23

Recognizable Forms

Subspecies of the Palm Warblerby

Ron Pittaway

IntroductionW. Earl Godfrey (1986) in The Birdsof Canada says about the PalmWarbler (Dendroica palmarum)."There are two subspecies, oneeastern, one western, differentenough to be recognizable in thefield". The two subspecies (races) ofthe Palm Warbler are illustrated byPeter Burke in Figure l. See alsoPlate 7 in Curson et al. (1994). page369 in the National Geographic Guide[Scott 1987). pages 287 and 295 in theGolden Guide [Robbins et al. 1983)and page 239 in Peterson (1980). Inthe following account I discuss theidentification, distribution, migrationtimes and routes, winter ranges, andstatus of the two subspecies of thePalm Warbler in Ontario.

TaxonomyThe American Ornithologists' UnionCheck-list (1957) and Godfrey (1986)list two subspecies of the PalmWarbler: the nominate "Western"subspecies D. p. palmarum andthe eastern "Yellow" subspeciesD. p. hypochrysea. The two subspeciesdiffer in so many ways that Todd(1963) stated "I strongly suspect thatwe are dealing with two closely alliedbut separate species". Todd's opinion(before intergradation was well-established) serves to demonstrate thedistinctiveness of the two subspecies.See also discussion under Intergrades.

Plumages, Molts, Ageingand SexingThe sexes are similar in all ages andplumages. The briefly held juvenile[juvenal] plumage is seen only on thebreeding grounds. Juveniles undergoa partial molt to first winter (firstbasic) plumage before fall migration.First winter birds begin their partialmolt in mid-winter to first summer(first alternate) plumage, and theybreed in this plumage. Adult winter(definitive basic) birds also beginacquiring adult breeding (definitivealternate) plumage in mid-winter.First summer and adult breedingplumages are very similar inappearance. Because these birdsusually cannot be aged in the field, itis best to refer to them collectively asbeing in breeding (alternate) plumage.After breeding but before fallmigration, both first summer andadult breeding birds undergo acomplete molt to adult winterplumage. Autumn migrants consist ofbirds in first winter and adult winterplumages. These plumages are oftenbest treated collectively as winter orbasic plumage.

Western Palm Warbler{D. p. palmarum]The Western Palm Warbler breeds in"western and central Canada east toMoosonee and Kapuskasing, Ontario"(Godfrey 1986). It is a common

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migrant in southern Ontario [james19911.For the Oshawa-Lake Scugogarea, Tozer and Richards (19741saythe (Westernl Palm Warbler is "Afairly common spring and falltransient (early May to mid-May:mid-September to early October I ...but in low numbers" .

Most Western Palm Warblers inbreeding [alternate] plumage areeasily distinguished from YellowPalm Warblers (with entireunderparts yellow I by their whitishor only faintly yellowish bellieswhich contrast with the rest of theunderparts (Figure 11.See also thephotograph of a Western Palm inbreeding plumage on page 155 inVolume 3 of the Master Guide(Farrand 198'31.Western Palms inwinter [basic] plumage are muchduller than Yellow Palms; the yellowundertail coverts contrast with thewhitish (or tinged yellow I underpartsof adults or the buffy whiteunderparts in fresh first winter birds.By learning the plumage variation inthe Western Palm Warbler you willbe prepared to find the much rarerYellow Palm Warbler in Ontario.

Yellow Palm Warbler(D. p. hypochryseaJThe subspecies name hypochryseameans "golden beneath" (Bent 19531.The Yellow Palm Warbler breeds in"eastern Canada west to LakeMistassini, Quebec and Ottawa,Ontario" (Godfrey 19861.The Ottawa(Mer Bleue Bog] population isapparently extirpated (Earl Godfrey,pers. comm.]. However, a few maystill breed in other large bogs ofeastern Ontario. Don Sutherland(pers. comm.] observed a singingmale Yellow Palm Warbler insuitable breeding habitat in Stormont

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County on 23 June 1984. The YellowPalm is a rare migrant in southernOntario west to Point Pelee [james19911.For example, they have beenrecorded at Ottawa, Kingston,Toronto, Hamilton and Long Point.

