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SHORT COMMUNICATIONS
1978. The ecology and behaviorof the
PrairieWarblerDendroicadiscolor.Ornithol.Monogr. 26.
PRESTON, F. W. 1948. The cowbird (M. ater) and the
cuckoo (C. canorus).Ecology 29:115-116.
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796-807.
ROTHSTEIN, S. I. 1975. Mechanismsof avian egg recognition:do birdsknowtheirown eggs?Anim. Behav.
23:268-278.
ROTHSTEIN, S. I. 1978. Mechanismsof avian egg-recNOLAN, V., JR.
111
ognition: additional evidence for learned components. Anim. Behav. 26:671-677.
VICTORIA,
J. K. 1972. Clutchcharacteristics
andeggdis-
criminationabilityof the AfricanVillageWeaverbird
Ploceuscucullatus.Ibis 114:367-376.
L. H. 1949. Twenty-fiveeggs apparently
WALKINSHAW,
laid by a cowbird.Wilson Bull. 61:82-85.
RockefellerUniversityField ResearchCenter,Millbrook,
New York12545. Received 31 August 1981. Final acceptance 7 May 1982.
Condor85:111-113
? The Cooper Ornithological Society 1983
SEASONALVARIATION IN NEST
PLACEMENTOF ABERT'S
TOWHEES
DEBORAHM. FINCH
Several meteorologicalvariablesare known to influence
the heat budgetsof nestingbirds(e.g., Walsbergand King
1978a, b). Such factorsinclude air temperature,incident
radiation,wind, and humidity.If the microclimateof the
nest is unfavorable,parentbirdsmay become inattentive,
exposingeggs or nestlingsto excessive heat or cold. They
may then desertthe nest and their offspringmay die. To
improvethe probabilityof nestingsuccessfully,many Old
Worlddesertbirdsplacetheirnests so as to receivemorning sunlight (Maclean 1976). Several investigatorshave
demonstratednonrandomorientationof hole entrancesof
New Worldcavity-nestingbirds(Ricklefsand Hainsworth
1968,Inouye 1976,Inouyeet al. 1981), butfew have tested
for the significanceof nonrandomplacementor variation
in placementbetweenseasonsof opennests.Maclean(1976)
indicatedthat larksin the KalahariDesert orientedtheir
nests to receiveshadein summerand sun in winter.Balda
and Bateman (1970) predictedthat Pinyon Jays (Gymnorhinuscyanocephalus)in Arizona may place firstnests
of the seasonon the sunnysides of ponderosapines (Pinus
ponderosa),but that they may orientlaternests more randomly. They showed that these trees in Marchwere 30C
warmeron the south side than on the north side, and that
the jays selectednest sites to gain more heat:all jay nests,
regardlessof season, had a significantsouthwardorientation. I reportherea secondtest of Baldaand Bateman's
(1970) hypothesis,usingdata for a birdof hotterclimates,
the Abert'sTowhee(Pipiloaberti).This sedentaryspecies
inhabits only desert riparianregionsof the southwestern
United States,whereasthe mobile Pinyon Jay occupiesa
greaterelevationaland latitudinalrange,thoughbreeding
chiefly in foothills and lower mountain ranges.Because
nestsof the Abert'sTowheearetypicallyexposedto higher
springand summertemperaturesthanthose of the Pinyon
Jay, a secondtest of Baldaand Bateman'spredictionmay
demonstrategreaterseasonalvariationin nest placement.
The study was conductedin honey mesquite(Prosopis
glandulosa)habitaton the ColoradoRiver Indian Reservation 10 km northof Ehrenberg,Arizona.FromJanuary
to July 1980, I spent 15 h each week (84 5-h searches)
looking for nests on, or near a griddedstudy plot of 20
ha. Field workterminatedin Julywhen no new nestswere
started.
The Abert'sTowheesin my studyareabuilt their open
nests in mesquite,willow (Salix goodingii),exotic salt cedar(Tamarixchinesis),saltbush(Atriplexlentiformis),in-
kweed (Suaeda torreyana),arrowweed(Tesseriasericia),
and mistletoe (Phoradendroncalifornicum),a parasiteof
mesquite(Finch 198la). Nests built in Marchwere constructed of mesquite bark, saltbush, salt cedar and arrowweedleaves, grassesand even newspaper.Laternests
were made predominantlyof mesquiteleaves, which became availablein April (Finch 1981a).
Compassdirectionof the nest with respectto the main
trunksof mesquites,willowsand salt cedarswas recorded
for 52 nests. I did not include nests built in small shrubs
because compass directions were difficult to determine
accurately.Nests were allocatedto early and late seasons
by dividing in half the number of days of the observed
breedingseason(118 days fromfirstto last nest initiated).
