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Pinyon-Juniper Woodlands as Sources of
Avian Diversity
Kathleen M. Paulin
Jeffrey J. Cook
Sarah R. Dewey
Abstract - Results of breeding bird point counts in mature pinyonjuniper woodlands are described and compared to data from seven
other forest habitats common in northeastern Utah. Pinyon-juniper bird communities ranked second in the percentage of obligate
and semi-obligate species, third in total number of individuals
counted, and fourth in species richness and diversity. Bird species
assemblages in pinyon-juniper were similar to those found in
ponderosa pine forests but had relatively little in common with
other forest habitats in the study area. The low degree of similarity
to other forest habitats and high percentage of obligate and semiobligate species suggest that pinyon-juniper habitat contributes
substantially to landscape-level avian diversity. These results are
consistent with those of several other studies that found mature
pinyon-juniper woodlands to be an important source of nongame
wildlife habitat.
Land managers often consider mature stands of pinyonjuniper to be undesirable, or at least less desirable, than
earlier seral stages of this type, due to their lack of understory vegetation. Removal of trees through chaining or
burning is often prescribed to produce more forage for big
game and livestock, increase vegetative diversity, reduce
erosion by stimulating growth of plants with high value for
watershed protection, or prevent expansion of pinyon-juniper into adjacent grassland or shrub habitats.
Decisions about which stands to treat, and how much
acreage to treat, have most often been made on the basis of
logistical constraints such as the presence of road access or
sufficiently high fuel loads to carry a fire. Habitat values of
the mature woodlands themselves receive little consideration, in part because they appear so extensive that there
seems to be no possibility of exhausting the supply and in
part because their arid nature and lack of vegetative diversity seem inconsistent with highly productive wildlife habitat. However, a number of studies have shown that pinyonjuniper woodlands support a wide array of nongame wildlife
(Finch and Ruggiero 1993), and in some cases considerably
greater numbers of species and individuals than the more
open habitats created through treatment (for example, Sieg
1991; Sedgwick and Ryder 1987).
The growing emphasis on ecosystem management requires that we design vegetative treatments within the
context of a larger planning landscape. With this in mind,
land managers must consider where to maintain mature
pinyon-juniper stands for the values they provide, and
where to treat to meet other objectives (Goodrich, these
proceedings). This paper is intended to help managers make
such decisions by describing the contribution pinyon-juniper habitats make to avian diversity in northeastern Utah
landscapes.
Study Area _ _ _ _ _ _ _ __
The study was conducted in large stands of Utah juniper
(Juniperus osteosperma) and Colorado pinyon pine (Pinus
edulis) located within the Flaming Gorge National Recreation Area (NRA) in northeastern Utah. Sample sites were
located on dry, rocky slopes at elevations ranging from 1,890
to 1,980 m (6,200 to 6,500 ft). Trees were approximately 200
to 400 years old, and there were few understory plants of any
kind. Additional information on the pinyon-juniper portion
of the study area can be found in a discussion of ecological
units within the Green River corridor, Daggett County,
Utah (Goodrich, these proceedings).
Other forest habitats sampled were ponderosa pine (Pinus
ponderosa), aspen (Populus tremuloides), Douglas fir
(Pseudotsuga menziesii), lodgepole pine (Pinus contorta),
spruce/fir (Picea engelmannii / Abies lasiocarpa), mixed lodgepole/spruce/fir, and riparian woodlands (dominated by cottonwood trees, but often mixed with one or more of the
previously listed conifers). Sample sites for these forest
habitats were on the Ashley National Forest, immediately
west and south of the Flaming Gorge NRA. All sample sites
were occupied by mature to old stands of trees. Elevation
ranged from about 1,980 m (6,500 ft; ponderosa pine sites) to
nearly 3,300 m (10,800 ft; spruce/fir sites).
Methods
In: Monsen, Stephen B.; Stevens, Richard, comps. 1999. Proceedings:
ecology and management of pinyon-juniper communities within the Interior
West; 1997 September 15-18; Provo, UT. Proc. RMRS-P-9. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
Kathleen M. Paulin is a Wildlife Biologist with the Ashley National Forest,
355 N. Vernal Avenue, Vernal, UT 84078. Sarah R. Dewey is a Biological
Technician at the same address. During the study, Jeffrey J. Cook was a
Biological Technician with the Wasatch/Cache National Forest, 8236 Federal
Building, 125 S. State Street, Salt Lake City, UT 84138; current address is 300
Fernhill Drive, DeBarry, FL 32713.
