CONDITION MODELS FOR WINTERING NORTHERN PINTAILS IN THE SOUTHERN HIGH PLAINS

6 Pages·1992·2.5 MB·English

by  Loren M Smith

Creat Basin Natur;ilist52(3),pp.226-231
CONDITION MODELS FOR WINTERING NORTHERN PINTAILS
IN THE SOUTHERN HIGH PLAINS
Lorcn M. Smith Douglas G. Sheelev", and Da\i(l B. Wester
,
—
AbstiucT. ThreeconditionmodelsiorwinteringNorthernPintails(Anasacuta)weretestedfortheirabiiit) topredict
fat mass, logarithmoffat mass, oraconditionindex (CI)incoiporatingfatmass. Equationsgeneratedtopredictfatmass
andthelogarithmoffatmassaccountedformorethan69%ofthevariationinthesedependentvariables.Logtransforma-
tionsofbodymass,winglength,andtotallengdiexplainedatleast60%ofthevariationinCI.Allmodelsperformedbetter
onanindependentdataset. Meanpredictionerrorwasminimal(<8%ofmeasuredvariables)andnegativeforallmodels.
Regression modelsapplytoliveanddeadpintails andthus representtoolsthathaveutilit)'in awidevariet)-ofstudieson
pint;ulcondition.
Ki-ifwords:Niiillirni Pintails. Anasacuta,Ixxli/n>ii(iitii>)i.predictivemodels. Texas, ivateifoiel.
Biologists have used variotis indices for regions in the Western Hemisphere (Bolen et
assessing waterfowl nutritional status. Initially, al. 1989). Twents'thousandpla\asarepresentin
onlybodymasswasused(Hanson 1962, Folket the SHPprovidingwinterhabitat forwaterfowl
al. 1966, Street 1975, Flickinger and Bolen (Haukos and Smith 1992). At least one-third
1979), butlaterstmcturalvariableswere incor- (>300,000)oftheNorthernPintailswinteringin
poratedto adjust forindividual size differences theCentralFK'w^aywdnterontheSHP(Bellrose
(Oven and Cook 1977, Bailey 1979, Wishart 1980).
1979). Ringelnian and Szvmczak (1985) and
Johnson et al. (1985) re\"iewed a\ian condition Methods
indicesandnotedthevalueofanaccurateindex
oflipids in migratoiy^ bird management. These Northern Pintails were collected using
studies noted that scaling moiphological \ari- deco\'s and b)' jtmip-shooting on plavas and
ableswithbody mass providedtisefulindicesto associatedtailwaterpits in the SHP from Octo-
avian bodycondition. ber through March of 1984-85 and 1985-86.
NorthernPintails{Anasaciifa)M-eoneofthe Tarsal length (measured from the junction of
most widespread waterfowl species in North the tibiotarsus and tarsometatarsus to the point
America(Bellrose 1980),butrecentlytheirpop- ofarticulation bet^veenthetarsometatarsusand
ulations have declined, making them a species middle toe, 0.01 mm), flattened wnng chord
of special concern (Smith et al. 1991). Our (measuredfrom theinsertionoftheahilatothe
objectives were to pro\ide an ecjuation to pre- tipofthetenth priman', 0.1 cm), andtotal body
dict total carcass fat (b()d>-condition) ofNorth- length (measured from the tip ofthe bill to the
ern Pintails and to test that index on an end of the p\'gost\le, thus avoiding complica-
independent data set. Theauatonn'cal \ariables tions due to tail feather growth, 0.1 cm) were
testedare suitable forfieldstudies. recorded for each bird. During 1985-86 an
additional wing measurement was recorded
from the insertion ofthe alula to the tip ofthe
Study Area
ninthpriman'becausetheninthprimarymaybe
slightK- longer than the tenth. Birds were
The stud\ was conducted in the Southern ])lucked and frozen.
High Plains (SUP) ofTexas, an82,88()-km-area Ingesta and intestinal contents were
that is one of the most intensixel)- cultivated remoxed in the laboratoiy. Birds then were
-^BDoexpa4r6t4m,eEnltdoorfa,RaInogweaa.n50d62W7i.ldlifeManagement,TexasTecliUi\iversi(\.I.iilihoek.TexasT9K)9.
226
1992] PlNTAII,C:()\'niTK)\ MODKLS 00'
TaHI.K 1.X'arialile.su.st'dinprcdictixcmodelsolIxxKcondition lorXortlicrn TiiitaiLs[Anasaciitd}ontlieSoiitlicrn IIi<j;li
Plain.s,Texas.
228 GreatBasin Naturalist [Volume 52
T.\BLE 2. Regression equations and associated statistics tor predicting carcass fat (model 1) content (g) in Northern
Pintiiils(Anasacuta)collectedontheSoudiemHighPlainsof'Texas,October-Mtuch 198-1—S6.
1
1992] PintailCondition Models 229
Table4.Regressionequationsandassociatedstatisticsforpredictinglogcarcassfat(model3)inNortlieniPintails(Anas
acuta)collectedontheSouthernHighPlainsofTexas,October-March 19S4-86.
