Ornithological Monographs 18

60 2 0
  • Loading ...
1/60 trang

Thông tin tài liệu

Ngày đăng: 04/11/2018, 17:19

BREEDING BEHAVIOR BIOLOGY OF THE AND OLDSQUAW (CLANG ULA t-]YEAdrALIS L ) BY ROBERT ORNITHOLOGICAL M ALISON MONOGRAPHS PUBLISHED THE AMERICAN BY ORNITHOLOGISTS' 1975 NO UNION 18 BREEDING BIOLOGY AND BEHAVIOR OF THE OLDSQUAW (CLANG {_/L•I HYœA4t•ILIS L ) BY ROBERT ORNITHOLOGICAL M ALISON MONOGRAPHS PUBLISHED THE AMERICAN BY ORNITHOLOGISTS' 1975 NO UNION 18 ORNITHOLOGICAL MONOGRAPHS This series,publishedby the AmericanOrnithologists' Union, has been established for major paperstoo long for inclusionin the Union'sjournal, The Auk Publication hasbeenmadepossible throughthe generosity of Mrs CarllTuckerandtheMarciaBradyTuckerFoundation,Inc Correspondence concerning manuscripts for publicationin the seriesshould be addressed to the Editor,Dr JohnWilliamHardy, Departmentof Natural Sciences,The Florida State Museum, University of Florida, Gainesville, Florida 32611 Copiesof OrnithologicalMonographsmay be orderedfrom the Assistant Treasurerof theAOU, GlenE Woolfenden,Departmentof Biology,University of SouthFlorida,Tampa, Florida 33620 OrnithologicalMonographs,No 18, vi + 52 pp Editor-in-chief: John William Hardy SpecialAssociateEditor for this issue: Milton W Weller Author's address: Wildlife Branch, Ministry of Natural Resources,Whitney Block, Queen's Park, Toronto, Ontario Issued: September23, 1975 Price: $3.50 prepaid ($2.50 to AOU Members) Library of CongressCatalogue Card Number 75-20649 Printed by the Allen Press,Inc., Lawrence, Kansas66044 Copyright @ by American Ornithologists' Union, 1975 TABLE TABLE of CONTENTS INTRODUCTION MATERIALS OF CONTENTS AND METHODS iii 1 The Study Area Weather During the Study Period Vegetationin the Study Area Census Methods Territorial Winter RESULTS Behavior Behavior Population Characteristics 8 Homing 10 Nesting 11 The Eggs 16 The Nest and Incubation 17 The Young 23 Territoriality 24 Displays 32 Other Aspectsof ReproductiveBiology 43 Major FactorsInfluencingProduction 46 ACKNOWLEDGMENTS SUMMARY LITERATURE CITED iii 48 48 50 LIST OF FIGURES Figure Location of study area 2 Map of studyareashowingtraditionalnestinglocations 3 Habitat of the study area 4 Head plumagesof Oldsquaws "Hummock"habitatin early June suitablefor nesting Oldsquawnestcup Variationin headplumages of downyyoungOldsquaws 23 Plumagedevelopmentin youngOldsquaws 25 Plumagedevelopment in youngOldsquaws 26 14 10 Fall and winter plumagesof immature Oldsquaws 27 11 Fall and winter plumagesof adult Oldsquaws 28 12 Characteristic posturesof maleOldsquaws 33 13 Adult male OldsquawsperformingBreastDisplay 35 LIST Table OF TABLES Historiesof bandedOldsquawsat Churchill,Manitoba 11 Locationsof Oldsquawnestsin the studyarea, 1968 to 1971 12 Concealmentrankingfor Oldsquawnestsin the study area Data from nestsof previousyears is also presentfor comparison 13 Distancesbetween Oldsquaw nests and the nearest open water 15 Nest associationbetweenOldsquawsand Arctic Terns in the study area Only active nestsof known historyare included 15 Clutchsizesof Oldsquawsin the studyarea, 1968 to 1971 17 Avian and mammalianpredatorsand nestdestruction in the studyarea 19 Oldsquawnestlossesdueto predationin the studyarea 20 Summaryof the fate of Oldsquawnestsin the study area, 1968 to 1971 21 10 Hatchingdatesof Oldsquaws in the studyarea, 1968 to 1971 22 11 Responses of drake Oldsquawsto stuffeddecoysand recorded vocalizations 29 12 The orderof displaysperformedby courtingmales 37 INTRODUCTION The Oldsquaw (Clangulahyemalis),or Long-tailed Duck, is probably more numerousand widespread than any other speciesof arctic waterfowl (Delacour1959) It breedsacrossnorthernEurasiaandfrom PointBarrow, Alaska,alongtheArcticcoastof NorthAmerica, including thewestern coasts of HudsonandJamesBaysandin northeast Labrador(Godfrey1966) Breedingindividualshave been found on almost all the Arctic islands of Canadato a latitudeof 83ø north, and the speciesreportedlybreedson Baffinand Southampton Islands(Phillips1925) Althoughthe Oldsquaw hasbredalongthe eastcoastof Labradorand in the Gulf of St Lawrence, thereis no evidence that it breedstherenow The bird is circumpolar in distribution andcommonly breedsin Greenland(to 83ø 23' N), Iceland,the Faroes,the north coastsof Norway,Sweden,Finland,Russia,on the New Siberian Islands andall alongthecoastof theArcticOceanto theBeringSea (Millais 1913) The winterrangeof the species is well known(Millais 1913, Bent 1925, Phillips1925) However,winteringareasof specificnorthernpopulations are unknown,primarilybecause of the lack of bandingdata A largeproportionof the Icelandpopulationapparently wintersin southwest Greenland (Salomonsen 1950) whilesomeindividuals of certainRussianpopulations winteron the westcoastof Europe(Boyd 1957) The breeding biologyof the Oldsquaw is poorlyknown.Drury (1961) mentioned certaindisplaysthat he saw on the breedinggrounds.Millais ( 1913), Bent( 1925), andPhillips( 1925) described nestlocation,clutchsize and aspects of adultbehavior,but no studiesof individuallyrecognizable breedingOldsquawshave been published Themainobjectives of myresearch reported in thispaperwereto determine: (1) Oldsquawpopulationlevelsand breedingpair distribution, (2) nest site tenacity and homing, (3) nestdistributionand location,nestingsuccess, and the effectof weather upon nesting and renesting, (4) territorial behavior, and (5) to describespecies-specific displaysof this speciesin sufficientdetail to permitcomparison with thoseof otherspecies MATERIALS THE AND METHODS STUDY AREA Thispapercontains the resultsof studiesof Oldsquaws conducted in four consecutive breedingseasons,1968 to 1971, at Churchill,Manitoba (58 ø 45' N, 99ø 5' W) I observedOldsquaws on a 400.0ha area about5 km east ORNITHOLOGICAL HUDSON 59 ø 05' •urchill NO MONOGRAPHS 18 BAY STUDY AREA 58 ø •) Churchill Stygge 45' Lake Churchill 58 ø River 25' • 5000 5000 58ø 05' METERS 94ø 15' 93 ø 55' Figure1 Map showing locationof the studyarea ofChurchill (Fig.1) TheOldsquaw breeding population in thisareaaverages 45 pairs,themajorityarriving in