240
Data in this paper were collected as part of the Ashley
National Forest's breeding bird monitoring program. Methods were based on point count protocols found in Ralph and
others (1993). We established 30 sample points in each of
eight forest habitats common in the study area, with points
divided among three distinct sites (stands) within each
habitat. All points were located at least 100 m from any edge
(change in cover type), and at least 200 m apart to avoid
USDA Forest Service Proceedings RMRS-P-9. 1999
are evenly distributed among all species present. Conversely,
Douglas-fir bird communities tend to be dominated by a few
abundant species. This causes it to have a lower index value
than pinyon-juniper, despite having similar numbers of
species and individuals.
The total individuals counted and diversity indices in
table 1 should be interpreted with caution. Bird densities in
pinyon-juniper habitats are believed to be strongly influenced by juniper berry production, which can vary widely
from year to year (Sieg 1991). Because we only have 1 year
of bird data and did not make any estimates of berry
production, we cannot say whether our results represent a
peak or a low in bird numbers. We can say that pinyonjuniper is able to support a relatively high number and
variety of birds, compared to other forest habitats in the
study area, in at least some years.
Land managers must consider more than simply the
quantity of species each habitat contributes to a management landscape. A site that supports a few rare species can
be as important as one that supports many common species
when trying to maintain or enhance overall diversity. We
attempted to characterize each habitat we sampled in terms
of the uniqueness of its contribution to the landscape-level
avian diversity, compared to other habitats in the study. One
measure of uniqueness is the degree to which the various
bird communities overlap with one another. Table 2 shows
the results of pairwise comparisons using Sorenson's quotient of similarity (as described in Morrison and others
1992). This quotient is based solely on the presence or
absence of species, without consideration of abundance. The
quotient varies from zero (no overlap) to one (identical
species lists for each habitat). Pinyon-juniper shows relatively high overlap (0.658) with ponderosa pine, moderate
double-counting birds. Each point was read twice during the
1994 breeding season (mid-May through mid-July). Counts
were begun within 15 minutes of sunrise and completed by
10 a.m., to correspond with the period in which territorial
males are most vocal. Bird detections (by sight, song or call)
were recorded for 10 minutes at each point. All detections
were recorded, regardless of distance from the observer.
Results _ _ _ _ _ _ _ _ _ __
Total individuals counted, total species detected and diversity index values for each forest habitat are shown in
table 1. Not surprisingly, the riparian woodland sites ranked
first in all three categories. Many studies have shown that
riparian woodlands have higher vertebrate diversity than
adjacent upland sites (Finch and Ruggiero 1993). Our results simply confirm the importance of riparian areas as
wildlife habitat.
Among the seven upland forest habitats, pinyon-juniper
ranked second in total individuals and third in species
richness and diversity. The variety and abundance of bird
life in pinyon-juniper stands was comparable to that observed in Douglas fir, and considerably higher than in the
lodgepole, spruce and fir stands that dominate much of the
study area. In general, numbers of species and individuals
tended to decrease with increasing elevation.
The diversity index values followed a similar pattern, with
the exception oflodgepole pine and Douglas-fir. The ShannonWeaver index is a function of both species richness and
evenness (the distribution of individuals among the species
present). A relatively species-poor habitat such as lodgepole
pine can have a high diversity index ifthe indi vid uals coun ted
Table 1-Total species detected, total individuals counted and Shannon-Weaver diversity index by habitat.
Ponderosa
pine
Aspen
Pinyon!
juniper
Douglas
fir
Lodgepole
pine
Spruce!
fir
Mixed
conifer
Riparian
woodland
Species detected
Individuals counted
42
973
38
562
31
779
29
746
25
405
22
314
21
226
49
990
Diversity index
1.26
1.20
1.19
1.09
1.18
1.08
1.04
1.28
Table 2-Similarity of bird communities based on the proportion of species in common a .
Ponderosa
pine
Ponderosa pine
Aspen
Pinyon/juniper
Douglas-fir
Lodgepole pine
Spruce/fir
Mixed conifer
Riparian canyon
Number of index values
greater than 0.500
.575
.658
.676
.627
.469
.476
.462
Aspen
Pinyon!
juniper
Douglas
fir
Lodgepole
pine
Spruce!