The RayleighZ test (Batschelet1965)was used to test for
randomnessof nest concentrationof early and late nests,
and Batschelet's(1965:33)parametrictwo-sampletest applying the F-statistic was used to test for a differencein
mean directionbetweenearlyand late nests. Information
on solarpathsand prevailingwind directionsin the lower
ColoradoRiver valley was providedby the Laboratoryof
Climatology,ArizonaState University, Tempe.
The resultsindicate that the placementsof early nests
were more concentratedthan late nests (Table 1). Their
distributionwas significantlyunimodal with a preferred
southeastdirection,whereasthe distributionof late nests
hada nonsignificantnorthwestwardorientation.The mean
directionsof earlyand latenestsweresignificantlydifferent
(F5(so,= 14.82,P < 0.001). Becausethe distributionof late
nest orientationswas nonsignificant,the value of this twosample test may be lessened. The Rayleigh tests nevertheless confirmthe differencein the distributionsof nest
orientations.The circulardistributionsof early and late
nests are shown in Figure 1.
These resultssuggestthat Abert'sTowhees place their
nests in response to environmentalfactors that are importantonly duringthe first half of the breedingseason.
In the lower ColoradoRiver valley, the sun rose at 890
(almostdue East)in March1980 and traversedthe south-
TABLE 1. Orientationof Abert'sTowhee nests with respect to the main trunkof the tree.
Season
Number
of nests
Nest concentrationa
Rayleigh's
Z testb
Mean
directionc
Early
Late
24
28
0.367
0.205
3.23
1.18
1300 ? 690
3210 ?+ 720
a A value of I indicates all nests were placed in precisely the same direction,
and a value of 0 indicates a uniform distribution.
bRayleigh's Z test (Batschelet 1965) shows that the distribution of early
nests was significantly unimodal (P < 0.05), whereas the distribution of late
nests was random (P > 0.05).
c Standard deviation is included.
112
SHORTCOMMUNICATIONS
Early
00
n=24
2700
0*-
9
o
Lote
??
/, 1800*180?
i
N
0"
0
"0
Late
270
-
II
0
0? n = 28
0o
n 0=28
0
180?
0
90
?I
0
0
0
270
-900
04
0 0
?
180
FIGURE I. Compassorientationof earlyand late nests
in the lower ColoradoRiver valley.
ern hemisphereof the sky; the elevation of the sun from
the horizon was only 58*at solar noon. In June, the sun
rose at 6 l*NEand was almostdirectlyoverhead(8 1 from
closest horizon)at solar noon. Earlynests of Abert'sTowhees that were placed on the southeast sides of trees
receivedmaximumincidentradiationin the morning,when
the air was cool. As the breedingperiod progressedto
rosefrom23.80C
August,meanmaximumairtemperatures
to 42.90C(Finch 198la), and nest placementthat allowed
rapidheat gain presumablybecameless adaptive.Late in
the season, nests tended to be placed northwestwardly
although the distributionwas not significant.Warmer,
southeasternnests may reduceadult and nestlingenergy
expensesearly in the season, whereaslater, northwestern
nests may protectembryosfrom potentiallylethalradiant
heat (Bennett and Dawson 1979) and/or prevent high
evaporativewaterlosses from parentsand offspring.
Wind direction may also influencenest placement of
Abert'sTowhees. A nest on the lee side of a tree may be
betterprotectedfrom cooling or destructivewinds. From
MarchthroughMay of 1980, the prevailingwind directions were from west-northwest,but from June through
Septemberthe prevailingwinds were from south-south-
east. Southeastwardly
placednests in springwereshielded
from the greatestproportionof winds (in contrast, see
Balda and Bateman's 1970 study). Summer nests were
apparentlyplaced randomlywith respectto wind direction. For a dark-plumagedbird like an Abert'sTowhee,
convectiveheatloss via feathererectionin wind may even
be a principalmeansof coolingduringthe desertsummer
(Walsberget al. 1978).
Earlynests of Abert's Towhees were thereforeplaced
advantageouslyrelative to both solar radiationand prevailing winds. The relativeimportanceof either of these
factorswas not determined.Becauseconcentrationof late
nestswas not significantlydifferentfromrandom,it seems
likely that either (1) air temperatureand wind did not
influencenest site selectionand nestingsuccesslate in the
season (e.g., air temperaturemay have been identicalon
all sides of the tree as indicated by Balda and Bateman
1970), (2) the probabilityof reproductivesuccesswas independentof nest site placement,or (3) towheesused other, less obvious, methodsof selectingnest sites (e.g.,Walsberg 1981).
