SUMMER HABITAT USE AND SELECTION BY FEMALE SAGE GROUSE (CENTROCERCUS UROPHASIANUS) IN OREGON

6 Pages·1993·2.4 MB·English

by  Michael A Gregg

GreatBasinNaturalist53(3), pp.293-298
SUMMER HABITAT USE AND SELECTION BY FEMALE SAGE GROUSE
{CENTROCERCUS UROPHASIANUS) IN OREGON
Michael A. Cretig',John A. Crawford-, and Martin S. Dnit-
—
Abstr.\CT. Cover t\pes and \egetati\e characteristics (e.g., grasst's, rorl)s, sIuuIjn) used h\- female Sage (;r()use
[Centrocercus urophasianus) during summerwere comparedwith a\ailal)le habitat on tsvo studyareas in southeastern
Oregon. Broodlesshens,whichconstituted 114ofthe 125(91%)radio-markedhensstudied, selectedbig(Arteiimiatri-
dentata subspp.) and low sagebrush (A. arbuscula) covertypes at both stuch- aieas. At Hart Mountain, broodless liens
didnotselectspecificvegetativecharacteristics within covertypes. However, atJackass Creek, forbcoverwas greater
(P = .004)atbroodlesshen sites than at random locations. Differences in habitat useb\ broodless hensbetween stud\-
areas were associatedwith differences in torb availability. Broodless hens used agreaterdiversit\- ofcover types than
hens \\'ith broods. Broodless hens gathered in flocks and remained separate from but near hens with broods during
earl\ summer. Byearl\'Julyliroodlesshensnio\edtomeadowswhilehenswitli broodsriMuainedin u[)landhaliitats.
Keywords: SageGroiLse. Centrocercus urophasianus, Oregon, fi'indli'. hnxxllesslien.s. Iiulntut. iiiorniwnts. .'unniner.
broods, use,selection.
Productivity of Sage Grouse {Centrocercus tions, and to assess habitat use by broodless
urophasianus) is among the lowest of North hens in relation to hens with broods on two
American grouse (Edminster 1954:130). stud)' areas.
Reported nest failure ranged from 76% in
Oregon (Batterson and Morse 1948) to 36% Study Ahea.s
(Wallestad and Pyrah 1974) in Montana. Con-
sequently, a relatively large percentage of The stud)' areas were located in southeast-
summer Sage Grouse populations consists of ern Oregon at Hart Mountain National Ante-
broodless hens. However, information on lope Refuge (Lake County) and at Jackass
broodless hens is largely anecdotal. Only Creek (Harnc) County). Topography at both
observations of the pro.ximity of broodless areas consists of flat sagebrush plains inter-
hens to hens with broods (Dalke et al. 1963, rupted b)- rolling hills, ridges, and draws. Ele-
Martin 1976) and chronology of summer vations range from 1500 to 2450 m at Hart
movements by broodless hens (Petersen 1980, Mountain and from 1200 to 1700 ni at Jackass
Conn(4K' et al. 1988) have been reported. No Creek. Vegetation at both areas is dominated
stud)' has dealt specifically with habitat use by bv low sagebrush [Artemisia arbuscula), big
broodless Sage Grouse. sagebrush (A. tridentata vaseijana, A. t.
We investigated habitat use by broodless wijomingensis, andA. t. tridentata), green rab-
hens on a hierarchical order of selection bitbrush {Chrysothamnus ciscidiflorus), and
(Johnson 1980). We hypothesized that brood- western juniper ijuniperus occidentalis).
less Sage Grouse selected cover types (third- Stands of cm-1-leaf mountaiii-niahogain- iCer-
order selection) and vegetative characteristics cocarpus ledifolius) and (}uakiug aspen {Popii-
within cover types (fourth-order selection) lus tremuhndes) occur onl)- at Hart Moiuitaiii.
