Photo Essay: Redpolls from Nunavut and Greenland visit Ontario ...

PHOTO ESSAY: REDPOLLS FROM NUNAVUT AND GREENLAND VISIT ONTARIOspecies simultaneously among gatherings ofthe more expected nominate Common Redpolland exilipes Hoary Redpoll.On 8 January 2011, Michael Butler, payingcareful attention to redpoll flocks in his backyardat Marathon, Ontario, on the northshore of Lake Superior, photographed aHornemann’s Redpoll. In reviewing his images,Butler noted that one bird in the backgroundappeared to be a Greater Redpoll, andanother in the foreground was an exilipesHoary (Figure 1). Experts in the identificationof redpolls, Ron Pittaway and MichelGosselin, agreed: all four taxa were visible—the first time the four North American taxawere known to have been photographed together!Following Butler’s discovery, it becameclear that redpolls of all sorts had madeit to northeastern Ontario as well, and BrandonHolden made his way to Matheson on 18February 2011, to discover at least fiveHornemann’s and many Greater Redpollsamong redpolls flocks at feeders. SouthernNew England and upstate New York hadscattered reports of Greater and Hornemann’sRedpolls, and many birders there got to observethese big redpolls for the first time.Along with many other web-based conversationsand shared images, Holden’s and Butler’swebsites, full of fine images of thesebirds, became the impetus for the presentPhoto Essay.In the history of North American Birds andits antecedent journals, the little-knownHornemann’s Redpoll has been mentioned infrequently,and black-and-white photographshave been published only twice, from Québec(Aubry et al. 1988) and possibly Pennsylvania(Brinkley et al. 1994). Generally acceptedrecords of Hornemann’s Redpoll extend southto Maryland and west as far as Michigan andManitoba, whereas records of exilipes HoaryRedpoll extend south to Virginia and muchfarther to the west, with records from SouthDakota, Nebraska, Wyoming, Idaho, Washington,and Oregon. Greater Redpoll has beendocumented in New England and the northernGreat Lakes region, with outlying recordsextending to southern New York and NewJersey; there are also single records from Coloradoand Maryland. Pittaway (1992) reportsthat Greater Redpolls are more common thanHoaries during some winters in southern Ontario.The relative abundance of Greater Redpollin the northeastern United States is notas well understood.With the rise of Internet-based communication,numerous observers have posted imagesof redpolls, including Hornemann’s andGreater, from their areas, along with observationsabout redpoll identification. As oftenoccurs, many of the formerly active hyperlinkshave become inactive, and some of thediscussion that remains archived in scatteredplaces includes misleading material and errors.There are numerous published articleson redpolls and their identification, andsome are readily available from their publishersor are even archived online. Some of theseare based on scientific studies, but manywere written by people who witnessed a redpollirruption in their areas. During the winterof 1993-1994, for example, Dave Czaplak(1995) studied hundreds of redpolls at hisGermantown, Maryland feeders—and documentednot just 17 exilipes Hoary Redpollsbut also at least one each of Greater andHornemann’s. In Ontario, Pittaway (1992)summarized what was known about theidentification of North American taxa basedon his extensive encounters with redpollsduring irruptions in Canada. In the UnitedKingdom, a 1984 irruption of nominateCommon and exilipes Hoary Redpolls wasthe occasion for a paper treating differencesbetween those taxa (Lansdown et al. 1991),and other authors have followed suit aftersubsequent redpoll flights in the UnitedKingdom (Riddington et al. 2000, Penningtonand Maher 2005).Using Michael Butler’s photographs fromOntario’s Thunder Bay District and BrandonHolden’s images from the Cochrane District(near the Québec border), this Photo Essayshowcases the High Arctic redpolls amongtheir smaller relatives and also illustratessome distinctions between Hoary and Common,whose identification continues to providechallenges. We look first at distinctionsbetween exilipes Hoary and nominate CommonRedpoll, then at differences betweenHornemann’s Redpoll and exilipes Hoary Redpoll,and lastly at differences between GreaterRedpoll and nominate Common Redpoll.Thankfully, Hornemann’s and Greater havevery dissimilar plumages, but a few of the imagesthat follow depict the two together.Redpoll identification: historyand cautionary considerationsAlthough most field guides to North Americanbirds illustrate basic differences betweentypical adult Common and Hoary Redpollsfairly well, the field marks emphasized inthese guides must often be used in conjunctionwith subtler characters to make a strongcase for identifying many individuals. Redpollplumages have been critically described in theAmerican scientific literature since Coues(1861) and Ridgway (1901). Various authorshave recognized between one and six speciesof redpoll, though most recognize just two inNorth America, Hoary and Common, thesebeing distinguished chiefly by plumage featuresrather than measurements. Troy (1985)collected redpoll specimens (nominate Commonand exilipes Hoary only) from Alaska tonorthern Québec and focused on streaking inundertail coverts, rump, and flanks as a wayto evaluate plumage variation in redpolls,which he treated as a single species. Thattreatment has not been followed by subsequentauthors, who treat Common and Hoaryas distinct species (Molau 1985, Knox 1988,Herremans 1990, Seutin et al. 1992, 1993,1995). Most authors indicate that differencesin streaking have some value when distinguishingthe generally less-streaked Hoaryfrom the more-streaked Common, but all authorswho discuss field identification cautionthat some individuals may not be identifiableto species or subspecies.Knox and Lowther (2000b), for instance,indicate that nominate Common Redpoll(Figure 2) usually shows “broad streaks onundertail coverts” and a “rump normally withextensive streaks; adult male [exilipes] HoaryRedpolls have at most 1-3 hairline streaks onlongest undertail coverts.” Also in exilipes,the flanks and breast tend to show less streaking(and generally finer streaks on average)than in nominate Common, and mantlefeathers and scapulars tend to be paler, as dothe edges of upperwing coverts and secondaries.Finally, the upperparts tend toward whiteand gray in Hoary, toward buffy and brown inCommon, though some exilipes Hoaries havebuffy tones in the head and back (Knox andLowther 2000b) and Hornemann’s frequentlyhave such tones (van den Berg et al. 2007).These general differences between thepalest, least streaked Hoary Redpolls and thedarkest, most heavily streaked Commons arehelpful when an observer is just gaining confidencein identifying redpolls to species. Asone begins to look carefully through largeflocks of redpolls, however, it becomes clearthat there are many birds that seem to be intermediatebetween the more stereotypicalCommon and Hoary and that differences inplumage appear to form a continuum, withsome individuals falling into a gray area notadequately treated in field guides. As Pittaway(1992, 2007) has emphasized, part ofthe reason for the extensive variation we observeis that each taxon shows plumage variationby age and sex—thus each has mini-V O L U M E 6 5 ( 2 0 1 1 ) • N U M B E R 2 207