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Recognizable Forms

Redpollsby

Ron Pittaway

IntroductionThe American Ornithologists'

Union Check-list (1983) recognizestwo species of redpolls: CommonRedpoll (earduelis flammea) andHoary Redpoll (e. hornemannis.Each species has two well-markedsubspecies in Canada (Godfrey 1986).However, the taxonomy of redpollshas been much debated. Someauthors suggest lumping all redpollsinto a single species, while otherspropose splitting them into fourseparate species. Regardless of howmany species there are, classicindividuals of each of the four formsare recognizable in the field. Thelegendary George North of Hamiltonactually saw the four forms ofredpolls in one flock at Aldershot on23 March 1958 (North 1983)! In orderto recognize these forms, we requirea sound knowledge of the fieldmarks, plus a thorough understandingof redpoll plumages, effects of wear,age classes and molts. It is afascinating identification challenge,worthy of our consideration.

TaxonomyThe Common Redpoll has two

subspecies in Canada: the smallerand southern nominate race (e. [.flammeai and a larger northern race(e. t. rostrata). A third race, e. t.holboelli, is considered by mostauthorities to be of doubtful validity(AOU 1957, Godfrey 1986). Knox

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(1988) treats it as representing verylong-billed individuals of nominate e.r [lammea. The Hoary Redpoll alsohas two subspecies in Canada: asmall southern race (e. h. exilipes)and the larger northern nominaterace (e. h. hornemannii.

Troy's (1985) widely read andmuch quoted study concluded thatthe southern race of the CommonRedpoll (e. [. flammea) and thesouthern race of the Hoary Redpoll(e. h. exilipes) should be lumped asone highly variable species. Hisassumption was that intermediatebirds represented hybrids. This viewappealed to many ornithologists,birders and banders who had foundthemselves perplexed by redpollidentification. However, laterresearchers questioned Troy'staxonomic conclusions. Seutin et al.(1989) noted that Troy failed "to takeage dimorphism into consideration inhis analysis". In fact, Knox (1988)could find no direct evidence ofhybridization anywhere in the largearea of overlap between Commonand Hoary Redpoll populations,although he suspected that occasionalhybridization does occur. Based onbiochemical evidence(electrophoresis). Marten and Johnson(1986) found that the two mostsimilar forms of Common Redpoll (e.r [lammeai and Hoary Redpoll (e. h.exilipes) "seem to have split 550,000

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Figure 1: Adult male Common Redpoll. Drawing by Chris Kerrigan.

years ago". These two forms "areclearly near the boundary of speciesformation" (Knox 1988). Both Knox(1988) and Herremans (1989)considered the two forms to be a pairof sibling species. Sibling species aretwo or more closely related speciesthat have very similar morphology.The Empidonax flycatchers are a goodexample of sibling species. Similarly,

the two large northern redpolls (c. h.homemannii and C. f. rostrata) alsooccur together over a wide area withvirtually no evidence ofinterbreeding. Previously, Todd(1963) and recently Herremans (1989)have proposed four species ofredpolls: C. hornemanni, C. exilipes, C.rostrata and C. f/ammea. See Figure 2.

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Plumages, Molts and AgeingA knowledge of redpoll plumages

will help in understanding thevariation seen in redpoll flocks.Instead of resulting fromhybridization, much of the confusionover intermediate birds can beexplained by age and sex differences,and individual variation (Knox 1988).The following is only a generaloutline of the plumages, molts andages in redpolls.

Adult (definitive basic) redpollsundergo a complete molt (all feathers)once a year after the breeding season.Because of buffy or greyish featheredges which gradually wear off,adults in fresh (new) fall plumage aremuch paler than the same birds inworn (old) breeding plumage. Inmales, the pink coloration is also palewhen fresh, gradually becomingricher and redder by spring. Featherwear allows redpolls to don abreeding dress without the need tomolt (Newton 1972). This change iswell illustrated in the NationalGeographic Society's Field Guide(Scott 1987). Compare theillustrations of the Common Redpollslabelled winter and breeding on page439.

Juveniles lack the red cap andblack chin of the adult birds. On thebreeding grounds in late summer,juveniles undergo a partial (body)molt to first year (first basic)plumage retaining most of thejuvenile wing and tail feathers.Seasonally compared, first year birdsare darker and more streaked thantheir respective adults. Redpolls weartheir first year plumage forapproximately one year, after whichthey molt completely into adult ordefinitive basic plumage.

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A large flock of "Southern "Common Redpolls (c. f. flammeai willshow four plumage types: adultmales, adult females, first year males,and first year females. Add anotherform to the above flock and nowthere are eight possible plumagetypes!

