewer's
Sparrow nests averaged 6.5 inches (range 3.5 to 9.5) above the ground,
measuring from the top of the nest.
Placing the nest above the ground
limits the minimum sagebrush height that the Brewer's Sparrow can use
for nest location and still have sufficient cover above the nest.
Nests of the Vesper Sparrow were generally located under smaller
sagebrush than those in which Brewer's Sparrow nests were found.
Feist (1968a) noted a similar trend during the pre-spray summers of
1966 and.1967;
The average height of the sagebrush in which Brewer's Sparrow
nests were placed was 16.0 inches (range ll.O to 24.5) when the sage­
brush was alive, 15.5 inches (range 12.0 to 19.0) when partially dead,
and 20.0 inches (range 16.0 to 25.0) when completely dead.
For the
-39Vesper Sparrow the average ,height-of .sagebrush under which nests .were .
located was 9.5 inches (range 5.5 to 13.5) when alive, 11.5 inches
(range 11.0 to 12.0) when partially dead, and 10.5 inches (range 6.5
to 13,5) when completely dead.
Volume of the sagebrush plant is a more accurate indicator of
size than height.
Volumes and condition (live, partially dead, or
completely dead) of all sagebrush in which nests of the Brewer's Spar­
row or Vesper Sparrow were located are presented in Figure 15. . Sage­
brush selected by.the Brewer's Sparrow as nest,sites had an average
volume of 2.72 cubic feet when the shrub was alive, 3.13 cubic feet
when partially dead, and 6.49 cubic feet when completely.dead.
The
corresponding figures for tl>e Vesper Sparrow were 1.06 cubic feet
for live sagebrush, 1.10 cubic feet for partially dead, and *84
cubic feet for completely dead.
Nest sites located on the Winnett total kill and strip spray plots
were compared to determine if a change in size preference of sagebrush
within a plot occurred as a result of spraying.
In 1968 the Brewer's
Sparrow selected live sagebrush on the Winnett -total kill spray plot
averaging 2.87 cubic ,feet in volume.in which to place the nest, while
tbe dead sagebrush in 1969 utilized for nest sites averaged 6.02 cubic
feet.
Vesper Sparrows nested under,live sagebrush averaging .51 cubic
feet in volume, while the dead shrub's selected as nest cover averaged,
.53 cubic feet.
On the Winnett strip spray plot sagebrush selected
V O L U ME IN CUBIC FEET
V O L U M E IN CUBIC FEET
1 2 3 4 5 6 7 8 9
NUMBER OF NESTS
I
0
1
1 2 3 4 5 6 7 8 9
NUMBER OF NESTS
10
(a)
Figure 15.
Volumes of sagebrush selected
Vesper Sparrow (b).
nest sites by the Brewer's Sparrow (a) and
-41for nest-sites by the Brewer's Sparrow averaged 2.84 cubic feet when
the shrub was alive, 3.72 cubic feet when partially dead, and 7.43
cubic feet when completely ,dead.
No Vesper Sparrow nests were found
under partially dead shrubs, but the live shrubs selected for nest
sites averaged 1.48 cubic feet and those.that were.dead 1.42 cubic
feet.
When the sagebrush was killed through sprayirtg, the Brewer's Spar­
row showed a tendency to select larger shrubs for,nest sites.
The vol­
umes of sagebrush utilized as nest sites were somewhat comparable when
the shrub was alive or only partially dead.
However, the average vol­
ume of dead shrubs selected for nest.sites more than doubled that.oflive shrubs.
The size of sagebrush selected by the Vesper Sparrow for nest .cover
appeared to be little influenced by spraying.
Volumes of sagebrush
utilized for nest sites varied little regardless.of whether the,sage­
brush was alive, partially dead, or completely dead.
This may indicate
a greater versatility in nest site selection on the p a r t :of the Vesper
Sparrow.
Feist (1968a) also concluded ,that the Vesper Sparrow had
less specific nesting requirements with regard to sagebrush than the
Brewer's Sparrow.
A qualitative evaluation ,was made of the amount of cover provided
by the shrub, and any additional concealment furnished by grass.
These
data, as well as other pertinent information on nest site selection of
—42—
the Brewer's and Vesper Sparrows, are presented in Tables 10 and 11,in
the Appendix for nests, located on the Winnett strip spray and Winnett
total kill spray plots, respectively.
Nest sites on these two plots,
were selected since comparisons could be made between the relative
nest concealment on unsprayed and sprayed areas.
On the average, dead sagebrush furnished less concealment for
Vesper Sparrow nests than live shrubs, although the sample of nests
was small providing inconclusive data.
The additional concealment
provided by grass tended to be greater when Vesper Sparrow nests were
located beneath dead sagebrush than when found under live shrubs.
Vesper Sparrow nest No. 26 illustrates the grass cover often found
under dead shrubs (Figure 16).
Additional grass cover at nest sites
may have resulted from a selective preference on the part of the bird
and/or from the general increased grass coverage in areas sprayed to
kill sagebrush.
The dead or partially dead sagebrush selected by the Brewer's
Sparrow as nest sites often provided better nest.concealment than did
live shrubs.
This superior concealment resulted from the bird's se­
lection of larger, more,heavily branched shrubs which compensated for
loss of foliage.
Brewer's Sparrow nest No. 21 exemplified this se­
lectivity for a large and densely branched dead sagebrush (Figure 17).
The foliage on live sagebrush utilized as.nest sites was generally
quite dense and capable of providing excellent concealment, but was
Figure 16. Vesper Sparrow nest No. 26.
The nest under this dead sagebrush re­
ceived considerable concealment by grass
in addition to that provided by the
shrub.
Figure 17. Brewer's Sparrow nest No. 21.
Large, heavily branched sagebrush char­
acterized by dense, rank growth were often
selected as nest sites on areas sprayed
for total kill.
-44often intermittent due to less profuse branching.. Brewer's Sparrow
nest No. 5 illustrates the cover that live sagebrush is capable of
providing (Figure 18)..
As was noted with the Vesper Sparrow,., grass provided additional
cover, at several Brewer!s Sparrow nest sites (Appendix, Tables 10 and
11).
Grass cover was,negligible at all five nests.located in live
sagebrush;
A relationship was observed between the concealment ,pro­
vided at nest sites by dead or partially dead sagebrush and that sup­
plied by grass.
Either some ...or negligible grass cover was present
at the five shrubs which ,by themselves provided,excellent concealment.
Some grass cover was present at the two sagebrush plants supplying
good concealment.
The two.dead sagebrush furnishing only fair con­
cealment were surrounded by a considerable coverage.of grass.
Thus,
at nest sites.located in dead sagebrush the.lack of brush cover was,
at least partially, compensated for by an increased amount of grass;
Brewer's Sparrow nest No. 18 best illustrates this compensating effect.