Explanator)'variables
Equation Intercept LMASS LWING
3.1 .727 Parameterestimate —3.—410 3.412
(Adult male;/) = 140) SE —
N'iirianceinflation factor —
PartialR-
3.2 .693 Parameterestimate —1—.61
(Adultfemale;it = 69) SE —
\'iU"ianceinflationfactor —
PartialR-
3.3 .722 Parameterestimate —11.—066
(|u\eiiilemale;ii = .58) SE —
Vtirianceinflation factor —
PartialR-
3.4 .745 Parameterestimate —.5—.444
(Ju\enilefemale;n = 49) SE —
\'arianceinflationfactor —
Partialfi"
230 Great Basin Naturalist [Volume 52
associated with using body mass alone as an graphical range in which theywere developed.
indextoconditionofmigratorybirdshavebeen For comparisons between age and sex classes
noted (Bailev 1979, Wishart 1979, Iverson and weencourageuseofmodel3.Researchalsomay
Volis 1982. Johnson et al. 1985). Because indi- refjuire knowledge of absolute fat content.
viduals \aiy in stnictural size, bod\' mass will Importanceofaccuracyandprecisionwillaffect
reflect that \ariabilitA' in muscle and bone, in model selection. Care should be exercised to
addition tovariation in lipids. restrict model use to winter when changes in
Modelshavebeendexelopedthatpredictfat bod)' mass primarily reflect fluctuations in fat,
contentinwaterfowl,buttheserequiresacritice not fat-free diy mass (i.e., protein and mineral
anddissectionofthebird(Woodall 1978,Chap- fractions).
pell and Titman 1983, Thomas et al. 1983,
Whvte and Bolen 1984). These equations may Acknowledgments
incorporate skin (subcutaneous), abdominal
(omental), and/or intestinal (visceral) fat mass, We offer our thanks to A. R Leif, CD.
and often account for most ofthe variation in Olavv/sky, D. G. Cook, R Grissom, and R N.
J.
total body-fat content. Our studywas designed Gray for field assistance. E. G. Bolen, L. D.
to develop models using explanatoiy variables Vangilder, D. H. fohnson, and C. B. Ramsey
that could be applied to live as well as dead provided comments on the manuscript. The
pintails. project was supported by the Caesar Kleberg
Miller (1989) developed regression models Foundation for WildHfe Consen'ation and the
to predict carcass fat on live pintails from Sac- Texas State Line Item for Noxious Brush and
ramento Vallev, California, but cautioned WeedControl.Thisismanu,scriptT-9-488ofthe
againsttheiruseoutsidethatregion.Ourregres- College of Agricultin-al Sciences, Texas Tech
sion models forcarcass fatprovidedbetteresti- Universitv'.
matesoffat(K"> .71)forlivepintailsthanthose
developed forCaliforniabirds IR'< .66). How- LiTER.\TURE Cited
ever, similarto Millers (1989) studv, bodvmass
alone accounted formostofthevariation (R' > Baii.kv, R. O. 1979. Methodsofestiniatiujj;total lipidcon-
.69) in pintail carcass fat. tfiitinthe RedheadDuck(Aythi/ti(nucrianui)andan
The possibility of a condition bias among ex'aluation ofcondition indices. Canadian lonrnal of
Zoologv57: LS3()-LS33.
water-fowl captm-ed in baited traps versus the Bii.LHosE, F. C. 19(S0. Ducks, geese tuid swans ofNorth
general population has been addressed America. 3rded. Stac^iole Books, Harrisburg, Penn-
(Weatherhead and Ankney 1984, 1985, SN'Kania.
Buniham and Nichols 1985). Hypothetically, Bolen, E. C, L. M. Smith, and II. L. Schhamm 19S9.
Plava lakes: prairie wetlands of the Southern High
birds in poor condition may be hungrier, less Plains. BioScience39:6L5-623.
wary, and more likelyto enteratrapcontiiining BuRNUAM, K. p., andJ. D. Nichols. 1985. On eoncbtion
food.Condition modelscouldbeusedtotestfor biasandliand-recoxcn-datafromlarge-scalewaterfowl
evidence of a body-condition bias, given that bantling programs. Wildlife Societv Bulletin 13: 345-
:349.
samplesofpintailscapturedboth inbaitedtraps CiiAPl'KLL. W. A,, and R. D. Titman 1983. EsHmating
and bv presumably less-biased methods (e.g., reser\'e lipids in Greater Scaup (Aijthijd iiwiihi) and
net gun) are available. Lesser Scaup (Ai/thi/a affiuis). C'anadian |onrnal oi
Zoologv61:3.5-38.
Models could be u.sed to test for annual Flickincek, E. L., and E. G. Bolen. 1979. Weights of
variation in bodv condition and for chans;es in LesserSnowGeesetakenontheirwinterrange.Jour-
condition across the winter. Ringelman and nalofWildlife Management43:,531-533.