thefirstweekof June.Pairsaremost commonly observed onsmallinlandponds butindividuals andsmallgroups mayoccasionally be seenamong thechunks of packice in openwateron HudsonBay, especially at the mouthsof rivers Thestudy areaisabout14kmeastofthemouth of theChurchill Riveron thewestcoast ofHudson Bayandiscontained within58ø43'N to 58ø46'N and93ø 52' W to 94ø 01' W (Fig 2) The areaincludes sparsely forested tundra,dry upland,marshland andscrubland, andextends almost10 km along theHudson Baycoast.JehlandSmith(1970) described theareain detail.Thereare90 pondsandlakesranging in areafrom0.1 to about 20.3ha andaveraging 2.8 Noneof thesepondsandlakeswasreduced tomud-flatconditions duringthestudy.Mostof thesmaller pondsareice-free by10June, andallthelarger ponds andlakes(except Stygge Lake)areclear of iceby 20 June.Remnant icemayoccuralongthecoastof Hudson Bay until late July Oldsquaws consistently outnumber allother species ofwaterfowl inthestudy area.However, theCommon Eider(Somateria mollissima) andtheCanada 1975 ALISON: OLDSQUAW BIOLOGY 94ø 00' I 93ø 53' I I I • I I I I HUDSON BAY L Figure Map of the study area showing traditional nesting location Minimum densitiesof one nest per 2.3 areas are shaded Goose (Branta canadensis)are quite common The following speciesalso occurmoreor lessregularly: GreaterScaup(Aythya marila), Green-winged Teal ( Anas carolinensis ), Pintail ( Anas acuta), American Widgeon ( A nas americana), Red-breastedMerganser (Mergus serrator), Mallard (Anas platyrhynchos) and Common Scoter (Melanitta nigra) In orderthat breedinggrounddata couldbe supplemented by observations of winter behavior,Oldsquawswere observedduring the winters of 1967 to 1969 at Toronto Harbor, Ontario (43 ø 40' N, 79 ø 30' W) The average winteringpopulationof this speciesat Torontocomprises about7,000 individuals In addition,observationsof the behavior of six captive Oldsquaws supplemented field data WEATHER DURING THE STUDY PERIOD In 1968, daily temperaturesin the last 10 days of May were 3.$øC above normal (-2.1 øC), whereasJunetemperatures were $.1øC and 1.9øC, respectively,below normal (6.1 øC) Most pondswere not clear of ice until 20' June that year In 1970, temperatures in the final week of May averaged2.2øC abovenormal, June temperaturesaveraged3.0øC abovenormal, and ponds were clear of ice by June Juneprecipitationfrom 1968 through1970 wasbelownormal ($1.4 ram), but in 1971, abovenormal rainfall was recordedfor that month Wind velocities throughoutthe study period averaged21 kmph and the mean daily ORNITHOLOGICAL MONOGRAPHS NO 18 Figure Habilat typical of the study area showingBlack Spruceand open tundra association maximumwind velocitywas 38.8 kmph In general,the 1968 breeding period at Churchillwas dry and moderate,the 1969 seasonwas dry and cold, the 1970 periodwas dry and warm, and the 1971 seasonwas wet and cold VEGETATION IN THE STUDY AREA Despite an overall impressionof monotonoussamencss(Fig 3), the vegetationin the studyareavariedconsiderablylocally On the basisof component plant types, it was possibleto subdividethe study area into the following categories: tundra, marsh,dry upland and scrubland (a) Tumlra. Tundra includes those typically grassy expanseslying beyondand occasionallywithin the limit of rank forest The study area is mainly tundra and containsextensivelowland areas dominated by sedges includingHudsonBay Sedge(Carex amplyorhyncha)andNorthernBogSedge (C gynocrates) Grasses(Poa spp.) and dwarf willows (Salix spp.) commonlyoccur.Frequentlybryophytes andlichenspredominate, thewholeforming a continuous growthtypicallylessthan 35 cm in height Isolateddwarf birches (Betula spp.) may occasionallyoccur (b) Marsh. As a result of the relatively poor drainage large expanses of shallow surfacewater generallyoccur In such marshlandareas, the dom- 40 ORNITHOLOGICAL MONOGRAPHS NO 18 in aggregations of birdsmembers of pairswerenot alwaysthosebirdsclosest together.Both membersof a pair attemptedto drive away any intruding drake that approachedtoo closely,but intrudingducks were generally ignored Pairedbirdsrarelydisplayed to oneanotherexceptin copulationsituations Wheneverthe birds becomeseparated,the drake alwayssearchedout the duck In such circumstances, the drake assumedS postureswhich were maintaineduntil the femalewas located The durationof the pair bond is unknown While most birds were paired by the beginningof March, others were still courtingvigorouslyin mid-April Once formed, the pair-bond appearedquite strongin this species.Reportedly,if the drake is killed the duck will remain by his sidefor severalminutes(MacKay 1892) and in my experiencethe converseis true for the drake Such behavior has not been reportedin other speciesof waterfowl Displaysassociatedwith copulation. Copulationwas observedon six occasions.Thesewereon April, 29 April and May 1968, and on 12 and 13 Februaryand 23 April 1969 Exceptfor the first instance,both pre- and post-copulatory behaviorwas seen Copulationor attemptedcopulationbetween immatures and adults or between immatures was not observed No instancesof attemptedrape were noted The only previousreportsof copulationin the Oldsquaware threeexamples by Myres (1959) and one by Drury (1961) Myres reportedthat prior to copulationthe duck invariablyassumeda prone posture,but that no other particularpre- or postbcopulatory displayswere noted Copulationusually occurredafter the pair moved away from the main flock Copulationwas neitherconfinedto any particulartime of day nor to any specialcircumstances.In most instancesthere was little indicationthat copulationwas about to occur until the female began Soliciting Prebcopulatory behaviorcomprisedcourtshipdisplaysincludingBt, LHs, P, BD and Ns and Bt and/or LHs were pre-copulatorydisplaysin all instancesof copulationnoted Ns was less commonand occurredin three instances.The numberof pre-copulatory displaysperformedby individual maleson one occasionrangedfrom one to ten Femalepre-copulatory displaysincludedC1, Hu, LHs, P, Ns and Soliciting Of these,Ns (4 instances)and C1 (3 instances)were the mostcommon LHS, a commondrake pre-copulatorydisplay, was