(Figure 19).
The nest was located in a smaller than average, sparsely-
branched sagebrush which provided only fair concealment, while the
grass completely surrounded .the nest and supplied considerable cover. .
The total concealment provided was very good;
No nests of the Brewer's
Sparrow were found in dead sagebrush where both the sagebrush and grass
coverages ,were only.fair or less.
Concealment undoubtedly plays a significant part in the nest site
Figure 18. Brewer's Sparrow nest No. 5.
This live sagebrush with its moderately
dense patches of foliage provided good
nest cover.
Figure 19. Brewer's Sparrow nest No. 18.
This slender, sparcely-branched sagebrush
provided little concealment for the nest.
Were it not for the abundant grass cover
present, the nest would be openly exposed.
-46selection of the Brewer's Sparrow and to a lesser degree .in that of the
Vesper'Sparrow.
In the case of.the Brewer's Sparrow lack of foliage
was often compensated for by selection of large sagebrush which were
rank and heavily branched.
The preference for rank growth may be re­
sponsible for the tendency of the Brewer's Sparrow to select larger
shrubs when the sagebrush w a s .dead.
A heavily branched condition is
m o r e .commonly encountered in larger sagebrush.
The dead sagebrush s e - .
Iected by the Vesper Sparrow generally provided no greater cover than
the live.
Concealment provided by,grass was greater at nest sites when the
sagebrush was dead.
Although a loss of sagebrush foliage accompanies
spraying, the growth response of grass compensates, at least in part,
for the loss of cover.
Among the grass species frequently associated
with sagebrush plants were:, bluestem wheatgrass, bluebunch wheatgrass
(Agropyron spigatwn), green
needlegrass, and Junegrass.
A final point of consideration in nest site selection is the re­
action of the birds to.the sagebrush, wheather alive or.dead, regard­
less of the size or cover provided,
Brewer's Sparrow nests were found
in five live, three partially dead, and two completely dead sagebrush
on the Winnett strip spray plot in 1969.
Three Vesper Sparrow nests
were located under live sagebrush and two under dead.
Whether the
sagebrush is living or not probably is not an influential factor i n ,
nest site selection of the Vesper-Sparrow and of only minor importance.
-47If any, in that of the Brewer's Sparrow.
Available cover apparently
determines whether the bird selects;a live or dead shrub.
A high degree of inter-specific tolerance was observed for the
Brewer's and Vesper Sparrows.
feet of each other.
At times nests were found within a few
The closest proximity of nests was 9 feet apart.
No Western Meadowlark nests were found during the course of the
study.
According to Bent (1958) this species commonly nests among
grass.
It would appear that increased grass coverage following spray­
ing of sagebrush and deferment from grazing would improve the quality
and quantity of nest site cover utilized by this species.
One Sage Thrasher nest was found within a large, live sagebrush
plant (17.5 inches in height) and one Lark Bunting nest was located be­
neath a partially dead, small shrub (10.0 inches in height).
Both nests
were located on the Iverson open control plot in 1969 and in both cases
the sagebrush provided good concealment.
It is possible that elimina­
tion of sagebrush through spraying may adversely affect the nesting
habitat of these two bird species.
Food,Habits
The percent of total volume of gizzard contents comprised by plant
and animal foods,found in Brewer's Sparrows during the summers of 1966
and 1967, as recorded by Feist (1968a), are shown in Figure 20.
data represent the pre-spray diet.
These
The bulk of the animal foods during
—48—
JUNE
=100
90
80
70
60
50
40
30
20
10
0
1 9 6 7 (8)
(9)
1 9 6 8 (s)
LI
1 9 6 9 (8)
JULY
$100
= 90
O
1969
80
70
60
50
40
30
20
10
0
=100
90
UNSPRAYED
80
60
PLANT
FOODS
50
30
■ I
( # ) SAMPLE
SIZE
20
10
0
Figure 20.
SPRAYED
ANIMAL
FOODS
70
40
AUGUST
1 9 6 6 (4)
t
1967
(7)
1 9 6 8 (6)
Percent of the total volume of gizzard contents comprised
by plant and animal foods in Brewer's Sparrows collected
on areas unsprayed and sprayed with 2,4-D for total kill
of sagebrush.
1966 and 1967 data obtained from Feist
(1968a).
-49
both summers consisted of grasshoppers (Acrididae), leaf beetles (Ghrysomelidae), and snout beetles (Curculionidae).
Predominant plant.foods
included seeds of .Sandberg bluegrass, green needlegrass, and blue grama
No plant food was taken during the month of June.
Forb seeds were of.
minor importance. . A definite shift from animal.foods to plant foods
occprred as the summer progressed;
The 1968 summer diet of Brewer's Sparrows collected on an area
sprayed with 2,4-D in 1967 for total kill, of sagebrush is presented in
Table 12.
By August the birds were no longer, restricted to nesting
territories, and appeared to move at will in small groups.
Thus, the
August diet may not be entirely representative of the total kill area, .,
although the birds were collected there.
Plant.foods assumed.increas­
ing relative importance in the diet as the summer progressed. .
The pre-spray (1966-67) diets of Brewer's Sparrows.had consistent­
ly, greater proportions of animal foods and lesser proportions of plant
foods during all summer months, than the post-spray (1968) diet (Figure
20)..
In 1966 plant and animal foods comprised 22 and 49 percent, re­
spectively, of the total gizzard contents for the entire summer; while
in 1967 the values were 14 and 62 percent, respectively.
Fifty-nine
percent plant foods,and 19 percent animal foods were found in gizzards
collected during the summer of 1968.
During June and July, 1969 Brewer's Sparrows were collected ,on
defer control and total kill portions of the King study area.
This
TABLE 12.
FREQUENCY OF OCCURRENCE AND PERCENT OF TOTAL VOLUME COMPRISED BY ITEMS FOUND IN
GIZZARDS OF BREWER'S SPARROWS COLLECTED DURING THE SUMMER OF 1968 ON AN AREA
SPRAYED WITH 2;4-D FOR TOTAL KILL OF SAGEBRUSH.
GIZZARD CONTENTS
JUNE (5)1
Frequency of Percent
Occurrence of Total
Volume
(Percent)
ANIMAL FOODS:
Coleoptera (Chrysomelidae and Curculionidae)
Orthoptera (Acrididae)
Homoptera (Aphida e .and
Cicadellidae)
Insect Eggs
Hemiptera (Miridae)
Hymenoptera (Sphecidae)
TOTAL ANIMAL FOODS •
JULY (5)
Frequency o f • Percent
Occurrence of Total
Volume
(Percent)
AUGUST (6)
Frequency of Percent
Occurrence of Total
(Percent)
Volume
7
67
tr2
6
—
17
33
tr
8
6
tr
-—
—
100 ■
19
83
47
—r
—
—
—
—
—
100
40
--_
—
44 •
16
—
—
——
—
—
100
67
67
33.