and that selection differed between broodless Conunon annual and perennial forbs include
hens and hens with broods. Our objectives mountain-dandelion {Agoseris spp.), milk-
were to identify cover types used by broodless vetch {Astragalus spp.), hawksbeard {Crepis
hens in relation to availability, to identifv' veg- spp.), lupine {Lupinus spp.), and phlo.x {Phlox
etative characteristics at broodless hen sites spp.). Grasses consist largely ofbluegrass {Poa
and compare those to randomly selected loca- spp.), bluebunch wheatgrass {Agropijron
'U.S.FisliandWikllili-Si-nice,Bci\HI.Lakeview.Orfgon97630.
-Dt-partnu-iitofFislu-riesandWildlilc.OirgonStateUni\ersit>,Conallis.Ori-goii973.31-3803.
293
294 Ghi:at Basin Naturalist [Volume 53
spicatitm), needlegrass (Stipa spp.), fescue We characterized vegetation at sites used
{Festuca spp.), giant wildrye {Elymu.s b\' broodless hens within two days after visual
cinereiis), and bottlebrush squirreltail (Sitmi- locations were determined. Canopy cover (%)
lon hystrix). Plant nomenclature from Hitch- of shrubs was measured by line intercept
cockand Cronquist (1987)was used. (Canfield 1941) along two 10-m perpendicular
transects intersecting at the broodless hen
site. The position of the first transect was
Mkthods
determined from a randomb- selected com-
pass bearing. Each shrub intercepted was
Female Sage Grouse were captured
(Giesen et al. 1982) during summer 1988, p(l<a4c0edcmi)n,tomoendeioufmth(r4e0e-8h0eicgmh)t,cloarssteasl:l (sh>o8r0t
spring and summer 1989-90, and spring 1991. cm). Canopy cover of shrubs was recorded
Kach hen was fitted with a numbered alu- separately for each height class. Cover (%) of
minum leg band and a poncho-mounted, forbs and grasses was estimated in five 20 X
solar-powered radio transmitter with a nickel-
50-cm plots equidistantly spaced along each
cadmium l)attcry (Amstrup 1980). Radio- transect (Daubenmire 1959). Vegetation was
marked hens were monitored during summer
characterized at randomK' located points dur-
(June-August) 1989-91 at an average rate of ing June and JuK with the same methods
no more than twice monthly to minimize the used to measure variables at broodless hen
problem associated with lack ofindependence sites. Random sites were located with a ran-
oflocations. Furthermore, we recaptured and dom numbers table, which was used to deter-
remoN(.'d radios from hens at the conclusion of mine starting point, compass bearing, and dis-
each field season, and pre\'iousl\' unmarked tance traxeled.
hens were fitted with radios for use in subse- We compared the use of cover types by
{{uent \ears to maintain independence ofsam- broodless hens with availability ofcover types
ples among years. Nevertheless, we acknowl- within study areas from June through August.
edge there may be a potential bias in the use The proportions ofcover t\'pes available were
of re-observations, even at a low rate of Ire- used to establish the expected \'alues for fre-
(juency, of the same indixidiuils within a quency of bird observations occurring in
breeding season. those cover types. We also compared cover
All locations of radio-marked hens were t)pe use between broodless hens and hens
mapped as Universal Transverse Mercator with broods. Chi-square analysis was used for
coordinates. Visual locations of radio-marked these tests. Co\er t\pes with expected values
broodless hens were marked and served as of <5 bird observations were combined and
sites for vegetation sampling during Jime and analyzed collectively. If differences were
July 1990. Date, location, and flock size of detected, confidence intenals were calculated
broodless hens and hens with broods to identify cover tvpes that contributed to the
observed on each study area were recorded. difference (Neu etal. 1974, Byers et al. 1984).
