Wednesday, January 25, 2012

Common vs. Hoary Redpoll

Seventeen Hoary Redpolls were among the 5167 Common Redpolls I banded in Aberdeen, South Dakota (1979-2004; see previous post). Redpoll taxonomy is complex and poorly understood (Knox and Lowther 2000a, 2000b). Not only are Common Redpolls extremely variable, many, if not most, show overlapping characteristics with Hoary Redpolls. One reason for this variability is that six species of redpolls could exist, since the various populations of redpolls may not interbreed.

The photographs above are of extreme birds from northern Minnesota. The first photograph is of a Common Redpoll. Note its somewhat elongated, siskin-like bill, streaky flanks, and dark back. The second bird is a Hoary Redpoll. Note its overall frosty upperparts, relatively short, triangular bill, very lightly streaked flanks, and almost unstreaked undertail feathers.

Many other individual redpolls are not so easily separated into Common or Hoary redpolls. Erika, who has seen me band many intermediate birds, raises her eye-brow whenever I identify a Hoary Redpoll. This similarity apparently is not due to interbreeding, which, contrary to published reports, may be quite rare between the two species. Common Redpolls begin breeding before Hoary Redpolls. They also leave their breeding grounds earlier. The two species sometimes nest in different habitats and differ in call, physiology, behavior, and perhaps in diet (Knox and Lowther 2000a).


  1. Lovely photos. Wish they were all so distinctly different! I live in a place far enough south that I ought not see redpolls at all but this season I have a few regular visitors and I have been seeing them since early March. I do realize that the sighting of a Hoary would be highly unlikely, but at least one individual seems possible. I have been unable to get any decent photos as they seem quite timid. The physical differences seem subtle to say the least but you mention a difference in call. Can you explain that difference or direct me to a resource that can help?

  2. Try the Sibley app for your cell phone:

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  4. Ok thanks! I have IbirdPro and the sound recordings are different for the two. I think I hear the Hoary but my Sibley guide says they are "essentially identical." I will try the app. Thanks for the prompt response!