33
17
17
34
21
9
3
tr
I
tr
100
47
100
60
100
68
100
80
17
4
100
20.
16
5
100
—
24
—r
80
19
80
40
40
3
tr
60
——
20
—
—
10
—
—
60
20
100
32
100
—
— .
™ .
—
— .
——
8
PLANT FOODS:
Poa secunda
Stipa Gomata
Sphenopholis spp.
Parietavia pennsylvanica
Labiatae
Chenopoditm alhvm
Phaoetia Hneaxis
TOTAL PLANT FOODS
GRIT
UNIDENTIFIED
1 Sample size.
2 Trace■(values'less than I percent).
—
-51allowed a comparison of diets on sprayed a n d .unsprayed areas, while
eliminating differences among .years in available food.caused by ,vari­
able weather conditions (principally precipitation).
Also, the dif^
ferences in availability of food items in widely separated localities
was essentially eliminated since the two areas of collection were a p - ,
proximately I mile apart.
These two sources of variation were present
in the 1966-67'versus 1968 comparisons.
Frequency of occurrence and percent of total volume comprised by,
items found in.gizzards of Brewer's Sparrows collected on the ,King
study area are presented in Table 13.
During both months greater quantities of plant bugs (Miridae) were
present in total kill diets than defer control diets, while the oppo­
site was true of beetle species and spiders (Arachnida).
Grasshoppers
were equally represented in the June diet on both areas, but were
notably more important in the July diet on the defer control area.
(Grasshoppers, probably, constituted a larger portion of the diet than
the percentages indicate, since generally only the hardest body parts
were found.)
Lepidoptera larva were.more important in the June diet
on the total kill area.
Ants (Formicidae) were equally represented
in the diets on both areas during the two summer months.
Similar in­
sect food items were found in gizzards collected from both areas dur-r
ing June, but July collections revealed four insect orders (Diptera,
Homoptera., Thysanoptera, and Odonata) present in the defer control
TABLE 13.
FREQUENCY OF OCCURRENCE A N D P ERCENT OF TOTAL VOL U M E COMPRISED BY ITEMS FOUND IN GIZZARDS O F BREWER'S SPARROWS COLLECTED ON THE KING
STUDY AR E A DURING JUNE A N D JULY, 1969.
JUNE________________________
GIZZARD CONTENTS
D E F E R C ONTROL (9) 1
Percent
Frequency
of Total
of: Occurrence
(Percent)
Volume
TOTAL KI L L (8 K
Percent
Frequency
of Total
of Occurrence
Volume
(Percent)
_________________________ JULY
DE F E R CONTROL(8)
Frequency
Percent
of Occurrence
of Total
(Percent)
Volume
TOTAL KILL (7)
Frequency
Percent
of Occurence
of Total
(Percent)
Volume
ANIMAL FOODS:
Coleoptera (Carabidae,
Ch r y s o m e l i d a e , C u r c u l ionidae,
and Staphylinidae)
Orth o p t e r a (Acrididae)
Hyme noptera (Formicidae)
Hemiptera (Miridae and Tingidae)
Arachnida
Lepi doptera Larva
Insect Eggs
Dipt e r a (Tipulidae)
Homoptera (Cicadellidae and
Membracidae)
Thysanoptera
Odonata (Zygoptera)
TOTAL ANIMAL FOODS
PLANT FOODS:
Poa seounda
Stipa eomata
Chenopodiwn albwn
Stipa viridula
Muhlenbergia spp.
Lepidium densiflorum
Sphenopholis spp.
TOTAL PLANT FOODS
GRIT
UNIDENTIFIED
100
57
75
12
88
27
86
56
22
56
33
22
33
11
I
6
5
7
4
I
tr
I
6
17
2
8
2
5
—
—
63
13
100
50
—
13
25
25
8
I
20
3
—
tr
I
2
14
14
100
29
—
75
38
75
38
38
50
13
—
—
—
—
—
13
13
6
3
100
71
100
38
4
71
57
12
15
i
—
—
7
4
29
—
—
—
IOO
—
81
33
22
—
—
—
—
—
IOO
53
7
88
26
50
I
—
—
—
—
—
—
—
—
I
13
—
13
38
25
13
—
7
tr3
I
29
I
—
14
tr
—
—
—
—
—
—
—
——
—
—
—
—
—
—
—
—
—
—
29
3
8
88
27
75
17
100
32
78
11
—
100
25
14
6
100
25
10
2
100
—
44
1 Sample size.
2 Sprayed in 1968 with isoctyl ester of 2,4-D.
3 Trace (values less than I p e r c e n t ) .
I
—
—
—
2
—
—
30
—
-53diet but not in the total kill.
During both months animal foods rep­
resented larger portions,of the diet on the defer control area than
on the total kill area (Figure 20).
Sandberg bluegrass seeds were taken in larger quantities on the
total kill area than on the defer control area during each.month.
These seeds were .probably in lower than normal amounts in the diets
on both areas since the plants were largely desiccated prior to the
summer months due to reduced moisture.
Thq most notable difference
in plant foods consumed between the two areas occurred in July.
Needle-and-thread seeds constituted a major plant food.on the total
kill area during this, month, but were entirely lacking in the diet on
the defer control area.
defer control diet.
Green needlegrass was more important in the
Forb seeds, although in small amounts, were
found entirely in the defer control diet during July.
Plant foods
were more important,in the diet of birds collected on the total kill
area than the defer control area during b o t h 1summer months (Figure 20).
Plant and animal foods,comprised 29 and 46 percent, respectively,
of the total gizzard contents for the 2 months combined on the .total
kill area.
The corresponding percentages on the defer control area
were 12 and 76 percent, respectively.
Plant foods.increased and.
animal-foods decreased in the diet on both,areas from June to July.
The portion of .the Vesper Sparrow gizzard contents comprised by plant and animal foods, recorded by.Feist (1968a) during the pre-spray
-54summers .of 1966 and 1967 are presented in Figure 21.'
Predominant ani­
mal foods during bofcti .summers included grasshoppers, snout beetles and
leaf ,beetles. ■ Seeds of green needlegrass constituted the principle
plant food.,
A
wide variety of other grass and forb seeds were .taken
in small quantities.
Animal foods ,were most important in June diets,
decreasing in July, but increasing again ,.during August.
Lowest
quantities of plant foods were encountered in June diets, but increased
during July and August.
The diet of Vesper Sparrows collected during the summer of 1968 on
an area sprayed the previous yehr for total kill is presented in Table ■
14.
By August birds were no longer confined to.nesting territoriesj
but were still quite .restrictive in their movements.
Thus, the August
diet should be indicative of that found on a total kill area.
Animal
foods decreased in the diet as summer progressed, while plant foods
were lowest in June and increased to nearly equal representation in
July and August diets.