"Southern" Common Redpoll{e. f. {lammeaJ

This low Arctic form breedssouth to northern Ontario (James1991). It is an erratic winter visitor tosouthern Ontario, sometimes in largenumbers. This is the commonestform in the province, faroutnumbering the other three formsand is the standard by which theother forms are compared andrecognized. Study the flocks (birdfeeders are ideal) and learn thedifferent plumage variations. Adultmales are richly coloured with rosypink while first year males aresomewhat darker and often washedwith light pink. Adult females on theother hand usually lack any pinkcolouration (sometimes tinged) andfirst year females are the darkest andmost heavily streaked of the ageclasses, at times almost siskin-like.

In all plumages, this form isusually noticeably streaked on thesides, rump and undertail coverts.The bill is longer and less stubbythan the Hoary'S. Individualsshowing characteristics that areintermediate between C. f. f/ammeaand C. h. exilipes are best leftunidentified.

"Greater" Common Redpoll{e. f. rostrata]

This large and dark form breedson Baffin Island and Greenland (Todd

C§e-cs:t'l

c. f rostrata C. h. hornemanni

c. f flammea C. h. exilipes

ozcs:cct'l

"w Figure 2: Common Redpolls [left] and Hoary Redpolls [right}, Drawing by Michel Gosselin.•....•....•....

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1963). In parallel with the twosubspecies of the Hoary Redpoll,there is also a gap between thebreeding ranges of the two subspeciesof the Common Redpoll. See therange map in Godfrey (1986). It is awinter visitor "in small numbers tosouthern parts of the East fromOntario to Newfoundland" (Godfrey1986). Richard Poulin [pers. comm.]has banded hundreds of redpolls nearOttawa, and reports that "Greaters"are more common than HoaryRedpolls during some winters. Lookfor this distinctive subspecies duringredpoll flight years.

The "Greater" is somewhat larger(averaging 14.0 cm) than the"Southern" race which averages 12.5cm in length (Newton 1972). Thedifference between the two races ofthe Common Redpoll is "fairlyobvious when the two birds aretogether in the same flock" [Peterson1947). "Greater" field marks include"larger size with thicker bill,coloration somewhat darker andbrowner than in flammea, adult maleswith red of under parts less extensiveand less intense" (Godfrey 1986).Observers familiar with "Greaters"in the field have described them assomewhat House Finch-like becauseof their stout bills, heavy builds andgeneral darker colouration withconspicuous streaking on theunderparts.

"Southern" Hoary Redpoll{C. h. exilipes]

This form breeds in the lowArctic, and much of its rangeoverlaps that of the "Southern"Common Redpoll. It breeds regularlysouth to Churchill, Manitoba (Jehland Smith 1970), and Middleton (in

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Cadman et al. 1987) reported that it"may breed in low numbers on thetundra of Hudson Bay" in Ontario.During redpoll flight years, it isusually possible to find a few"classic" adult males. They stand outby their very white "frosted"appearance, pure white rumps, palerand less extensive pink suffusion onthe breast, lightly streaked flanks,and very lightly streaked toimmaculate undertail coverts."Southern" Hoaries are similar insize to "Southern" Commons, butusually have shorter, more obtuse(stubby) bills imparting a distinctive"pushed in face" appearance. Manyfirst year and some adult female"Southern" Hoaries can be quitestreaked on the rump and sides (Knox1988). These "intermediate birds" areprobably best treated as unidentified.The reader is referred to the excellentarticle by Lansdown et al. (1991) onthe identification of this form.

"Hornemann's" Hoary Redpoll{C. h. hornemanni]

The "Hornemann's" or"Greenland" Hoary Redpoll is thelargest and palest of the redpolls(Godfrey 1986). There is apparently agap between the breeding range ofthe two subspecies of the HoaryRedpoll [Todd 1963). This race breedsin the Canadian high Arctic andGreenland and "is a great raritysouth of the tundra at any season"(Aubry et al. 1987). The AmericanOrnithologists' Union Check-list(1957) lists a record from Galt(Cambridge), Ontario. The specimenis now in the Royal Ontario Museum(North 1983). (See North's account ofthis specimen and his observation of

the four forms of redpolls in thePostscript to this article. 1

"Hornemanns" Hoary Redpoll isa larger bird (averaging 14.0 cm] thanthe "Southern" Hoary whichaverages 12.5 cm in length (Newton19721.Todd (19631states that there is"no overlap in measurements"between the two subspecies.Compared to the "Southern" HoaryRedpoll, "Hornernann's" is known byits larger size, overall whiterappearance, less prominent streakingon the sides and flanks, andimmaculate undertail coverts; maleshave less pink which is of a differenthue, some showing a mere trace ofpink suffusion on the breast (Todd19631.Females and first year birdsare probably recognizable, if directlycompared to the other forms(especially the two smaller ones], bytheir pale colouration and larger size.Richard Poulin (pers. comm.] hasobserved this form in the high Arctic.He describes it as being "reallydistinctive; a big, very white redpollsuggesting a Snow Bunting"!