observedon only one occasion.The female of a pair never initiated the pre-copulatoryactivities but appeared to be respondingto the drake's movements In all five sequences observed,the femaleperformedat leastone pre-copulatorydisplay andthemaximumnumberof displaysperformedwas9 Copulationoccurredon water and in each instancethe drake graspedthe 1975 ALISON: OLDSQUAW BIOLOGY 41 nape feathersof the female while mounting As the drake mountedthe femalewasinvariablyforcedunder,only the headremainingabovewater On three occasions violenttail shakingaccompanied the apparentintromission Intromissionis reportedlyrather prolonged,occasionally lastingas long as one minute (Myres 1959) No specialmale post-copulatory displayswere recorded,but post-copulatory behavioralwaysincludedcourtshipdisplays.BT wasperformedin two instancesas were Ns and the sequenceP + LHs + Wf LHs (not as part of a sequence),S, and BH wereeachobservedonceonly Drakesperformed from oneto four post-copulatory displays P wasthe mostcommonfemalepost-copulatory displayand was performed on two occasionswhereasLHs was observedonly once Ducks performed from one to five post-copulatory displaysin any giveninstance Discussionof displays.-•Displaysin waterfowl are derivedfrom comfort movementsand "intention" movementsthat have subsequentlybecome ritualized(Johnsgard1968) Many displaysthat are clearly derivedfrom comfortmovementsseemirrelevantwhen performedas courtship.Porpoising is usedby malesin courtshipand pre-copulatorydisplayand by femalesin pre-copulatoryandpost-copulatory display Body-shaking hasbecomea male courtshipdisplay and occasionallyoccursin male post-copulatoryactivity (followingporpoising) Many avian displaysapparentlyhave evolvedfrom behaviorin conflictsituationswhere a bird is simultaneously stimulatedto behavein incompatibleways Courtingmalessexuallyattractedby females may be driven simultaneously to attack or escapefrom other males or females Females sexually attracted to males may be driven to attack or escape from males and females In female Oldsquaws Chin-lifting (or Inciting) probably representssimultaneousaggressionand appeasement toward the drake and occursin pre-copulatorydisplay and in responseto male courtship SimilarlyHunch seeminglyrepresentsconflictingstimuli of aggressionand appeasement.The back and scapularfeathers are ruffled and the tail is elevated and slightly spread (aggression)while the head is withdrawninto the shoulders(appeasementgesture) This displayis given by femalesin responseto male courtshipand as pre-copulatoryand postcopulatorybehavior Bill-dippingis anotherdisplaythat could result from the simultaneous tendenciesto attack and appease.Conceivablya paired bird couldbe simultaneously motivatedto attackand appeasea nearbymate More likely though,an unpairedbird upon encounteringanotherindividual might be variouslymotivatedto attack or escapeor appease.Bill-dipping is more commonlyperformedby paired birds than by unpairedbirds It is generally acceptedthat the perceptionof certain external stimuli presentedby one animal can increasethe probabilitythat that animal will 42 ORNITHOLOGICAL MONOGRAPHS NO 18 be attackedby another These stimuli may include aggressivegestures, specificcolor patterns,and body markings(Tinbergen1959) Thus hiding certainattack-eliciting patternscan lower the probabilitythat an animalwill sustainan attack The black, pink-bandedbill of the male Oldsquaw is similarlythrustforwardin attack Turning-the-back-of-the-head, a courtship pre- and post-copulatorydisplaythat hides the bill from anotherindividual probably has appeasementfunction Visual alarm signalsin most speciesof waterfowl include an alert posture with head held high McKinney (1961) concludesthat the Head-turn displayof some eidersevolvedfrom the habit of looking back alternately with one eyethenthe other towardsomeapproaching threatsource.Similar side-to-side headmovementscouldresultin Lateral Head-shaking,a common male Oldsquawdisplay Alternatively,Lateral Head-shakingcould be an apparentlyirrelevantdisplacementFlicking-water-off-the-billresultingfrom simultaneous attackand escapestimuli Lateral Head-shakingis performedby courtingmalesand as pre- and post-copulatory behavior Rear End Display, unique amongwaterfowl,was probably derivedfrom two separatemovements The bowing forward of the head may be a modified Bill-dippingmotion The subsequent lifting of the posteriorpart of the body verticallyout of the water suggests movementsperformedby both sexesimmediatelyprior to diving The lifting of the tail may have evolved as a modificationof the divingmovement McKinney (1961) has concludedthat severalvisible displaysof eiders have apparentlyevolvedto facilitate thosevocalizationsaccomplished by a complex contortion of certain tracheal structures During the Head-throw displayof CommonGolden-eyes(Bucephalaclangula)the tracheais momentarily extendedand then returnsto normalposition(Johnsgard1968) This extensionapparentlyaids the productionof the most commonvocalization of that species.Bill-tossingof adult male Oldsquaws,a displayin which the tracheais similarly extendedmomentarily,may be related functionally to the complex"ahr-ahr-ahroulit"vocalization In the Oldsquaw,morphology andbehaviorensurethat immaturebirdsdo not pair Adult plumageis not attained until the secondwinter (Phillips 1925) Immature malesdo not possessany of the distinctiveplumagepatterns of adult males Whereasmost immature males by May are capable of performingall the visibledisplaysof adult males,they not produce the corresponding audibledisplaysof adults Bill-tossing performedby immaturemalesis accompanied by distorted"ahr-ahr-ahroulit"vocalizations Immature males performingRear End Display not produce any accompanyingvocalization Sonograms of Oldsquawvocalizationsshowthat most calls rangebetween 1975 ALISON: OLDSQUAW BIOLOGY 43 0.4 and 1.4 secondsin duration Five renditionsof the "ahroulit" portion of the "ahr-ahr-ahroulit" vocalization showa highdegreeof individualvariation A similarindividualvariationwas visiblein audiospectrograms of all other vocalizations.Marler (1960) has