A comparison of the pre-spray (1966-67) and post-spray (1968)
diets shows that the Vesper Sparrow consumed more plant foods,and
fewer animal foods on the area sprayed to kill sagebrush (Figure 21).
Plant foods comprised.23 percent and,animal foods 60 percent of the
total gizzard contents during the summer of 1966, and in 1967 the cor­
responding values were 37 and 44 percent, respectively.
Gizzard con­
tents for the summer of 1968 consisted of 59 percent plant foods and
ENT OF TOTAL VOLUME
PERCENT OF TOTAL VO LUME
PERCENT OF TOTAL VOLUME
-55-
2
O-
100
UNSPRAYED
90
JUNE
SPRAYED
80
70
60
50
40
30
20
10
0
1 9 6 7 (8)
100
UNSPRAYED
90
JULY
SPRAYED
80
70
60
50
40 30 •
20
10
-
0-
100
90
1 9 6 6 (12)
1 9 6 7 (U)
UNSPRAYED
80
1 9 6 9 (9)
AUGUST
1 9 6 8 (8)
1 9 6 9 (io)
SPRAYED
SSS ANIMAL
Ga FOODS
70
60
■ PLANT
■FOODS
50
40
30 ■
( # ) SAMPLE
SIZE
20
IOh
Figure 21.
0
1 9 6 6 (s)
1 9 6 7 (9)
1 9 6 8 (8)
Percent of the total volume of gizzard contents comprised
by plant and animal foods in Vesper Sparrows collected on
areas unsprayed and sprayed with 2,4-D for total kill of
sagebrush.
1966 and 1967 data obtained from Feist (1968a).
TABLE 14.
FREQUENCY OF OCCURRENCE AND PERCENT OF TOTAL VOLUME COMPRISED BY ITEMS FOUND IN
GIZZARDS OF VESPER SPARROWS COLLECTED DURING THE SUMMER OF 1968 ON AN AREA
SPRAYED WITH 2,4-D FOR TOTAL KILL OF SAGEBRUSH.
GIZZARD CONTENTS
. JULY (8 )
AUGUST (8 )
Frequency of Percent. Frequency of Percent
Occurrence of Total
Occurrence of Total
Volume
(Percent)
(Percent)
Volume.
JUNE (8)1
Frequency of Percent
Occurrence of Total
Volume
(Percent)
ANIMAL FOODS:
Cqleoptera (Carabidae,
100
Chrysomelidae, CurcuIionidae 5 and Elateridae)
Orthoptera (Acrididae)
38
25
Hymenqptera (Formicidae)
13
Homoptera (Cicadellidae)
13
Insect Eggs
—
Arachnida
—
Hemiptera (Miridae)
—
Unidentified Larva
TOTAL ANIMAL FOODS
PLANT FOODS:
Poa seounda
Chenopodium album
Limm vigidwn
Stipa oomata
Stipa viridula
Eleooha^is spp.
Polygonum lapaihifoliim
Sphenopholis spp.
Portulaceae
Carex spp.
TOTAL PLANT FOOD
GRIT
UNIDENTIFIED
100
75
25
13 .
—
—
—
—
—
—
88
88
63
1 Sample Size.
2 Trace (values less than I p e r c e n t ) .
43
100
5
75
—
—
—
13.
—
2
tr
tr
—
—
—
18
100
I
-T
—
25
25
—
---25
13
--
I
-—
50
100
20
100
36
100
. 35
100
2
tr
—
—
—
--,
—
-38
7
5
^
13
—
75
38
—
—
—
-.
—
2
——
25 ■
7
-—7
—
—
100
25
25
13
13
13.
13
100
—
——
—
69
100
100
10
100
25
I
—
12
-
tr1
2
4
—
—
—
I
tr
17
37
—
—
26
4
tr
I
I
I
tr
70
13
—
—57—
29 percent animal foods,
Vesper Sparrows were also collected .from sprayed and unsprayed seg­
ments o f the King study area during June.and July, 1969.
The frequency •
of occurrence and percent of total volume comprised by items .found in
gizzards are recorded in.Table 15.
Beetles, spiders, and Lepidoptera larvae comprised greater propor­
tions of the diet on the defer control area than on the total kill area
during both months.
Grasshoppers were present in larger,quantities in
total kill diets during June, while in July they were more ,important in
defer control diets.
Members of Hemiptera and Hymenoptera were some­
what comparable in the diefs on the two areas during June and July.
The variety of animal foods found in gizzards collected from the two
areas was very similar.
Only one order (Diptera) was represented in
defer control diets, but not in total kill.
During both months animal
foods comprised a.greater portion of the diet on the defer control
area than on the total kill (Figure 21).
As explained for the Brewer's Sparrow, Sandberg bluegrass seeds .
were less available than during years of hear normal precipitation.
The three predominant grass species (green needlegrass i Sandberg bluegrass, and needle-and-thread) were present in greater quantities dur-r
ing both,months in.total kill diets as,compared with those on the defer
control area (Figure 21).
The total gizzard,contents for tfye 2 months, on the total kill area
TABLE 15.
FREQUENCY OF OCCURRENCE AND PERCENT OF TOTAL VOLUME COMPRISED BY ITQlS FOUND IN GIZZARDS OF VESPER SPARROWS COLLECTED ON THE KING
STUDY AREA DURING JUNE AND JULY, 1969.
DEFER CONTROL(8X
GIZZARD CONTENTS
JUNE________________________
TOTAL KILL(9)^
Frequency
of Occurrence
(Percent)
Percent
of Total
Volume
________________________ JULY
DEFER CONTROL(9)
Frequency
of Occurrence
(Percent)
TOTAL KILL (10)
Frequency
of Occurrence
(Percent)
Percent
of Total
Volume
Percent
of Total
Volume
Frequency
of Occurrence
(Percent)
Percent
of Total
Volume
100
66
100
54
100
36
90
12
38
50
I
4
78
44
6
2
100
78
14
4
50
50
9
9
75
3
67
I
100
6
90
7
38
25
13
8
7
I
11
tr 3
—
—
—
—
22
22
I
10
10
tr
tr
—
—
—
—
—
11
tr
33
tr
—
ANIMAL FOODS:
Coleoptera (Bruchidae,
C a r a b i d a e , Chr y s o m e l i d a e ,
Coccinellidae and Curc u l ionidae)
Orthoptera (Acrididae)
Hymenoptera (A n d renidae and
Formicidae)
Hemip t e r a (Lygaeidae, M i r i d a e ,
and Tingidae)
Arachnida
Lepidoptera Larva
Hemip t e r a Egg
Homoptera (Cicadellidae and
Psyllidae)
Diptera (Culicidae)
TOTAL ANIMAL FOODS
PLANT FOODS:
—
—
22
6
90
100
63
100
70
100
37
67
56
15
3
7
22
44
78
11
I
I
21
tr
2
4
46
tr
—
—
—
—
—
—
40
40
90
10
10
—
—
—
—
11
11
tr
tr
—
—
—
—
—
10
10
10
—
tr
tr
tr
13
25
25
25
tr
—
—
—
—
—
—
Labiatae
—
—
Lepidium deneiflorum
Polypogon aoioulare
Sphenopholie spp.