fir
Mixed
conifer
.575
1
.464
.627
.698
.567
.542
.598
.658
.464
1
.533
.429
.415
.385
.300
.676
.627
.533
.704
.627
.680
.385
.627
.698
.429
.704
1
.638
.609
.405
.469
.567
.415
.627
.638
.476
.542
.385
.680
.609
.791
.791
.366
.371
6
2
6
5
4
4
4
aCalculated as Sorenson's quotient of similarity: OS
found in both habitats
=2c/(a+b) where a = number of species in habitat a, b = number of species in habitat band C -
USDA Forest Service Proceedings RMRS-P-9. 1999
Riparian
woodland
.462
.598
.300
.385
.405
.366
.371
1
number of species
241
Table 3-Proportion of each forest bird community comprised of obligate or semi-obligate species. a
Percentage of
obligate species
Percentage of
semi-obligate species
Total obligates and
semi-obligates
Mixed
conifer
Riparian
woodland
Ponderosa
pine
Aspen
Pinyonl
juniper
Douglas
fir
Lodgepole
pine
Sprucel
fir
9.5
13.2
19.4
3.4
4.0
4.5
0
36.7
23.8
15.8
19.4
10.3
4.0
9.1
14.3
18.4
33.3
29.0
38.8
13.7
8.0
13.6
14.3
55.1
aObligate: only detected in one forest type; semi-obligate: only detected in two forest types.
overlap (0.533) with Douglas fir, and low overlap (less than
0.500) with all other forest habitats. In contrast, each ofthe
other upland forest habitats has moderate to high overlap
with at least four other habitats. The mix of bird species
found in pinyon-juniper appears to be uncommon within the
study area.
Another measure of uniqueness is the rarity ofthe species
occurring within each habitat. Table 3 shows the percentage
of species in each bird community that was restricted tojust
one habitat (obligate species), or shared between only two
habitats (semi-obligate species). Of the 31 species detected
in pinyon-juniper habitat, 12 (38.8 percent) fit into one of
these two categories. Only the riparian woodland sites had
a higher percentage of obligate and semi-obligate species.
Thus, not only is the particular combination of bird species
found in pinyon-juniper habitats distinctive, a relatively
high percentage of those species are rare or absent from the
rest of the study area.
Species we classified as pinyon-juniper obligates were
ash -throated flycatcher (Myiarchus cinerascens), bl ue-gray
gnatcatcher (Polioptila caerulea), Bullock's oriole (Icterus
bullockii), pinyonjay (Gymnorhinus cyanocephalus), western scrub-jay (Aphelocoma coerulescens), and Virginia's
warbler (Vermivora virginiae). Semi-obligate species that
were most abundant in pinyon-juniper were juniper titmouse (Baeolophus ridgwayi),' gray flycatcher (Empidonax
wrightii), and black-throated gray warbler (Dendroica
nigrescens). Semi-obligates that were less abundant in
pinyon-juniper than in their second habitat were spotted
towhee (Pipilo maculatus), violet-green swallow
(Tachycineta thalassina), and white-breasted nuthatch
(Sitta carolinensis). Although we did not attempt to define
an ecological basis for these apparent habitat preferences,
our list agrees well with obligate and semi-obligate species
lists published elsewhere (Fitton 1989; Cherry 1982) and
probably does reflect the importance of some specific habitat features found in pinyon-juniper sites.
Discussion --------------------------------Not surprisingly, we found pinyon-juniper bird communities to be different from those of most other forest habitats we sampled. Pinyon-juniper has obvious structural
and vegetative differences from the tall pine, spruce, and fir
forests of northeastern Utah's mountains, or from moist,
highly productive aspen and cottonwood stands. But it may
have surprised some to learn that the "pygmy forest,"
occupying poor sites and monotonously homogenous in its
242
composition and growth form, outranks many more stately
forests in the abundance and variety of birds it supports.
Designating some tracts of mature pinyon-juniper for retention is clearly a good investment for any manager
interested in maintaining biodiversity on his or her management landscape.
We compared bird communities from a variety of mature
forests. However, the choice facing managers is rarely which
forest to manage for on a given site. Most often, it is a
question of which seral stage ofthe existing forest is desired.
We did not sample early seral pinyon-juniper habitats, but
we can offer some insights from other bird studies. Sedgwick
and Ryder (1987) compared bird use of chained and unchained plots and found that chaining negatively affected
abundance of cavity nesters, timber gleaners, aerial foragers, and species that foraged or nested in foliage. Birds that
nested or foraged on the ground were found to use both
treated and untreated plots, so in effect no group was
benefitted by treatment. Likewise, Sieg (1991) found significantly higher bird numbers and species richness in pinyonjuniper woodlands than in adjacent grasslands. Both studies attributed the difference in bird use to the vertical
structure of the woodlands, which provided niches not found
in open habitats.