Nesting success of the towhees descreasedduringthe
season(Finch 198la), associatedwith an influxof BrownheadedCowbirds(Molothrusater).The pressuresof cowbird parasitismor predation(Finch 1981
lb, 1982a) may
have overriddendecisions to place nests primarilywith
regardto microclimaticconditions (see Best and Stauffer
1980:153).As the season progressed,towhees spent less
time locating and constructingnests (Finch 1981
la) and
even built some nests that fell apart (pers. observ.). In
addition, they confiscatedabandonednests of their own
or other species (Finch 1982b). This apparent inclination to "save time" at the end of the breedingperiod
suggeststhat they took less care in selecting nest sites.
When compared with an overwhelmingprobability of
nestingfailurecausedby predationand brood parasitism
(approximately 95%; Finch 1981a), a less-than-satisfac-
tory microclimateat a late nest may have negligibleeffect
on the productivityof Abert'sTowheesin the lower Colorado River valley.
I thank C. J. Henny, F. L. Knopf, and H. Kruegerfor
reviewingthis manuscript.I am gratefulto the Colorado
River Indiantribesfor permissionto work on their land.
LITERATURECITED
R. P., ANDG. C. BATEMAN.
1970. The breeding
BALDA,
biology of the Pifion Jay. Living Bird 11:5-42.
E. 1965. Statisticalmethodsforthe analysis
BATSCHELET,
of problems in animal orientationand certain biologicalrhythms.AmericanInstituteof BiologicalSciences, Washington,DC.
A. F., ANDW. R. DAWSON.
1979. Physiological
BENNETT,
responsesof embryonicHeerman'sGulls to temperature. Physiol.Zool. 52:413-421.
1980. Factorsaffecting
BEST,L. B., ANDD. F. STAUFFER.
nestingsuccessin riparianbirdcommunities.Condor
82:149-158.
FINCH, D. M. 198la. Variationin the reproductiveecology of the AbertTowhee.M.Sc.Thesis,ArizonaState
Univ., Tempe.
D. M. 1981b. Nest predationof Abert'sTowhees
FINCH,
by coachwhipsand Roadrunners.Condor83:389.
D. M. 1982a. Rejectionofcowbirdeggsby Crissal
FINCH,
Thrashers.Auk 99:719-724.
D. M. 1982b. Interspecificnest use by arid-land
FINCH,
birds. Wilson Bull 94:582-584.
INOUYE,D. W. 1976. Nonrandom orientation of entranceholes to woodpeckernests in aspentrees. Condor 78:101-102.
ANDD. W. INOUYE.1981.
R. S., N. J. HUNTLY,
INOUYE,
Non-random orientationof Gila Woodpeckernest
entrancesin SaguaroCacti. Condor83:88-89.
G. L. 1976. Arid-zoneornithologyin Africa
MACLEAN,
SHORT COMMUNICATIONS
and South America.Proc. XVI Int. Ornithol.Congr.
(1974):468-480.
RICKLEFS,R. E., AND F. R. HAINSWORTH.1968. Temperaturedependent behavior of the Cactus Wren.
Ecology49:227-233.
WALSBERG, G. E. 1981. Nest-site selection and the radiative environmentof the WarblingVireo. Condor
83:86-88.
WALSBERG,G. E., E. S. CAMPBELL,AND J. R. KING. 1978.
Animal coat color and radiativeheat gain:a re-evaluation. J. Comp. Physiol. 126:211-222.
WALSBERG,G. E., AND J. R. KING. 1978a. The heatbud-
113
get of incubatingMountainWhite-crownedSparrows
(Zonotrichialeucophrys)in Oregon.Physiol.Zool. 51:
92-103.
G. E., ANDJ. R. KING. 1978b. The energetic
WALSBERG,
consequencesof incubationfor two passerinespecies.
Auk 95:644-655.
U.S. Departmentof Agriculture,Rocky MountainForest
and Range ExperimentStation, 222 South 22nd Street,
Laramie, Wyoming82070. Received 27 February1982.
Final acceptance24 July 1982.