—
—
—
—
—
—
TOTAL PLANT FOODS
i
i
i
44
I
22
11
11
11
2
tr
tr
—
—
—
—
—
—
i
63
3
100
28
100
23
100
53
63
38
5
78
33
5
4
100
—
7
90
10
9
I
1 Sample size.
2 Sprayed in 1968 with isoctyl ester of 2,4-D.
3 Trace (values less than I percent).
2
—
I
Ln
00
1
100
Poa Becunda
Stipa oomata
Stipa viridula
Chenopodiion album
C y p e m e spp.
Mtjilenbepgia spp.
Trifolium spp.
GRIT
UNIDENTIFIED
3
-59consisted of 41 percent plant foods,and 50 percent animal foods, while
on the defer control area the percentages were 14 and 80 percent, re­
spectively..
Plant foods increased and animal foods decreased in the
diet on both areas.from June ,to July.
A comparison between the food.habits of the Brewer's Sparrow and
Vesper Sparrow revealed similarities, as well as differences.
Animal foods for the two bird species were very similar.
Snout
beetles, leaf beetles, and grasshoppers were the predominant .'animal
foods utilized. . In 1969, Hemiptera, particularly plant bugs, became
a major food item in the Brewer's Sparrow diet. . The,Vesper Sparrow
fed on a greater variety.of plant foods,than did the Brewer's Sparrow,
but those utilized by the Brewer's Sparrow were also generally found in
the Vesper Sparrow diet.
All plant material was taken as seeds.
Gras­
ses, .primarily Sandberg bluegrassj green needlegrass, and needle-andthread, comprised the bulk of the plant foods for both bird species, .
supplemented with minor, amounts of forbs. . On both sprayed and,un­
sprayed areas the variety of plant foods in the Brewer's and Vesper
Sparrow diets increased during the latter part of the.summer.
In both the Brewer's and Vesper Sparrows, plant foods ,invariably
represented a greater portion,of the diet of birds collected on sprayed
areas than of those obtained from unsprayed areas, regardless of the
month or year collected (Figures ,20 and 21).
opposite trend.
Animal foods,showed an,
The dominant foods utilized by,each bird species were
—60—
the same on .sprayed a n d ■unsprayed areas.
Differences in major plant
a n d .animal foods occurred in amount rather than variety as a result of
spraying. . The 1969 data revealed a greater variety of minor animal
foods,in the gizzards of Brewer's and Vesper Sparrows collected on un­
sprayed regions,
No notable differences occurred in the numbers of
minor plant species consumed by Brewer's Sparrows on sprayed and un­
sprayed areas.
The greater variety of plant foods utilized by the
Vesper Sparrow occurred on the total kill area.
Weather also affects the available food supply.
The abundant rain­
fall in 1968, particularly during June, provided conditions favoring
plant growth, although some delay in plant phenology may have occurred.
In 1969 an abnormally dry spring resulted in early desiccation of plants
and many grass seeds failed to develop.
Greater dependence on animal
foods occurs during dry years sipce fewer plant seeds are available.
•
CONCLUSIONS
Sagebrush reduction resulted in different responses,by the two ma­
jor, bird species.
A limited kill of sagebrush (strip spray and partial
kill spray), reducing the live sagebrush by approximately ,50 percent,
resulted in.no notable change in breeding pairs of Brewer's or Vesper.
Sparrows,
Apparently neither the nesting habitat nor available food
were sufficiently reduced to cause a population decline.. A total-kill
of sagebrush resulted in a significant reduction in nestng pairs of the
Brewerjs Sparrow, but not of the Vesper Sparrow.
This decline in,the
Brewer's Sparrow may be due to: (I) a reduction in suitable nesting
cover and/or (2 ) a reduction in the,diversity of the floral habitat
with a possible limiting effect on the insqct fauna.
The Vesper Sparrow, appears to have less rigid concealment require­
ments for its nest than the Brewer's Sparrow.
The nest is placed on the
ground, sometimes,under sagebrush providing little cover.
Following
sagebrush removal, the growth response of grass would probably provide
adequate cover to protect the nest.
Such supplementary concealment fur­
nished by grass.has been noted on the spray plots. , The persistence o f ;
grass cover will depend,largely upon the intensity of future livestock,
grazing practices.
All evidence indicates that available cover is a paramount factor
in the nest site selection of the Brewer's Sparrow.
Nests of this
species were placed above,the ground in the sagebrush plant,—
the shrub
p r o v iding not only, the nest. c o v e r b u t its structural support,
Paine
■
(1968) in his presentation of the life history of the Brewer's
—62— .
Sparrow found only one report of a n e s t •a ctually tin-the g r o u n d . . F o l l o w ­
ing spraying,
the Brewer's Spar r o w c o m pensated for the la c k of protective
foliage b y selecting larger, m o r e h e a v i l y b r a n c h e d shrubs.
The du r a ­
tion of this c o mpensatory cover w i l l d e p e n d upon two factors:
rate of deterioration of the dead s a g e b r u s h plants,
and
(I) the
(2) the r apidity
and extent of sagebrush r e i n v a s i o n . . I n c r eased grass cover also p a r t i a l ­
ly c o mpensated for the loss in concealment.
If this species inherently
must nest above the ground and if no significant r e i n v a s i o n occurs b e ­
fore the commencement of sagebrush deterioration,
then conceivably the
loss of structural support a n d 1cover for the nest w o u l d m a k e ■the habitat
unsuit a b l e for nesting.
Dead s a g e b r u s h so o n lose their smaller b r a n c h e s ,
leaving only a brief upright ske l e t o n of the plant.
The timing and ex­
tent of sagebrush d e t erioratio n and r e i n v a s i o n then b e c o m e s critical.
Such sagebrush deteri o r a t i o n w o u l d p r o b a b l y not a f f e c t .the Vesper
Sparrow n e sting h a b i t a t adversely.
Although the Brewer's Sparrow utilized only sagebrush as nest cover
in this study. Hardy (1945) and Wing (1949) have observed Brewer's Spar­
rows nesting in other shrub species.
The effects of.2,4-D spray on
these species will determine their future availability.
Sagebrush treatment with 2,4-D also affects the available food
supply, for b o t h .the Brewer's and Vesper Sparrows.
Spraying eradicates
the sagebrush,.increases the coverage by grass species, and reduces the
occurrence of fo r b ,species.