suggested that detailedchangesin pitchcanexpress individualityamongseveralrenditionsof the samespeciesspecificvocalization.Individualvariationin bird songoccursin Chipping Sparrows(Spizellapasserina)(Marler and Isaac 1960) that have only one song,as well as in Mistle Thrushes(Turdus viscivorus)(Isaac and Marler 1963) that have large repertoiresof vocalizations.Borror (1961 ) has concludedthat two individualsseldomproduceidenticalsongs As Oldsquaws are nocturnalmigrantsvoicecommunication betweenpairedbirds probably lowersthe possibilityof them becomingseparatedfrom each other during spring migration Mutual vocal recognitionwas consistentlydemonstrated by a pair of captiveadultOldsquaws that constantly communicated with each other nightly throughoutthe spring of 1969 Yet nocturnalvocalizations emittedby anotherunpairedadult drake evokedno responsefrom the paired duck OTHER ASPECTS OF REPRODUCTIVE BIOLOGY Number of adults forming pairs.•Photographs of flocks of Oldsquaws takentwice weeklythroughoutthe winter of 1968-69 facilitateddetermination of sex ratios Adult males comprised11.4% of all Oldsquawscounted in November and December whereas adult females represented29.4% In January the proportion of adult males increasedsignificantly(t = 4.23, df=9 P•< 0.01) and comprised31.4% of the winter populationof the species,comparedto the adult female proportion of 39.8% The January populationof adult femaleswas not significantlygreater (t = 1.86, df = P •< 0.05) than the Decemberpopulation Thesedata seeminglysupportthe suggestionby Phillips (1925) that adult males migrate to the wintering groundslater than adult femalesand immaturesof both sexes No further changein the relative proportionof the sexesoccurred By 15 February at least 22% of all Oldsquawswere paired, representing 35% and 29% of all adult males and females, respectively By 16 March 34% of the populationwas paired (57% and 46% of the adult males and females, respectively) By 30 April 73% of the adult males were paired with 57% of the adult females(44% of the total population) Endurance of pair bonds. Unlike most other ducks Oldsquaws possibly pair for more than one breedingseason(captive pairs reform each year) On the study area one pair of Oldsquawswas capturedon the same lake in two consecutive years There doesnot appearto be any reasonwhy pairs could not reform in consecutiveyears, and other reformed pairs may 44 ORNITHOLOGICAL MONOGRAPHS NO 18 have been presentbut remained undetected(i.e the drakes had not been bandedin previousyears) In this species considerable flock shufflingprobably occursduring the fall migration Yet at least two adult Oldsquaws (one drake) capturedand bandedat Toronto, Ontario, were recapturedin a subsequent year at the same location (i.e at the exact site as before) and both passedthe entire winter of 1970-71 in the Toronto area On the basis of feeding behavior, plumage characteristics, and vocalizationpeculiarities,I suspectthat at leastthreeadditionaldrakesreturnedto the same siteto feed daily throughoutthe winterof 1969-70 and 1970-71 (the feeding locationmade capturefor bandingimpossible) It thus appearsreasonable to assumethat at leastsomeOldsquawswinter in the samegeneralarea, if not at the sameloactionin consecutiveyears If so it is highly likely that pairs could reform year after year even if the membersof the potentialpair migrate separatelyeach fall, as long as both winter at the same location in consecutiveyears Only two of over100 adultdrakeOldsquaws bandedin the studyareawere subsequently recaptured,althoughoneof thesewasrecoveredin threeconsec- utive yearsat the samepond Very few adult drakeswere banded,and it appearsprobablethat had a detailedstudyof bandeddrakesbeenconducted, a largernumberof bandedindividualswouldhavebeenrecoveredin subsequent years If someadult drakesdo home and if pair-formationdoes occur on the wintering grounds,then in every instancewhen a drake returns to a specificpond he must be paired with the sameindividualas in the previous year (assumingthat drakes follow their mates from the wintering grounds to the breedingponds) Thesecircumstances would resultin the emergence of a localizedbreedingpopulation.At leastsomedrakesdo not alwaysreturn in subsequent yearsto pondsusedpreviously Two drakesbandedas adults at Yamal Peninsulain northern Siberia (72 ø N, 72 ø E) in August 1933 and 1934, respectively,were recovered,one in Norway in July 1938, and the otherin Swedenin June 1935 (Boyd 1957) Fidelity to nest site.-•Some adult females return to the exact nest site occupiedin a previousyear However, it must not be inferred that this phenomenonoccursonly in thoseinstancesin which nestswere successful Hilden (1965) suggeststhat nest site fidelity occurs more likely in the absenceof predation or other disturbance The three femalesthat returned to an exactnestsite usedpreviouslyhad had successful nestsin the previous year One femalenestedon the samesmall islandoccupiedthe previousyear eventhoughthe nesthad beendestroyedin the formeryear Anotherfemale, whose unsuccessfulnest was located on an island, nested on the mainland at the same pond in the next year Successor failure of a previous nest clearly doesnot determinethe nestsite chosenin any givenbreedingseason 1975 ALISON: OLDSQUAW BIOLOGY 45 It is probablyadvantageous for birds to breed in localitieswith which they are familiar (Lack 1954) Nest locations. Evans (1970) noted nest associationsbetween Oldsquawsand Arctic Terns at Churchill,but his sampleof Oldsquawnestswas not random In this study, among island-nestingOldsquaws,a significant association betweenthe two specieswas observed,but on the mainlanda significantdisassociation occurred.Koskimies(1957) suggested that Oldsquawsactivelyselecttern coloniesin which to nest as a resultof imprinting (i.e ducklingsimprintedto nearbyterns in the nest vicinity) Oldsquaws in my studyhave invariablycompletedor partially completedtheir clutches prior to the arrival of ternson the breedinggrounds,and in most instances Oldsquawclutcheswere completebefore terns initiated nesting Inasmuch as Oldsquawsnestedprior to