Condor85:113
? The Cooper Ornithological Society 1983
FLIGHT SONG AND SONG FLIGHT
IN THE ORANGE-CROWNED
WARBLER
WILLIAMM. GILBERT
Birds of many species commonly sing while flying. The
behavior is characteristicof many open-countryspecies,
such as larks, pipits, and Bobolinks (Dolichonyx oryzivorus)and also occurs among some woodland species,
including several wood warblers(Parulidae;Ficken and
Ficken 1962). In some of these warblerspecies, both the
songgiven duringflight,and the flightitself, are distinctly
differentfromperchsongand "normal"directflight.Ficken and Fickendescribedsuch songs as "usuallya variable
warbling[accompaniedby a] rising flight on slowly flapping or quiveringwings [and]typicallya directand silent
descent."
Workershave reported"flightsongs"and "songflights"
occurringin several species of Vermivora,includingthe
Tennessee Warbler(V. peregrina;Bowdish and Philipp
BowlesandBowles
(V ruficapilla;
1916),NashvilleWarbler(
1906, and Thayer, reported in Chapman 1907), Bachman's Warbler(V. bachmanii;Howell 1924, reportedin
Bent 1953), and Blue-wingedWarbler(V. pinus; Pitelka
1939). The songs and flightsdescribedfor these species,
however,appearto be less modifiedthan those described
by the Fickensfor non-Vermivorawarblers.
I observedflightsongs and song flightsoccurringin the
Orange-crownedWarbler(V. celata) during behavioral
studiesof the speciesin its typicalnestinghabitatin Contra
Costa County, central coastal California.I followed the
behaviorof unmatedterritorialmales priorto 12:00,during March,April, and May of 1980, 1981, and 1982. Although I may have overlookQdthe behaviors, I did not
observe flight songs and song flights in unmated birds
during late February,June, and early July, nor among
matedbirds duringany month. Populationsof these warblerswererelativelydensein my studyareas,with all males
having at least two territorialneighbors.Territorialdisputes were common.
Most flightsongs I heardwere begunin mid-flight,and
completed on a perch. Occasionallythe entire song was
renderedin the air. I could detect, by ear, no difference
betweensongs sung duringflightand those sung entirely
while perched.Whenin song flight,the wingsof a warbler
"fluttered"or "quivered"in a way I nevcharacteristically
er saw in normaldirect flight.I observednothingresembling the rising flightand direct descent describedby the
Fickens. I noted nine instancesof birds singingwhile in
flight during260 min of observationin which the individualOrange-crowned
Warblerswerein sight.Sincethese
birds usually sang four to six songs per minute, it is apparentthatflightsongsoccurredmuchless frequentlythan
perch songs. Flight songs and song flightsapparentlyoccurredat random,and I noticed no associatedspecialcircumstances,such as the presenceof a female or a competing male.
The flightsongs and song flightsI observedin Orangecrowned Warblersdifferedfrom those describedby the
Fickens.Theygenerallyresembledthose describedforother species of Vermivora,although the flutteringin song
flight has hitherto been reportedonly for the Nashville
Warbler(Bowles and Bowles 1906). I am aware of only
two reportsof song and flightbehaviorresemblingthose
I havereportedhereoccurringin parulidsotherthanspecies
of Vermivora.The AmericanRedstart(Setophagaruticilla) apparentlyhas an "unmodified"flightsong and song
flight often associated with encounterswith females or
rival males (Ficken 1962). The Kirtland'sWarbler(Dendroicakirtlandii)also has such songs and flights,but they
do not seem to be associatedwith any special environmental context (Mayfield1960:133).
Relatively unmodifiedflight song and song flight now
are reportedfor the majorityof North American Vermivora,suggestingthat these forms of behavior are characteristicof the genus.
LITERATURECITED
A. C. 1953. Lifehistoriesof NorthAmericanwood
BENT,
warblers.U.S. Natl. Mus. Bull. 203.
R. S., ANDP. B. PHILIPP.
1916. The Tennessee
BOWDISH,
Warblerin New Brunswick.Auk 33:1-8.
C. W., ANDJ. H. BOWLES.
1906. The Calaveras
BOWLES,
Warblerin westernWashington.Condor8:68-69.
F. M. 1907. The warblersof North America.
CHAPMAN,
Appleton& Co., NY.
M. S. 1962. Agonisticbehaviorand territoryin
FICKEN,
the AmericanRedstart.Auk 79:607-632.
M. S., ANDR. W. FICKEN.1962. The comparFICKEN,
ative ethologyof the wood warblers:a review.Living
Bird 1:103-122.
H. 1960. The Kirtland'sWarbler.Cranbrook
MAYFIELD,
Inst., BloomfieldHills, MI.
F. A. 1939. Flight song of the Blue-winged
PITELKA,
Warbler.Auk 56:340-341.
4630 DriftwoodCourt,El Sobrante,California94803. Received 22 February1982.Finalacceptance7 August1982.