Since grass seeds constitute the predomi-
-63nan t plant food, sagebrush control measures increase the available
plant food supply.
However, spraying sagebrush also reduces the diver­
sity of the flora.
This may adversely affect the insect fauna, causing
a reduction in their numbers and/or species composition.
Plant,seeds
increased in,abundance throughout the summer,and appeared to be taken
as soon as they became available.
The shift from animal to plant
foods as. the summer progresses and the consumption of-greater quanti-.
ties of plant foods,on sprayed areas may result from availability,
from a preference, or both.
If such a preference.for plant ..foods were
existent, spraying sagebrush would actually improve summer.feeding con­
ditions for the Brewer's and Vesper Sparrows.
According to Martin, Zim,
and Nelson (1951) the Vesper -Sparrow consumes more plant food during
the summer months than the Brewer's Sparrow (44 percent versus 16 per-­
cent) .
Thus, sagebrush control measures wpuld supposedly be more
i
beneficial to the Vesper Sparrow.'
The duration of changes in.food,habits due to sagebrush spraying
will depend upon the return of forb species, reinvasion of sagebrush,
and future grazing practices.
APPENDIX
-65TABLE I.
Taxa
COMPARISON,OF VEGETATION ON THE WINNETT TOTAL KILL SPRAY PLOT
BEFORE AND AFTER SPRAYING FOR TOTAL KILL OF SAGEBRUSH WITH
2,4-D AS DETERMINED BY MEASUREMENTS WITHIN 20 X.50 CENTIMETER
PLOTS AT BREWER'S AND VESPER SPARROW NEST SITES.
BEFORE SPRAYING 1
Mean
Frequency
Canopy ■
of
Coverage 3
Occurrence 4
GRASSES AND
G RASS-LIKE PLANTS
39
Agropyron smithii
24
Bqutelpua gracilis
Capex eleoeharis
I
Calamogrostis
montanensis
Distiehlis striata..
Koeleria.eristata
3
Poa s p p .
5
Sehedonnardus
paniaulatus
Stipa viridula
10
FORBS
25
Aehilleq millefolium
Allium textile
tr
Antennaria rosea.
tr
Arenaria hookeri
Artemisia frigida
Aster eaneseens
tr
Astragalus bisuleatus
tr
Astragalus gilviflorus tr.
Astragalus
tr
missouriensis
Atriplex dioiea
2
Bahia oppositifolia
tr
Cirsium undulatum
tr
Collomia tinetoria
tr
Crepis oeeidentalis
tr
Draba braehyearpa
Erigeron pumiIus
Gaura eoeeinea
I
Grindelia squarrosa.
I
Gutierrezia sqrothrae ■ I
Hymenoxys richardsonii tr
Iva axillaristr
AFTER SPRAYING2______
Mean
Frequency
Canopy
of
Coverage
Occurrence
71
50
I
5
' I
100
100
— w.
I
35
75
—
8
4
. 55
54
100
99
-- -
16
——
3
tr
63
99
23
—
tr.
tr
I
9
36
7
6
69
51
I
I
2
I
±
5
I
tr
tr
I
3
6
tr
I
.
5
4
I
10
6
4
—
—
16
14
15
8
I
——
—
3
tr
tr
tr
tr
— —
2
I
I
—
—
tr
tr
tr
3
2
I
—66TABLE I.
Taxa
(CONTINUED)..
BEFORE SPRAYING.
Mean
Frequency
Canopy
of
Coverage
Occurrence
LappuIa eekinata
-.
tr
Lepi-di-wn densiflorum
tr
Lesquerella alpLnd
—
Llmm rigidum
Lomatlim spp.
3.
I
Mlaroserls nutans'
Opuntla polyaantha
tr
tr
Orobanahe faslaulata
2
Penstemon nltldus
' 7
Phlox hoodll
tr
Plantago' spp.
I
Psoralqa argophylla
tr
Psoralea tenulflora
tr
Rorlppq Islqndlqa
tr
Sphaeralaea aoaalnea
tr
Taraxaaum officinale
Thelasperma marginatum I
I
Tragopogon■dublus
10
Viola amerloana
tr
Viola nuttqllll
21
SHRUBS
21 .
Artemisia trldentata
OTHERS
Reclining Plant Litter
Standing Plant Litter
Rock'
Bare Ground
38
39
tr
36
AFTER SPRAYING
Mean
Frequency
Canopy
of
Coverage
Occurrence
-3
tr
—
6
—
tr
I
—
tr
—
—
tr
tr
—
tr
tr
—
-.
40
4
3
8.
41
68
I
5 ■
5
3
19
3
I
—
—
I
11
—
4
—
—
21
I
—
3
I
—
18
63
I
tr
tr
—
tr
—
-.
5
—
.70
70
tr
tr
I
I
60
70
100
100
10
100
100
10
100
.
I
6
2
79
27
100
1 D a t a obtained f r o m four Dau b e n m f r e transects.
2 Data obtained from seven Da u b e n m i r e transects;
3 Percent of area covered by foliage. ,Tr. indicates v a l u e s less than
I.percent.
4 Percent occurrence among plots.
•
TABLE 2.
Taxa
'— 67“
COMPARISON OF VEGETATION ON.THE IVERSON PARTIAL
PLOT BEFORE-AND AFTER SPRAYING,FOR PARTIAL KILL
WITH 2,4-D AS DETERMINED.BY MEASUREMENTS WITHIN
CENTIMETER PLOTS AT BREWER'S AND VESPER SPARROW
BEFORE •SPRAYING1
F r e quency
Mean
. of
. Canopy
Coverage3
O c c u r r e n c e 1h
GRASSES AND
GRASS-LIKE PLANTS
Agropyron smith-ii •
Bouteloua graoil-is
Bromus gaponlpus
Bromus teotorum
Carex eleooharis
Festuoq ootoflora
Koeleria oristata
Poa spp.
Sohedonnardus
panioulatus
Stipa oomata
Stipq viridula
FORBS .
Adhillea millefolium
Androsaoe
septentriondlis
Antennaria rosea
Artemisia frigida
Astragalus spp.
Camelina micrqoarpa
Cirsium arvense
Cirsium undulatum
CoIlomia.tinotoria
Drdba b'raohyoarpa
Gqura.ooooinea.
GrindeIia squarrosa
Gutierrezia sarothrae
Hedeoma hispida
Lepidium densiflorum
Linum rigidum
Opuntia polyoantha
Phlox hoodii
Plantago s p p .
KILL SPRAY
OF SAGEBRUSH
20 X 50
NEST SITES.
AFTER SPRAYING2
Mean.
Frequency
of
Canopy
O ccurrence
Coverage
46
99
49
100
21
5
98
16
7
2
43
3
20
5
96
tr
tr
8
tr
tr
6
tr
■8
10
68
87
21
I
3
4.