Yellow Palm Warblers tend tomigrate earlier in spring and later infall than Western Palms {Dunn 19941.A Palm Warbler in southern Ontarioin mid to late April or after mid-October could be a Yellow Palm!

Typical Yellow Palm Warblers inbreeding [alternate] plumage areeasily told from Western Palms bytheir entirely yellow underparts(Figure 11.See also the excellentphotograph on page 992 in Terres(19821. In addition, Yellow Palmshave broad chestnut or reddishstreaking on the underparts, whereasWestern Palms have finer darkbrown streaking. Yellow Palms alsohave more greenish-olive upperpartsthan Western Palms. In winter [basic]plumage, most Yellow Palms can beseparated from Western Palms bytheir much yellower underparts(Godfrey 19861and usually yellowishinstead of whitish superciliary line(Bent 19531. See the illustrationcomparing both subspecies in basicplumage on page 295 in the GoldenGuide (Robbins et al. 19831.

IntergradesThe zone of intergradation betweenthe two subspecies of the PalmWarbler is relatively narrow. Forexample, the breeding birds fromMoosonee and Kapuskasing, Ontario,are palmarum (Godfrey 19861;whereas birds from Lake Mistassini,Quebec, and eastern Ontario(Ottawa I are hypochrysea (Godfrey1949, 19861. However, breeding birds(five specimens I from Amos, Quebec

Figure 1: Top: Western Palm Warbler in breeding plumage (sexes similar).Bottom:Yellow Palm Warbler in breeding plumage (sexes similar).Drawing by Peter Burke.

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(about 140 km east of the Ontarioborder I are "almost exactlyintermediate between the two racesand show that the Amos region is anarea of intergradation" (Godfrey19681. Note that specimens from LakeSt. John, Quebec and Ottawa, Ontarioare referable to hypochrysea but showslight intergradation toward palmarum(Rand 1944, Rand 1948, GodfreyandWilk 1948, Todd 19631. In referenceto six specimens from Lake St. John,Quebec, Godfrey and Wilk (19481state they "differ somewhat fromhypochrysea from the MaritimeProvinces in the extent and intensityof the yellow coloration of theunderparts. In the two females theyellow ventral coloration is dull andrestricted, and in one is almostlacking on the abdomen and flanks.This specimen is practicallyinseparable from palmarum fromManitoba and Alberta, except for itsmore olivaceous upper parts. Theseries as a whole, however, isunquestionably closer tohypochrysea". The above locations areclearly shown on the map inside thehard cover of The Birds of Canada(Godfrey 19861.

As a final note, there is also someindividual variation in bothsubspecies in that a bright WesternPalm or a dull Yellow Palm might becalled an intergrade or confused withthe other subspecies (Earl Godfrey,Ross James and Don Sutherland, pers.comms.}.

Migration and WinterThe Western Palm Warbler and theYellow Palm Warbler winter indifferent areas and there is a curiouscrisscrossing of migration routes. TheYellow Palm spends the winter in theGulf States mostly west of Florida to

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Louisiana, and in spring crosses thesouthern Appalachian Mountains tomigrate northward east of themountains to northern New Englandand eastern Canada. The WesternPalm, leaving its winter home inFlorida and the West Indies, crossesthe southern Appalachians in theopposite direction usually south ofthe Carolinas, and migratesnorthward to Ontario and westernCanada. In fall, both subspeciescrisscross again en route to thewintering grounds. The Yellow Palmfollows the reverse of its spring route.However, the fall migration route ofthe Western Palm Warbler is moreeasterly and it usually outnumbersthe Yellow Palm along the AtlanticCoast at this time (Bent 1953, Bull1974, Griscom and Sprunt 1979,Dunn 19941.