Szymczak (1985) demonstratedthepotential of Folk C., K. Hudec. andJ.TOUFAH 1966.Theweightof
the Mallard {Anas plati/rlnjiichos) and its changes in
condition indices in determining spatial differ- thecourseofthe\earZoologx List\ 15: 249-260.
encesin bodycondition and thepreferabilitvof Hanson 11. C. 1962.Thedviiamicsofconditionfactorsin
condition indices to use of body mass alone. Canada (ieese and their relation to seasonal stresses.
Heppetal. (1986)alsousedcondition indic-esto Arctic Institute North .America Technical Paper No.
12. Fairbanks,Alaska.
docmnent a po.sitive relationship betAxcen con- ilMKds D. A., ;uid L. M. Snutii 1992. Ecolog\-ofplava
dition andsunival in mallards. lakes.In:Waterfowlmanagementhandbook.LI.S.Fish
susheofTuuhlled.tsboeewapvtieenrtriaffiiolewdlcwobnihdoeilontgiiousnstse.dmoHodouewtlseisvcekr^sh,tohmueolddeeelbose- ill ITaaannnt(dti;.nW|n.iRm.lD,-d.lbRia.fNneiJd.cSeedhBrlo\Moliaicslielma.Lr1ed9asR8f.6l;.euFitPdh1iRy3tess.3iyr.oen7ll.ooagtliidcoansslhiJc.pontFcohhtHuiinontneisno.gf
1992] PiN'IAII,CoxniTIOX MODKLS 231
\iilii('ral)ilit\. |()iinialol\\ildlifcMaiia<4ciiH'iit30: 177- i-ouditioii of .\ortlu-rn Pintails in the Soulheru High
].S3. Plains.JonrnalofWildlife Management57. Inpress.
1\KHSON. C.C;., and P. A. N'oiis, |ii. 19S2. Kstimatiii'^ lipid Sii!i:i;t. M. 1975.Seasonalchangesinthediet,bodvweight
contentoi Sandliill (francs Ironi anatomical nicasurc- andconditionoffledged Mallardsineastern Enghuul.
nicnts.Jonrnalof Wildlife Management46:478—48.). International(>ongre.ssofCameBiologists7:339-347.
JOHN|SoOiiNlM;1).1I9I8..5.(;..\iL\.eK\haalin'aIti()Kn,oJ.fHckoinndiktcikokn,iandnidce1s).fCo.r TiioM.PArSe.di\c'.ti(n;.g, fSa.tKc.onMt.eMnNtCUoYf,geaensdeJ.frPo.mPhakb.\doi-m.TiTn.a1l98f3a.t
birds. |onrnalof \\ildlifc.Management49:569-.575. weight, journal of Wildlife Management 47: 1115-
Miil.KK. M. H. 1989. Estimatingcarca.ssfatandprotein in 1119.
jXooufrtnlailenoilWiPlidntlaiifl'.es Mdaunrianggemtelinetn5o3:nh1r2e3e-d1i2n9g. season, \\i:\riii:niii;\i) P. J., andC:. I). Ankni-:v. 1984. A critical
OuKN. .\I., and W. A. Cook 1977. N'aiiations in hocK assiunption of band-reco\en models mav often be
weight, wing lengtli and condition ofMilliards (Aims \iolated. WildlifeSocietyBulletin 12: 198-199.
pl(itijrlujncli()s)im(]tlic-irrelationsliiptoen\iromneutal . 1985. (Condition bias and band recoven data: a
changes.JournalofZoologN'183:377-395. repK toBnrnhamanil\ichols.WildlifeSocietv Bulle-
HwEi.lNC. D. G. 1979.Tlieannua!cvcleofhodvcomposi- tin 13:349-351.
tionofCanadaGeesewitlispecialreferencetocontrol \\iivri: R. J.,and E. C. Boi.KN. 1984. \ariation inwinter
ofreproduction. .\nk96: 234-252. tatde-potsandconditionindicesofMallards. |onrTialof
Hi\(:i:i \i\N ]. K.. and M. R. Szymcz.ak. 1985. A ph\-.sio- Wildlife Management48: 1370-1373.
logicalconditionindexforwinteringMallards, [ournal WisiiAHf. R. A, 1979. Indicesof.structuralsizeandcondi-
ofWildlifeManagement49:564-.568. tionof.AmericanWigeon(Aimsaiiwricaiia).Canadian
S.AS IN-STITLTE. I\C 1985. SAS user's guide: statistics. JonrnalofZoolog\-57:2369-2374.
Version 5 edition. SAS Institute. Inc.. Can. North Wooii.M,!., R F. 1978. Omental fat: acondition index for
Carolina. Red-billedTeal, [onmal of\\'ildlife Management42:
SmitahndC.PW..D,.F.KAk.vJwoohondson199|1..B.TrBeonkdtsxeirn.chJi.cPk.Bblr,e\eddii;nn.g 18.8-190.
populations. U.S. Fish and Wildlife Senice
.Administrati\e Report. Laurel, Mar\'land. Received 1 fuiic /.9.9/
SNirrii. F. M.. and D. G. SllKKl.KV. 1993.' Factors affectine AreepU-d22'}\nie IW2