8.
2
tr
tr
2
. tr
tr
tr
tr
.
tr
tr
tr.
tr
tr
tr.
tr
tr
I,
I
3
51
—
-.
11
3
73
66
14
tr
88
6
4
3
23
3
tr
2
I
—
—
■4
23
23
I
33
I
I
I.
I
3
3
3
13
2
4 ■
18
63
30
I
, 45
15
63
8
5
--
—
• I
——
—
—
—
tr.
tr
9
—
-.
—
—
I
3
—
--
—
—
8
tr
—
—
—
—
—
—
tr
I
tr
5
30
13
-68TABLE. 2.
(CONTINUED).
BEFORE SPRAYING
Mean
Frequency
of
Canopy.
Coverage
Occurrence
Taxa
Ratibida coVumnifeva
Sphaevaloea.ooo'oinea ■
■Tavaxaoun offioinale
Tvagopogori dubius
Vioia ,amevioana.
SHRUBS
Avtemisia tpidentata
tr
tr
I
I
I
36
36
I
3
12
8
,
AFTER SPRAYING
Mean
Frequency
Canopy
of
Coverage
Occurrence'
——
tr
tr
—
-.
—
3
3
I .
14 .
tr
78
28
28
71
71
,67
60
I
25
100
100
78
OTHERS
Reclining Plant Litter
Standing Plant Litter
Rock
Bare Ground
55
39
I•
30
100
99
48
98
81
100
1 D a t a obtained from six Daube n m i r e .transects.
2 D a t a o b t a i n e d ■f r o m four Daub e n m i r e transects.
3 P e rcent of area covered by.foliage.
T r . indicates v a l u e s less than
I percent.
4 Percent occurrence among plots.
I
TABLE 8.
AVERAGE CANOPY COVERAGES1 OF SAGEBRUSH IN THE VICINITY OF VESPER SPARROW NESTS.
Study Plot
Winnett Defer Control
Total Canopy, CANOPY. COVERAGES.OF VARIOUS HEIGHT•CLAS SES
(Percent)
Coverage
0-6
in.
6-12
in.
12-18 in. 18-24 in.
Year
(Percent)
-5.0
1968 (I) 2
12.7
7.7
—
1.2
17.8
3.0
1969 (I)
22.0
Winnett. Total Kill Spray 1968 (2 )
1969 (3)
Winnett Strip Spray3
Iverson Open Control
Iverson Partial Kill
Spray
6.1
12.6
13:8
6.3
5.6
2.7
1.9
1968 (3)
1969 (5)
18.1
21.9
6.0
11.6
12.6
.5
4.1
1968 (2 )
1969 (I)
31.8
34.8
2.5
10.6
L
1.1
18:4
15.3
.3
16.3
2.1
?
1968 (3)
1969 (2 )
34.4
43.6
10.6
20.5
19.2
3.1
13.0
4.5
22.2
5.0
6.9
■ .8
—
— —
.2 ;
.2
1 .Data obtained from line intercept. Coverages of live and dead shrubs.(or portions of
shrubs) are combined. .
2 Sample size.
Often
3 In 1969 this plot contained areas of live sagebrush, total kill, and partial kill,
the line intercept crossed more' than one area for a given nest site.
TABLE 9.
AVERAGE CANOPY COVERAGES 1 OF SAGEBRUSH IN THE VICINITY OF BREWER'S SPARROW NESTS.
Tc)tal Canopy . CANOPY COVERAGES OF VARIOUS HEIGHT CLASSES
(Percent)
Coverage
6- 1 2 /in.
12-18 in. 18-24 in . 24-30 in,
(Percent) 0--6 in.
Study Plot
Year
Winnett Defer Control
1968 (2)2
1969 (6 )
26.0
33.6
1.4
3.3
10.4
13.0
Winnett .Total Kill Spray 1968 (2 )
1969 (4)
20.9
25.1
5.1
9.0
9.6
11.4
Winnett Strip Spray 3
1968 (2 )
1969 (10 )
19,8
27.4
4.0
2.1
13.1
' 9.9
2.7
9.9
1968 (4)
1969 (4)
34.9
34.4
1.8
10.6
13,3
15.8
14.0
6.1
4.3
1968 (2 )
1969 (2 )
34.5 .
39.6
4.2
5.9
'18.7
18,8
10.4
1.2
2.1
Iverson Open Control
Iverson Partial Kill
Spray
1 Data obtained from line intercept.-
2.6
10.5
14.4.
6.8
12.8
3.7
2.9
—
1
— —
1.5
—
—
— —
4.3
1.2
2.3
—
'6 k
.5
f
— —
——
Coverages.of live and dead shrubs (or portions of
shrubs) are combined.
2 Sample size.
3 In 1969 this plot contained areas of live sagebrush, total kill, and partial kill. Often
the line intercept crossed more than one area for a given nest site.
TABLE 10.
Nest
No.
I
DATA COLLECTED FROM BREWER'S AND VESPER SPARROW NEST SITES LOCATED ON THE ’/INNETT SIRIP SPRAY PLOT IN 1969.
Species
Brewer's
Height
(in.)
Characteristics of Sagebrush Selected as Nest Sites__________
Sagebrush in Vicinity
Additional
of Nest Sites-3
Concealment
Percent
Concealment
Provided By
Canopy
Percent
Diameter Volume1
Grass
Coverage
Provided
Live
Condition23
Location of Nest Sites Relative to Strips
(cu. ft.)
(in.)
13.5
11
.50
Live
Fair
Negligible
23.1
73.6
Approximately 4 feet inside live strip
1.94
Live
Good
Negligible
23.2
34.1
Partially killed region of kill strip.
2.64
Live
Good
Negligible
32.6
80.4
Approximately 3 feet inside live strip.
22.7
83.7
Approximately 20 feet inside live strip.
37.6
83.0
Approximately 10 feet inside live strip.
2
Brewer's
14.5
21
3
Brewer's
18.0
22
4
Brewer1s
14.0
26
2.87
Live
Good
Negligible
5
Brewer's
24.5
30
6.68
Live
Good
Negligible
6
Brewer1s
17.0
15
1.16
Partially Dead
Excellent
Negligible
34.9
39.5
Approximately 10 feet inside kill strip.
7
Brewer's
14.0
33
4.62
Partially Dead
Excellent
Negligible
20.4
31.4
Partially killed region of kill strip.
8
Brewer1s
14.5
35
5.38
Partially Dead
Good
Some
16.0
63.8
Transitional region between strips.
Dead
Fair
Considerable
26.7
1.1
Central portion of kill strip.
Good
Some
36.4
3.0
Approximately 20 feet inside kill strip.
9
Brewer's
25.0
28
5.94
10
Brewer's
24.0
35
8.91
Dead
11
Vesper
5.5
9
.14
Live
Poor
Negligible
22.6
74.8
Central portion of live strip.