Definitions of monthly time periods were We used a factorial analysis of variance
early (first 10 days), mid (middle 10 da>s). and (ANOVA) (PROG GLM, SAS Institute, Inc.
late (last 10 days). 1989) to compare \egetati\'e characteristics
Eleven cover types were defined on the among plot types (broodless hen or random).
basis ofdominant shrubs and grasses (Gregg Study area was an additional factor in the
1992). We used color infrared aerial pho- ANOVA model to account forvariation associ-
tographs and topographic maps to delineate ated with spatial differences (Snedecor and
co\er types on each stud\ area. Each hen Cochran 1967:339). A significant plot t\'pe
location was classified into 1 of the 1 1 cover (hen use site or random location) X stud\ area
t>pes. At each study area available habitat was interaction (F = .02) was detected tor (orb
determined with the mininuuu convex poly- cover. Consequently, differences among plot
gon method (Odum and Kuenzler 1955) from t\pes for forb cover were reported by study
telemetr\ locations obtained during summer. area. A single-factor ANOVA was used to
Proportions of cover types within the avail- compare vegetative characteristics at random
able habitat at each area were determined locations between study areas in co\er t\pes
with adot grid s\stem (AveiT 1977). used bv broodless hens. We assumed our data
1993] HAiuTvr UsK BY Fkmai.e Sack Chol'se 295
MoTuanbtalien1.NaUtsieon(a7lf)AonitceloomptelR\epcf.usgdemi(nnt=;s6u7imhieKn-sr.(1Ji6i8iKl'o-Acuajtjiioinsst))aInndraJcalcikoa-isnsarCkrie'dekl)i((n)()=ilk4-s7s lSiaetnjsf,(;1n3)7iilsofcaltiii'oiinss)atsltluadr\l
areas. LakeandHarne\ counties,Oregon, 1989-91.
"IiK'ludfSbasinbigsagrlirusli.lakcluil.amitiioiintaiiislinili
"UsfclillcTfil(/'<.0.5,fromavail.iliilitv.
296 Great Basin Naturalist [Volume 53
TvBLli2. Use(%)ofc()\crtvpes duringsummer(June-August)byradio-markedfemale SageGrouse at Hart Moun-
tain NationalAntelope RefugeandJaekassCreekstudyareas. LakeandHarneycounties,Oregon, 1989-91.
;
1993] H \Hirvr I'si", by Fi:\iai.k Sack (^hoise 297
Table 4. \i'iii.tati\c iliaiacttrislics (/;? comt) at raiuloiii locations at Hart Mountain National Anti-IojH' Ht-I'imc and
jackass(licck stntK areas. Lakeand Ilanic\ counties, Oici^on.JniicandJnly 1990.
Hart Mountain JackassCrci'k
in = 30) fii = 70)
(iliaractcristic /'\ SD .SD
Fori)co\'ei" .0001
Grasscover .0001
Shriihco\t'r
Short. <4()cm .ooos 19 12
Medium.4()-S()ci .25 6 9
Tall. >S()cm .OOOfi 1 4
chroiioloiix of .sumnier niovemcnts 1)\ blood- ment, ihroiigli a research contract adiiiiiiis-
less hens (Batterson and Morse 194.S, Dalke et tered 1)\ the Oregon Department ol l-1sh and
al. 1963, Martin 1976, Connelly et al. 1988). Wildlife. Logistical support was supi)Iied l)\
Petersen (1980) reported that the early nio\e- the U.S. Fish and Wildlife Service. We thank
ment to meadows bybroodless hens was relat- J. K. Barnett and .\. K. DeLong for assistance
ed to nest loss and not desiceation of vegeta- with data collection. W". D. Fdge. S. L. Olson-
tion in uplands. Contrastingly, Sehoenberg Edge, and R. L. Jarvis proxided ciitical
(1982) noted that summer movements by reviews of the manuscript.
broodless hens andhens with broods occurred
simultaneousK' and were prol)ably a response
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uplands. .\\isiiup, S. C. 1980. \ radio-collarforgame liirds. Jour-
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