SummaryTypical individuals of Western PalmWarbler and Yellow Palm Warbler,particularly in breeding plumage, areeasily distinguished in the field. TheWestern Palm Warbler is thecommon subspecies in Ontario.Intergrades are uncommon.

AcknowledgementsI am grateful to Peter Burke, BillCrins, Bruce Di Labio, Jon Dunn,Earl Godfrey, Michel Gosselin, RossJames, Jean Iron, Mike Turner, RonTozer and Gerry Smith for muchvaluable advice and assistance. [onDunn kindly made available a draftof the Palm Warbler text from hisupcoming book on warblers. PeterBurke is a wizard at being able toconvey differences in coloration in ablack-and-white medium.

Literature citedAmerican Ornithologists' Union. 1957.

Check-list of North American Birds, 5thEdition. American Ornithologists' Union,Washington, D.C.

Bent, A. C. 1953. Life Histories of NorthAmerican Wood Warblers. United StatesNational Museum Bulletin 203.Washington, D.C.

Bull, J. 1974. Birds of New York State.Doubleday/Natural History Press.

Curson, J., D. Quinn and D. Beadle. 1994.Warblers of the Americas, an IdentificationGuide. Houghton Mifflin Company, Bostonand New York.

Dunn, J.L. 1994. Comments on the 1992-1993Holmes County wintering warblers.The Ohio Cardinal 16: 70-71.

Farrand, J.F. Jr. (Editor/1983. The AudubonSociety Master Guide to Birding. Volume 2.Alfred A. Knopf, New York.

Godfrey, W.E. 1949. Birds of Lake Mistassiniand Lake Albanel, Quebec. Bulletin No. 114,National Museum of Canada, Ottawa.

Godfrey, W.E. 1968. Notes on Birds of the AmosRegion, Quebec. Natural History PapersNo. 44. National Museum of Canada, Ottawa.

Godfrey, W.E. 1986. The Birds of Canada.Revised Edition. National Museum ofCanada, Ottawa.

Godfrey, W.E. and A.L. Wilk. 1948. Birds of theLake SI. John Region, Quebec. BulletinNo. 110, National Museum of Canada,Ottawa.

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Griscom, L. and A. Sprunt, Jr. IRevised andUpdated by E.M. ReillyJ. 1979. The Warblersof America. Doubleday, New York.

[ames, R.D. 1991. Annotated Checklist of theBirds of Ontario. Second Edition. RoyalOntario Museum, Toronto.

Peterson, R. T. 1980. A Field Guide to EasternBirds. Houghton Mifflin Company, Boston.

Rand, A.L. 1944. Notes on the Palm Warbler,Dendroica palmarum [Gmelin], in Canada.Canadian Field-Naturalist, 58: 181-182.

Rand, A.L. 1948. Probability in subspeciesidentification of single specimens.Auk 65: 416-432.

Robbins, C.S., B. Bruun and H.S. Zim. 1983.Birds of North America. Golden Press,New York.

ScOIl, S. L. [ed.}, 1987. Field Guide to theBirds of North America. National GeographicSociety, Washington, D.C.

Terres, J.K. 1982. The Audubon SocietyEncyclopedia of North American Birds.Alfred A. Knopf, New York.

Todd, W.E.C. 1963. Birds of the LabradorPeninsula and Adjacent Areas. CarnegieMuseum and University of Toronto Press.

Tozer, R.G. andJ.M. Richards. 1974.Birds of the Oshawa-Lake Scugog Region,Ontario. Published by the Authors.

Ron Pittaway, Box 619, Minden, Ontario KOM2KO_

PUBLICATION NOTICE

Clive Goodwin has prepared a brief guide titled "Where to Watch Birds AroundCobourg", It is available from the Chamber of Commerce, 212 King Street West,Cobourg, Ontario K9A 2N1, free on receipt of a stamped, addressed No. 10envelope.

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