SummaryCommon and Hoary Redpolls

appear to be valid species. The"intermediate birds" reportedbetween C. f flammea and C. h.exilipes are apparently the result ofage, sex and individual variation andnot interbreeding. Some authoritiesrecognize four species of redpolls.Not all redpolls will be identifiable tospecies or subspecies, but "classic"individuals of each form are veryrecognizable.

PostscriptGeorge North's (19831description

of his experience with redpolls is

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worth quoting here, as an example ofhis interest in recognizable forms:

"The McIlwraith Loan Collectionof birds used to be housed in theHamilton Museum on the secondfloor of the old Public Library andArt Gallery which stood on the eastside of Centenary Methodist Church.Back in the 1920's I used to visit themuseum often to admire the birdsand study them carefully. Among themost striking was the big whiteGreenland Redpoll, that seemed to beas big as a Snow Bunting. It wascollected about 1863 by a friend ofMr. McIlwraith's from a small flockin the town of Galt.

For many years I searched the bigor small flocks of redpolls that visitedus almost every winter, but withoutsuccess in finding this big and hoarybird. Then on March 23, 1958, onone of our weekly birding tripstogether, Dr. R.G.C. MacLaren and Ivisited a spot that had produced goodbirds in previous springs. This was anextensively open field off the PlainsRoad at Aldershot that was part ofthe property of Mrs. Towsend's atOaklands. On walking over the fieldwe came on a flock of redpollsfeeding on weed seeds. To our delightthere was a big white redpoll, twiceas big as the Common Redpolls, theGreenland Redpoll that I had beensearching for for thirty years. But thiswas not the only rare bird there. Onlooking over the flock we found onespecimen of the commoner smallwhite-rumped Hoary Redpoll and oneindividual of the Greater Redpoll.This latter is classified as a subspeciesof the Common Redpoll, but it is amuch larger bird, more the size of aPurple Finch and has a much heavierbill, more like a grosbeak's. I have

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seldom seen the Greater Redpollsince the winter of 1929-30 when Ifound them on the north shore of theDundas Marsh."

AcknowledgementsI thank Bill Crins, Bob Curry,

Bruce DiLabio, Michel Gosselin,Brian Henshaw, Henri Ouellet,Richard Poulin, Ron Tozer and MikeTurner. I wish to especially thankRon Tozer for his critical review ofthe manuscript and assistance withthe literature search. I also thankMike Turner for his critical review ofthe manuscript and for logisticalsupport. Michel Gosselin supplied mewith much valuable information aswell as kindly allowing me to use hissuperb illustrations which previouslyhad been published (in part] inAmerican Birds. I thank ChristineKerrigan for her fine sketch of themale Common Redpoll.

Literature citedAmerican Ornithologist's Union. 1957.

Check-list of North American Birds, 5thedition. American Ornithologist's Union,Washington, D.C.

A •••erican Ornithologist's Union. 1983.Check-list of North American Birds, 6thedition. Alien Press Inc., Kansas.

Aubry, Y., M. Gosse/in, and R. Yank. 1987.The fall season, Quebec region. AmericanBirds 41: 406.

Cadman, M.D., P.F.]. Eagles, F.M. Helleiner{compilers}. 1987. Atlas of the Breeding Birdsof Ontario. University of Waterloo Press,Waterloo, Ontario.

Godirey, W.E. 1986. The Birds of Canada.Second Edition. National Museum of Canada,Ottawa.

Herremans, M. 1989. Taxonomy and evolutionin redpolls. Ardea 78: 441-458.

[ames, R.D. 1991. Annotated Checklist of theBirds of Ontario. Second Edition. LifeSciences Miscellaneous Publications,Royal Ontario Museum, Toronto.

jehl, j.j. and B.A. Smith. 1970. Birds of theChurchill Region, Manitoba. Special Public-ation Number 1, Manitoba Museum of Manand Nature, Winnipeg.

Knox, A.G. 1988. The taxonomy of redpolls.Ardea 76: 1-26.

Lansdown, P., N. Riddiford and A. Knox, 1991.Identification of Arctic Redpoll Carduelishornemanni exilipes. British Birds 84: 41-56.

Marten, j.A. and N.K. [ohnson. 1986. Geneticrelationships of North American Carduelinefinches. Condor 88: 409-420.

Newton, I. 1972. Finches. Collins, London.North, G. W. 1983. Greenland Redpoll.

The Wood Duck 36: 119.Peterson, R. T. 1947. A Field Guide to the Birds.

Houghton Mifflin Company, Boston.Scott, S.L. [ed.]. 1987. Field Guide to the Birds

of North America. National GeographicSociety, Washington, D.C.

Seutin, G., P. T. Boag and L.M. Ratcliffe.1989. Plumage variability in North Americanredpolls [Aves: Carduelinae): the importanceof sexual and age dimorphisms. The Musk-ox37: 116-121.

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

Troy, D.M. 1985. A phenetic analysis of theredpolls Carduelis flammea [lammea andC. hornemanni exilipes. Auk 102: 82-96.

Ron Pittaway, Box 619, Minden, Ontario KOM2KO