Tuesday, December 4, 2007

Redpoll subspecies

If identifying Hoary Redpoll is not enough of a challenge for you, maybe you'd like to look for subspecies of Hoary and Common Redpolls?

First, check out this map from the Canadian Atlas of Bird Banding.

This shows selected western band recoveries of Common Redpolls, and the obvious suggestion is that some of the Common Redpolls being seen in the east right now might be coming from Alaska! Troy (1983) shows a map with a similar pattern, including a redpoll that traveled from New Hampshire to Barrow, Alaska, and another that traveled from Michigan to Siberia. Lots of redpolls also come to the eastern US from the north or northeast, but we should not assume that we are only seeing redpolls from the nearby subarctic regions.

Both species of redpoll are represented in Greenland and Baffin Island by larger and more distinctive subspecies. These "Greenland" Hoary Redpolls are large and very pale, while the "Greenland" Common Redpolls are large and dark. An excellent summary of status and identification is in Pittaway (1992). Greater Common Redpoll can appear in the eastern US in significant numbers some winters, outnumbering Hoary (Pittaway 1992, Wetherbee 1937). Hornemann's Hoary Redpoll is the rarest subspecies in the US, but has been recorded at least south to Maryland and west to Michigan.

Common Redpoll Carduelis flammea
Southern C. f. flammea
Greenland (Greater) C. f. rostrata

Greater is distinguished from Southern by:

  • larger size
  • darker color
  • larger bill with curved (bulging) culmen
  • said to have more upright posture and harsher calls
Hoary Redpoll Carduelis hornemanni

Southern C. h. exilipes
Greenland (Hornemann's) C. h. hornemanni

Hornemann's is distinguished from Southern by:
  • larger size
  • even paler color
Some photos and discussion of Greater Common Redpolls from Toronto already this winter are available here. And a detailed discussion with photos of specimens by the Maryland/District of Columbia Records Commmittee is here (beginning on page 16).

Other references:
Pittaway, R. 1992. Recognizable Forms: Redpolls. Ontario Birds 10(3): 108-114

Troy, D. M. 1983. Recaptures of Redpolls: Movements of an Irruptive species. J. Field Ornithol., 54: 146-151.

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