This does not mean that pinyon-juniper treatments are
always bad for birds. Cherry (1982) noted that slightly more
bird species nested in late seral pinyon-juniper stands, but
slightly more species foraged in early seral stands. This
suggests that creating a mosaic of seral stages will provide
the best balance of habitat features sought by birds. Sedgwick
and Ryder (1987) indicated that shrub-dependent and edgeassociated species can benefit from well-designed pinyonjuniper treatments. They recommended selecting sites that
have good potential for shrub growth, leaving lots of woody
slash, designing treatment units with a high edge-to-interior ratio, and using a varying levels of treatment so that
more trees are left standing toward the edges of units. All of
these measures will add structural complexity to the treated
unit, thus compensating in part for the loss of the pinyonjuniper overstory. Such treatment units will be more versatile as wildlife habitat than units stripped clean of wood and
seeded with grasses.
Although the discussion has so far focused on breeding
season, managers may wish to consider habitat values at
other times of the year. Sieg (1991) monitored bird use of
pinyon-juniper throughout the year and found that it supported more birds in every season than the neighboring
grasslands did. She speculated that the combination of
readily available food (from cones and berries) coupled with
USDA Forest Service Proceedings RMRS-P-9. 1999
good thermal cover made it especially attractive to birds in
the win ter. Cover val ues also make pinyon -j uni per a cri tical
element of big game winter range (Davis, these proceedings). Again, a landscape mosaic that intersperses cover
patches with openings providing foraging and browsing
opportunities may be the best way to meet an array of
management objectives.
Conclusion ---------------------------------Pinyon-juniper woodlands support a rich and distinctive
bird community, which makes a substantial contribution to
landscape-level avian diversity. Land managers should consider the habi ta t val ues of rna ture woodlands w hen planning
pinyon-juniper removals to meet watershed and forage production objectives. The best management option will likely
be a landscape that is thoughtfully designed to include
functional patches of all seral stages.
References ---------------------------------Cherry, Marion B. 1982. The effects of pinyon-juniper chaining on
wildlife of the Fillmore Ranger District, Fishlake National Forest. M.S. thesis. Logan, UT: Utah State University, Department
of Range Science. 114 p.
Davis, James N. These proceedings. The importance of pinyonjuniper woodland as big game critical winter range in Utah. In:
Monsen, Stephen B.; Stevens, Richard; Tausch, Robin J.; Miller,
Rick; Goodrich, Sherel, comps. 1998. Proceedings: ecology and
USDA Forest Service Proceedings RMRS-P-9. 1999
management of pinyon-juniper communities within the Interior
West; 1997 September 15-18; Provo, UT. Proc. RMRS-P-OOO.
Ogden, UT: U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station.
Finch, Deborah M.; Ruggiero, L. F. 1993. Wildlife habitats and
biological diversity in the Rocky Mountains and northern great
plains. Natural Areas Journal. 13(3):191-203.
Fitton, Sam. 1989. Nongame species accounts: the Utah juniper
obligates. Lander, WY: Wyoming Game and Fish Department. 48 p.
Goodrich, Sherel. These proceedings. Multiple use management
based on diversity of capabilities and values within pinyonjuniper woodlands. In: Monsen, Stephen B.; Stevens, Richard;
Tausch, Robin J.; Miller, Rick; Goodrich, Sherel, comps. 1998.
Proceedings:ecology and management of pinyon-juniper communities within the Interior West; 1997 September 15-18;
Provo, UT. Proc. RMRS-P-OOO. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Rocky Mountain Research Station.
Morrison, Michael L.; Marcot, B. G.; Mannan, R W. 1992. Wildlifehabitat relationships: concepts and applications. Madison, WI:
University of Wisconsin Press. 343 p.
Ralph, C. J.; Geuppel, G. R; Pyle, P.; Martin, T. E.; DeSante, D. F.
1993. Handbook of field methods for monitoring landbirds. Gen.
Tech. Rep. PSW-GTR-144. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 41 p.
Sedgwick, James A.; Ryder, R A. 1987. Effects of chaining pinyonjuniper on nongame wildlife. In: Everett, R L., compiler. Proceedings: pinyon-juniper conference. 1986 Jan. 13-16, Reno, NV. Gen.
Tech. Rep. INT-GTR-215. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 581 p.
Sieg, Carolyn H. 1991. Rocky Mountain juniper woodlands: yearround avian habitat. Research paper RM-296. Fort Collins, CO:
U.s. Department of Agriculture, Forest Service, Rocky Mountain
Forest and Range Experiment Station. 7 p.
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