tern arrival in most instances,it is unlikely that they chosenest siteson the basisof visualor auditoryrecognitionof terns Oldsquawnestswere frequentlylocatedat traditionallocations Only of 79 islandslocatedin the studyarea had Oldsquawcoloniesin each year of the study; 11 had nestsin at leastone year, 16 had nestcupsof previous yearsand 45 had no evidenceof previousoccupationby Oldsquaws.Evans (1970) notedconcentrations of nestcupsof this specieson certainislands containingtern coloniesand suggestedthat once a particular female Oldsquawbecameestablished near a colonyof terns,she might return in subsequentyears regardlessof the presenceof terns He noted many instancesin which there were femalesnestingin tern coloniesin one year, whereasin the next year thesesameindividualsnestedin locationswith no terns nearby Converselysome femalesthat had nested at ponds where terns were not residentnestedin subsequentyears on islandscontaining tern nests Hence it is doubtfulthat female Oldsquawscan becomeestablished,perpetualtern-colonynesters Oldsquawnest loss by predation on islandswith nestingArctic Terns wasnot significantly greaterthan withoutthe terns The positiveassociation betweennestingOldsquawsand nestingArctic Terns is not a relationship significantly beneficialto Oldsquaws.In 1971, an entire islandcolonyof Oldsquawnestswas destroyed by two ParasiticJaegers,althoughtwo pairs of Arctic Terns nestedon the same island (the tern nestswere also destroyed) On two occasionsI observedthe jaegerswalking about on this island,and althoughthe ternsswoopedfrequentlytowardthe predators,the latter seemedundisturbed.Possiblysome Oldsquawsmight derive benefit from nestingin large coloniesof Arctic Terns, but the observedpositive nestingassociation betweenthe two speciesis probablya resultof similar habitat preferences, specificallyoverlappingnest site requirements 46 ORNITHOLOGICAL MA$OR MONOGRAPHS FACTORS INFLUENCING NO 18 PRODUCTION l•eather. Inclement weather and cool temperaturesusuallydelay laying in waterfowl Sowls (1955) observedthat Mallards and Pintails delayed egg laying by as much as two weeks in years when 15 April to 30 May mean temperatureswere below normal Low (1945) noted that Redheads nestedsubsequent to the first warm weather in April or early May At Churchill, 1969 May temperatureswere unusuallycold, and in that year Oldsquawsdelayednestingby about 10 days Cooch (1965) reportedthat during inclement weather Common Eiders almost ceased egg laying Interruptedegglaying alsooccursin many other speciesof Arctic waterfowl, but it is not alwaysregulatedsolelyby inclementweather No instancesof interruptedegg laying were observedin Oldsquawsin this study I have suggested that a minimumpossiblebreedingperiod is availableto Oldsquawsat Churchill In 1969 when nestingwas delayed,breedingponds remainedunfrozenlater than normal Had thesepondsfrozen over earlier, late hatchingOldsquawsmight not have survived In most years it would be difficultfor this speciesto delaylayingand yet successfully rear a brood Renestingdoesnot occur in Oldsquaws.Yet in the one cold year of this studyfewereggshatchedfrom each clutch,and the resultingsmallerbroods seemedto be more efficientlybrooded The effect of local weather conditions on incubated clutches in waterfowl is not well documented.Gollop (1954) reported that cold weather and snowin May did not adverselyaffect Mallard productionin Saskatchewan, but Cooch (1965) found that adverseweather conditionscould produce fluctuationsin the magnitudeof egg loss in Common Eiders Miller and Collins (1954) observedthat excessiverainfall was an important causeof egglossin Redheads,but snow,heavyrainfall or low temperaturesdid not adverselyaffectnestingsuccess in severalspeciesof prairie waterfowl (Keith 1961) In the presentstudyit was similarly found that inclementweather did not significantlyaffect egg loss (although severelycold temperatures did not occur) This observationpossiblycorrelateswith the fact that Oldsquawsbreedingat Chumhillcomprisea more or lessisolated,stablepopulation seeminglyadaptedto local conditions(includinglimited weather fluctuations) Predation. Most recent studieshave demonstratedthat nest predation is the chief causeof egg loss in waterfowl Similarly in Oldsquawsof this studypredationwas the main factor contributingtowardsunsuccessful nests Nestswere frequentlydestroyedin traditionallocationswhereasnestslocated nearby were successful.In the study period one colony was completely destroyedannually, but another situated5 km northeastof the first was never molested Almost invariably colonialpredationwas causedby avian 1975 ALISON: OLDSQUAW BIOLOGY 47 predators, andthusit mightbe concluded thatcertainavianpredators hunted moreintensively in traditionalareas It is not knownwhetherindividual avian predatorsreturned to the study area annually Nest predationdid not appearto be strictlyregulatedby the degreeof nestconcealment Relativelyexposed nests(in dry upland)werefrequently destroyed and well concealed nests(in marshland)wererarely destroyed An inconsistently large proportionof apparentlytotally concealednests (thoselocatedbeneath dwarfsprucetrees)werelostto predators, specifically to ParasiticJaegers.On two occasions I observedtwo ParasiticJaegers land on largeislandscontaining Oldsquawnests,and in both instances the birds systematically approached everysprucetree growingon each island In everycasethey walkedaroundeachtree severaltimesand occasionally movedto lowerboughs, apparently searching for nests.Frequently, especially on islands,nestslocatedundersprucetreeswere destroyed beforethoselocatedat othersites Possiblyjaegersnot only searchtraditionalareasbut alsoexamine, perhaps morecarefully, certainpotentialnestsites(i.e beneath the few sprucetreeson islands).It wouldobviously be impractical for these birdsto searchbeneaththe thousands of smallsprucetreeson the mainland asonlya slightproportion of theseconcealnests.Hence,the disproportionately high rate of destruction of seeminglywell concealedOldsquawnests (on islands)mightresultfrom specificfeedingbehaviorof ParasiticJaegers