12
Vesper
11.0
12
.48
Live
Good
Negligible
30.6
85.6
Central portion of live strip.
13
Vesper
13.0
17
1.14
Live
Excellent
Some
20.2
83.2
Approximately 25 feet inside live strip.
14
Vesper
13.5
15
.92
Dead
Fair
Considerable
24.7
49.0
Boundary between strips.
15
Vesper
11.0
24
1.92
Dead
Fair
Considerable
10.S
24.1
Partially killed region of kill strip.
1 Volume calculated assuming sagebrush to have an oblate spheroid shape.
2 Live = 0-25 percent dead, partially dead = 25-95 percent dead, and dead = 95-100 percent dead.
3 Data from line intercept along 25-foot lines extended from the nest site in the four cardinal compass directions.
TABLE 11.
DATA COLLECTED FROM BREWER'S AND VESPER SPARROW NEST SITES LOCATED ON THE WINNETT
TOTAL KILL SPRAY PLOT IN 1968 AND 1969.
Nest
N o . Species
16
17
18
19
20
21
22
23
24
25
26
Brewer's
Brewer's
Brewer.'s
Brewer's
Brewer •'s
Brewer's
Vesper
Vesper
Vesper
Vesper
Vesper
CHARACTERISTICS OF SAGEBRUSH SELECTED AS NEST SITES________ Percent Canopy
Additional
Coverage o f .
Concealment Sagebrush In
Concealment Provided
Height Diameter Volume 1
Vicinity of
Condition
2
Provided
By Grass 3 . Nest Sites4
(cu.ft.)
(in.)
(in.)
12.0
15.0
22.0
16.0
18.0
19.0
8,5
7.5
6.5
23
28
18
32
34
43
13
16
10.0
8
12
11.5
17
2.23
3.51
2.16
4.97
6.31
10.65
.44
.58
.13 .44
1.01
Live
Live
Dead
Dead
D ead.
Dead
■Fair
Good
Fair
Excellent
Excellent
Excellent
Live
Live
Dead
Dead
Dead
Good
Fair
Poor
Fair
Good
Considerable
Negligible
Some
Some -
25.0
16.8
36.5
28.1
16.8
19.1
Some
Considerable
Considerable
25.3
19.1
15.4
9.9
16.1
1 Volume calculated assuming sagebrush to have an oblate spheroid shape.
2 Live sagebrush present in 1968, but only dead sagebrush available in 1969.
3 Concealment provided by grass was estimated only in-1969.
^ Data obtained from line intercept.
' LITERATURE CITED
Alley, H. P. 1956. Chemical;control of big sagebrush and its effect
upon production and utilization of native grass species. Weeds.
4(2):164-173.
Baumgarten, H . .E. 1968; Lark bunting.
In Aus till, 0. L.,' Jr., Life
histories of North American cardinals, grosbeaks; buntings, tow-,
hees, finches, sparrows, and allies. . U. S. Nat. Museum Bull. No.
237•(part 2). Smithsonian Institution Press, Wash., D. C.
1889 p p .
Bent, A. C. 1958. Life histories of North American blackbirds, ori­
oles, tanagers, and allies. U. S. Nat. Museum Bull. No. 211.
Smithsonian Institution, Wash., D. C. 549 pp.
Booth, W. E. 1950. Flora of Montana,,Part I, Conifers and Monocots.
Research Foundation at Mpntapa State College, Bozeman, Montana.
232 p p .
_____ and. J.- C. Wright.
1966. Flora of Montana, Part. II, Dicoty­
ledons. Montana Stiate■College, Bozeman, Montana,
280 pp.
Canfield, R. H. 1941. Application of the line interception method in
sampling range,vegetation.. J. Forestry.
39(4):388-394.
Carhart, A. H.
200-204.
1954.
Sagebrush is. going!
Audubon Mag.
56(5):
Daubenmire, R.
analysis;
1959. A canopy-coverage method of vegetational
Northwest .Sci. 33:43-64.
Feist, F. G. 1968a. . Breeding bird populations in relation to pro­
posed sagebrush control in central Montana. M; S. Thesis,
Montana State University.
41 pp.
_____ . 1968b. Breeding-bird populations on sagebrush-grassland
habitat in central Montana.- Audubon Field Notes.
22(6):
691-695.
Gieseker, L. F; 1938.
Soils of Petroleum County.
Expt. Stb. Bull. No, 363. 47 pp.
Montana Agr.
Hardy, R. 1945. Breeding birds of the pigmy conifers.in the book
cliff region of eastern Utah. Auk.
62(4):523-542.
-74Judd, S. D. 1901. The relation of sparrows to agriculture.
Dept. Agr., Div. Biol. Survey Bull. No. 15. 98 pp.
Kendeigh, S. C. 1944.
14(1):67-106.
Measurement of bird populations.
U. S . .
Ecol. Monogr.
Martin, A. C., R. H. Gensch, and C. P . Brown.
1946. Alternative
methods in upland gamebird food analysis. J. Wildl. Mgmt. 10(1):
8- 1 2 .
_____ ,.H. S. Zim, and A. L. Nelson.
1951. American wildlife and
plants. McGraw-Hill Book Co., Inc.,. New York, New York.
500 pp.
Paine, R. T. 1968. . Brewer's sparrow.
In Austin, 0< L., Jr., Life
histories of North American cardinals, grosbeaks, buntings, towhees, finches, sparrows, and allies. U. S . Nat. Museum Bull. No.
237 (part 2). Smithsonian Institution Press, Wash., D. C. 1889 pp.
Rosp, H. H. 1966. A textbook of entomology.
Third ed.
and Sons, Inc., New York, New York.
539 pp.
John Wiley
Selby, S . M. (editor).
1965. Standard mathematical tables.
ed. The Chemical Rubber Co., Cleveland, Ohio. 632 pp.
Scott, 0. K.., H. H. Scott,, and G.. C. Scott.
20(6):657-8.
U. S. Department of Commerce.
71(3-8):45-187,
____ 1969.
1968.
Fourteenth
1966.. Audubon Field Notes.
Climatological data Montana.
Climatological data Montana;
72(3-8):4l-183.
Warbach, ,0. 1958. Bird populations in relation to changes in land
use. J. Wildl. ,Mgmt.' 22(1):23-28.
Williams> A. B. 1936.
climax community.
Wing, L. 1949.
(I):38-41,
The composition and dynamics of a beech-maple
EcoI. Monogr. 6(3):317-408.
Breeding birds of virgin palouse prairie.
Auk.
66
_____....T11CoeTTY LIBRARIES
3 1762 10012909 5
5378
BkSk
Best, Louis Brown
cop. 2
Effects of ecologies.
changes induced byvarious sagebrush con­
trol techniques...
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