About58.9%.of all Oldsquaw nestsweresuccessful in this study.Keith (1961) summarizedrecentstudiesof hatchingsuccessin waterfowl (involvingover 3,500 nests)and reportedthat 56% of "diver" (presumably Aytha spp.) nestswere successful as comparedto 39% for dabblers(Anas spp.) In his own studythe sameauthorreportedthat 31% of scaupnests hatchedsuccessfully Lokemoen(1966) noted a hatchingsuccess of only 10.2% in Redheadeggsin Montana The figurewas furtherreduced(to 9.9%) whenRedheadeggslaid in nestsof otherspecieswere not included in the data The mostimportantcauseof egglossin Redheads wasdesertion (Lokemoen 1966) but predationalso accountedfor a large percentage Althoughfloodingmay be an importantcauseof egglossin certainspecies of divingwaterfowl,no instances of floodedOldsquawnestswereobserved in this study Egg loss due to predation appearsto be greater for scaup and possiblyRedheadsthan for Oldsquaws.The StripedSkunk (Mephitis mephitis)is an efficientdestroyerof scaupand Redheadnestsand accounts for the majorityof eggslostby thosespecies(Keith 1961, Lokemoen1966) The ParasiticJaeger,the major destroyerof Oldsquaweggs,may not be as proficientas the StripedSkunk in locatingnests,especiallymainlandnests Cooch (1965) observedthat only about 15% of Common Eider nests were destroyedby predators.In Oldsquawsabout27.8% of all nestswere 48 ORNITHOLOGICAL MONOGRAPHS NO 18 predator-destroyed.Although Common Eiders tend to remain at the nest more or lesscontinuously(Cooch 1965), Oldsquawsfrequentlyleave their nests,especiallyon warm days,for severalhours Assumingthat a temporarily desertednest is more susceptible to destructionby predatorsthan a nestwith the femalepresent(given the predatoris only an eggpredatorand will not kill the adult female), the differing egg lossesdue to predation mighthave resultedfrom femaleOldsquaws'prolongedabsences from their nests ACKNOWLEDGMENTS Specialthanksare dueJon C Barlowfor his adviceand supportthroughout this study Financial supportwas providedto me througha post-graduatescholarship by the National ResearchCouncil of Canada while I attendedthe University of Toronto SUMMARY The breedingbiologyand behaviorof the Oldsquawwere investigated at Churchill, Manitoba, from 1968, through 1971 The breedingpopulation in the studyarea comprisedabout45 pairs of Oldsquawsin eachyear and thesealwaysarrivedbetween1 June and 23 June The birds invariablywere pairedon arrival Severalnonbreeding individuals,mostlysubadultsand adult females,were alsoresidentin the studyarea until July of each year Whereas adultdrakeshave alwaysleft the studyareaby 30 July, someducksand broods remaineduntil 31 August, in someinstances.Mortality of adult drakeson the breedinggroundsaveraged1.5% annually whereasthe female mortality was nil In eachyear of the study,individualswere captured,banded,and released Of these,13 femalesand two maleswere recapturedin the studyarea in subsequentyears Severalfemalesnestedat the samenestsite as in a previous year One drake was captured in four consecutiveyears on the same pond Adult drakeswere intraspecifically territorial, althoughduckstook no active part in territorial defense I suggestthat territorialityfunctionsto limit local breedingpopulation density in this species Courting males perform Lateral Head-shaking (LHs), Bill-tossing (Bt), Rear End Display (RE), Porpoising(P), Wing-flapping(Wf), Body-shaking (Bs), ParachuteDisplay (PD), Breast Display (BD), Turning-the-back-ofthe-head(BH), Bill-dipping(Bd), Steaming(S) and Neck-stretching (Ns) Of these,BilMossing,Rear End Display and Steamingare accompaniedby uniquevocalizations andBill-tossing andRear End Displayare species-specific visible displays The female performs Chin-lifting (C1), Soliciting (So), Hunch (Hu) and Steaming(S) 1975 ALISON: OLDSQUAW BIOLOGY 49 Bill-tossing is the mostcommondrakepre-copulatory displaywhereasfemalesmostfrequentlyperformChin-lifting.LateralHead-shaking is the most commonpost-copulatory displayof bothsexes.Courtshipbehaviorin paired malesis limitedto oneor two displaysper hour By contrastnon-pairedmales mayperform30 to 50 displays per hour Bill-tossing andLateralHead-shaking arethe mostfrequentlypreformedindividualdisplays.Occasionally, consistentsequences of two or threeindividualdisplaysare performed The Oldsquawis one of the first speciesof waterfowlto form pairs,and by mid-Februaryabout40% of the adultdrakesare paired Early pair-formation is encouragedby the shortnessof the Arctic breedingseasonand by the prolongedpost-nuptialmolt, which occurssubsequent to pair-formation The locationsof 95 nestsare described.In someinstances,especiallyon islands,nestswere clusteredand other nestswere isolated One instanceof intraspecificparasitismwas recorded There was no significantdifference betweenthe numberof individualnestson islandsas comparedwith mainland nests,and 58.9% of activenestswerefound on islands The speciestendedto nestin traditionallocations,especially on traditionalislands.Nest sitetenacity was apparentlynot relatedto previoussuccess or failure at a specificsite Whereascertainislandshad activeOldsquawnestsin each,45 out of 79 islands showedno evidenceof active or previousOldsquawnests Mainland nests were significantlybetter concealedthan island nests.Although some nests were situated close to water, over 80% were within 6.1 m of the edge of a pond or lake On islandsthere was a positive associationbetween Oldsquawnestsand Arctic Tern nests,whereason the mainlanda significant disassociation of the nestsof thesetwo specieswas observed.There was no significantdifferencebetweenOldsquawnest loss by predationon islands with activeArctic Tern nestsas comparedto islandswhere terns were not resident,but this studyalone is equivocalon this point I suggestthat the observedpositiveassociation of the two speciesprobablyresultsfrom similar nestingrequirements and preferences on islandsand isolatedpeninsulas The nest site was selectedby the female and the nest was constructed immediatelyprior to the depositionof the first egg Eggswere laid at intervals of about 26 hoursuntil the clutchwas complete The averageclutch size was 6.8 eggs Nearly 20% of the eggsof this specieswere nonviable From 1968 to 1971, the mean datesof clutch commencementwere 12 June, 23 June, 11 June, and June, respectively,and it was found that severeMay temperaturescould significantlydelay nest initiation Egg lossapparentlywas not relatedto weathervariations Predationwas the major causeof nest loss (26.4%), and the Oldsquawnestslocated on islandswere as frequentlydestroyedas mainlandnests Nests locatedon certainspecificislandsweredestroyedeachyear and nestslocatedon certain other islandswere always successful 50 ORNITHOLOGICAL MONOGRAPHS NO 18 The incubationperiod of Oldsquaweggswas 26- 0.8 days and about 58.9% of all eggshatchedsuccessfully The time requiredfor eachclutchto hatch(betweenthe hatchingof the first and last eggs)varied considerably amongclutchesbut about 30% of all clutchesrequired48 hoursto hatch completely The territorial behaviorof 10 adult male Oldsquawswas investigated Althoughadultmaleswere intraspecifically territorial,femalestook no active part in territorialdefenseand in mostinstances nestedin loosecolonies I suggest that a maximumnumberof suitableterritoriesexistsand that at maledensities greaterthan this, somemalesare preventedfrom establishing territoriesby residentmales,whereasothersmay defendlesspreferredterritories,perhapsin lesssuitablehabitat As the suitabilityof the habitatdeclines, thepotentialfor highproductivity probablydecreases The highestreproductive success shouldoccurin preferredhabitats.Territorialbehaviorin this species seemsto limit localbreedingpopulationsize LITERATURE ALISON,R.M CITED 1970 The behaviorof the Oldsquaw(Clangula hyemalisLinnaeus) Aves: Anatidae in winter UnpublishedM.S thesis, Toronto Univ Toronto ALISON,R M 1972 The breedingbiology of the Oldsquaw (Clangula hyemalis Linnaeus) at Churchill, Manitoba UnpublishedPh.D dissertation,Toronto, Univ Toronto ANI)ERSON,W 1956 A waterfowl nesting study in the grassland,Merced County, California California ANI)ERSON,W Fish and Game 42: 117-130 1957 A waterfowl nesting study in the Sacramento Valley, Cali- fornia, 1955 California Fish and Game 43: 71-90 BENT, A.C 1925 Life historiesof North American wildfowl, order Anseres,vol U.S Natl Mus Bull 130: 32-50 BERGMAN, G., ANDK C DONNER 1964 An analysisof the springmigrationof the Common Scoterand the Long-tailedDuck in southernFinland Acta Zool., Fennica 105: 1-59 BIRCH,L.C 1960 The geneticfactor in populationecology Amer Naturalist 94: 5-24 BOY1),H 1957 Movementsof marked sea and diving ducks in Europe Wildfowl Trust, Ann Rept 12 BROWN,J L 1969 Territorial behavior and population regulation in birds A re- view and re-evaluation COOCH,F G Wilson Bull I00: 371-376 1965 The breeding biology and managementof the Northern Eider (Somateriamollissimaborealis) in the Cape Dorset area, NorthwestTerritories Wildl Mgmt Bull Ser 2(10) COTTAM,C 1939 Food habits of North American diving ducks U.S Dept Agric., Tech Bull 643 DeLAcotm, J 1959 The waterfowl of the world, vol London, Country Life Ltd DRURY,W H 1961 Observationson some breeding water birds on Bylot Island Canadian Field-Naturalist 75: 84-108 1975 ALISON: EARL,J.P OLDSQUAW BIOLOGY 51 1950 Productionof Mallards on irrigated land in the SacramentoValley, California.J Wildl Mgrnt.14: 332-342 ERSKINE, A.J 1961 Nest-sitetenacityand homingin the Bufflehead Auk: 389-396 ERSKINE,A J 1966 Cape Breton Island waterfowl studies Canadian Wildl Serv Spec Rept '66 EVANS,R.M 1970 Oldsquawnestingin associationwith Arctic Terns at Churchill, Manitoba Wilson Bull 84: 383-390 FOLEY, D 1954 Survival and establishment of waterfowl released as ducklings New York Fish and Game J January 1954: 206-213 FRETWELL, S D., AND H L LUCAS 1969 On territorial behavior and other factors affecting habitat distribution in birds Theoretical development Acta Biotheoret 19: 16-36 GODFREY,W.E 1966 The birds of Canada Natl Mus Canada Bull No 203 GOLLOP, J B 1954 Waterfowl breeding ground survey in Saskatchewan 1953, special study area Kindersley-Eston Waterfowl populationsand breeding conditions-summer 1953 U.S Fish Wildl Serv and Canadian Wildl Serv., Spec Ser Rept.-Wildl HILDEN, O 25: 65-73 1965 Habitat selection in birds Ann Zool Fennica 2: 53-75 HULL, E D 1914 Habits of the Oldsquaw (Harelda hyemalis) in Jackson Park, Chicago Wilson Bull 26: 116-123 ISAAC,D., AND P MARLER 1963 Ordering of sequencesof singing behavior of Mistle Thrushesin relationshipto timing Anim Behav lI: 179-188 JEHL,J R., JR., ANDB A SMITH 1970 Birds of the Churchill region, Manitoba Manitoba Mus of Man and Nature, Spec Publ No JOHNSGARn, P.A nell Univ 1965 Handbookof waterfowl behavior Ithaca, New York, Cor- Press JOHNSOda,n, P A Univ Nebraska KEiTH,L.B 1968 Waterfowl: their biology and natural history Lincoln, Press 1961 A studyof waterfowlecologyon smallimpoundments in south- easternAlberta Wildl Monogr 6, October 1961 KORTRIGHT, F.H 1953 The ducks,geeseand swansof North America Harrisburg, Pennsylvania, Stackpole KOSKIMIES, J 1957 Terns and gulls as featuresof habitat recognitionfor birds nesting in their colonies Ornis Fennica 34: 1-6 LAC•C, D LAC•C,D 1954 The natural regulationof animal numbers Oxford, ClarendonPress 1966a The significanceof clutch-sizein waterfowl Wildfowl Trust Ann Rept 18 LAC•C,D L•so•, 1966b Population studiesof birds Oxford Clarendon Press S 1960 On the influenceof the arctic fox (AIopex lagopus) on the dis- tribution of arctic birds LOKEMOE?4, T Oikos 11: 276-305 1966 Breeding ecology of the Redhead duck in western Montana J Wildl Mgmt 30: 668-681 Low, J.B Iowa 1945 Ecology and managementof the Redhead, Nyroca americana, in Ecol Monogr 15: 35-69 MACKAY,G.H 1892 Clangula hyemalisin New England Auk 2: 330-337 M^RLER, P 1960 Bird songs and mate selection Pp 348-367 in Animal sounds and communications(W E Lanyon and W V Tavolga, Eds.) Publ No 7, Washington, D.C., Amer Inst Biol Sci M•X•ER, P A•r) ISAAC,D 1960 Physicalanalysisof a simple bird song as exempli- fied by the Chipping Sparrow Condor 62: 124-135 52 ORNITHOLOGICAL MONOGRAPHS NO 18 McKINNEY, F 1961 An analysis of the displays of the European Eider (Somateria mollissima mollissima Linnaeus) and the Pacific Eider ( Somateria mollissima v nigra Bonaparte) Behavior, Suppl MmLnis, J G 1913 Brit Diving Ducks London, Longmans, Green MINCER,A W., n•q•)B D Co•x•qs 1954 A nesting study of ducks and coots on Tule Lake and Lower Klamath National Wildlife Refuges California Fish and Game, 40: 17-37 MsmEs, M.T 1959 The behavior of the sea ducks and its value in the systematics of the Tribes Mergini and Somateriini,of the Family Anatidae Ph.D dissertation, Univ Vancouver, British Columbia P•I•LXPS, J C 1925 The natural history of the ducks, vol Boston, Houghton Mifflin Co Pm•xPs, J C 1928 The crow in Alberta and the work of the American fowlers Trans North Amer Game Conf 15: 146-151 wild POLUNIN, N 1967 Introduction to plant geography London, Longmans Rắ)F, J.P 1969 Nesting colonies of Ross' Goose Auk 86: 282-292 Sn•omo•qst•q, F 1950 The birds of Greenland Copenhagen, Ejnar Munksgaard Sc•oRatg, A.W 1947 The deep diving of the loon and Oldsquaw and its mechanism Wilson Bull., 59: 151-159 Scoaan•q,H J 1959 The native flora of Churchill, Manitoba, with notes on the history, geology, and climate of the area Guide book, Nail Mus Can Sow•s, L.K 1955 Prairie ducks Washington,D.C., Wildl Mgmt Inst S•tL, P E., P D Dn•ICt, n•q•) E.G Blzv•u 1956 Duck production at Gray's Lake, Idaho, 1949-1951 J Wildl Mgmt 20: 279-285 SuTro•, G.M 1932 Notes on molts and sequenceof plumagesin Oldsquaws.Auk 49: 42-51 Tx•qBEgat•q,N 1959 Comparative studies of the behavior of gulls (Laridae): a progress report Behavior 15: 1-70 VERMtER, K larids 1968 Ecological aspects of ducks nesting in high densities among Wilson Bull 80: 78-83 No 15 Functional Anatomy and Adaptive Evolution of the FeedingApparatus in the Hawaiian HoneycreeperGenusLoxops (Drepanididae),by Lawrence P Richards and Walter J Bock vii + 173 pp., 14 text figures + 26 plates 1973 Price $9.00 ($7.50 to AOU members) No 16 The Red-tailed Tropicbird on Kure Atoll, by RobertR Fleet vii + 64 pp., 34 text figures, tables 1974 Price $5.50 ($4.50 to AOU members) No 17 ComparativeBehaviorof the AmericanAvocetand the Black-necked Stilt (Recurvirostridae), by Robert Bruce Hamilton, vi + 98 pp., 18 text figures 1975 Price $7.50 ($6.00 to AOU members) No 18 BreedingBiologyand Behaviorof the Oldsquaw(ClangulabyemallsL.), by Robert M Alison, vi + 52 pp., 13 text figures 1975 Price $3.50 ($2.50 to AOU members) Like all other AOU publications,OrnithologicalMonographs are shipped prepaid Make checkspayable to "The American Ornithologists'Union." For the convenience ofthose whowishtomaintain complete sets ofOrnithological Monographs andtoreceiv[ new numbers immediately upon issue, standing orders will be accepted Order from: Glen E Woolfenden, Assistantto the Treasurer AOU, Department of Biology,University of South Florida, Tampa, Florida gg6•0 ORNITHOLOGICAL No MONOGRAPHS A Distributional Study of the Birds of British Honduras, by StephenM Russell 195 pp., color plates 1964 Price $7.00 ($5.50 to AOU members) No A Comparative Study of Some Social Communication Patterns in the Pelicaniformes, by Gerald Frederickvan Tets 88 pp., text figures 1965 Price $3.50 ($2.50 to AOU members) No The Birds of Kentucky, by RobertM Mengel Cloth bound,xiv q- 581 pp., color plates plus text figures and vignettes 1965 Price $15.00 ($12.50 to AOU No members) Evolution of Some Arctic Gulls (Larus): an Experimental Study of Isolating Mechanisms,by Neal Griffith Smith 99 pp., 62 text figures 1966 Price $4.00 ($3.00 to AOU members) No A ComparativeLife-historyStudy of Four Speciesof Woodpeckers,by Louise de Kiriline Lawrence 156 pp., 33 text figures 1967 Price $6.00 ($4.50 to AOU members) No Adaptations for Locomotion and Feeding in the Anhinga and the Double-crestedCormorant, by OscarT Owre 138 pp., 56 text figures 1967 Price $6.00 ($4.50 to AOU members) No A Distributional Survey of the Birds of Honduras, by Burr L Monroe, Jr 458 pp., 28 text figures, color plates 1968 Price $14.00 ($11.00 to AOU No members) An Approachto the Studyof EcologicalRelationshipsamongGrassland girds, by John A Wiens 93 pp., 30 text figures 1969 Price $4.00 ($3.00 to AOU No members) Mating Systems,Sexual Dimorphism, and the Role of Male North American PasserineBirds in the Nesting Cycle,by JaredVernerandMary F Willson 76 pp 1969 Price $4.00 ($3.00 to AOU members) No 10 The Behavior of SpottedAntbirds, by EdwinO Willis,vi + 162 pp., color plates, 27 text figures 1972 Price $9.00 ($7.50 to AOU members) No 11 Behavior, Mimetic Songsand Song Dialects,and Relationshipsof the Parasitic Indigobirds (¾idua) of Africa, by Robert B Payne,vi + 333 pp., color plates, 50 text figures, 40 audiospectrographs 1973 Price $12.50 ($10.00 to AOU members) No 12 Intra-islandVariation in the MascareneWhite-eyeZosterops borbonica, by Frank B Gill, vi q- 66 pp., color plate, 31 text figures 1973 Price $3.50 ($2.50 to AOU members) No 13 EvolutionaryTrends in the Neotropical Ovenbirdsand Woodhewers,by Alan Feduccia, iv + 69 pp., 20 text figures 1973 Price $3.50 ($2.50 to AOU members) No 14 A Symposiumon the House Sparrow(Passerdomesticus)and European Tree Sparrow (P montanus) in North America, S CharlesKendeigh chairman vi + 121 pp., 25 text figures 1973 Price $6.00 ($4.50 to AOU members) (Continued on inside back cover) ... OLDSQUAW (CLANG {_/L•I HYœA4t•ILIS L ) BY ROBERT ORNITHOLOGICAL M ALISON MONOGRAPHS PUBLISHED THE AMERICAN BY ORNITHOLOGISTS' 1975 NO UNION 18 ORNITHOLOGICAL MONOGRAPHS This series,publishedby the AmericanOrnithologists'... Copiesof OrnithologicalMonographsmay be orderedfrom the Assistant Treasurerof theAOU, GlenE Woolfenden,Departmentof Biology,University of SouthFlorida,Tampa, Florida 33620 OrnithologicalMonographs,No... knownhistorywereincludedin the data (i.e exactdateof initiationof eachclutchwasknown) Oldsquaws 18 ORNITHOLOGICAL MONOGRAPHS NO 18 tendedto breedat traditionallocations.Consequently, by surveying eachof thesesitesdailyit
- Xem thêm -

Xem thêm: Ornithological Monographs 18, Ornithological Monographs 18

Gợi ý tài liệu liên quan cho bạn

Nhận lời giải ngay chưa đến 10 phút Đăng bài tập ngay