Dennis Paulson wrote:
>
> >The bird that was seen at the feeder has not returned ....at least not while
> >I've been watching. But, I'll continue to make sure the feeder is full and
> >see if I can bring it back. (Paul Cozens-I'll let you know)
> >Dennis asked if I could elaborate........I'll try.....
> >I couldn't say that the bird was noticeably smaller than a house finch. My
> >impression was that it was about the same size. It was feeding a little
> (snip)
> >The tail was darker than a house finch. It was the whiteness of the head and
> >the bright red cap that was most attention grabbing. Legs were pinkish. The
> >bird was definetly shy. I got my binocs and crouched behind the sofa to look
> >at it. It saw the binocs peering over the back of the couch, stared for a
> >few seconds and took off. My friend saw it take off and said that the flight
> >pattern was very undulating.
> >Gosh, I hope it returns so I can verify my original impressions.
>
> >From Songbird's description, my parsimonious conclusion is that the bird in
> question was a partial albino House Finch. A redpoll really should look
> obviously smaller than a House Finch, and a Common Redpoll doesn't have a
> particularly white head. A lot of albinism affects only the melanin
> (brown, black) pigments on birds, so, for example, you can get a white
> Red-winged Blackbird that still has red epaulettes. A partial albino House
> Finch might have a red cap that would be much more apparent than that of a
> normal bird. The red color is distributed differently in the two species,
> but this might be subtle. A major difference would be that a House Finch
> would have a red rump, a redpoll a pale rump. Also, the House Finch has a
> rather heavy typical finch bill, the redpoll a slender bill for a finch.
>
> Dennis Paulson, Director phone 206-756-3798
> Slater Museum of Natural History fax 206-756-3352
> University of Puget Sound e-mail dpaulson at ups.edu
> Tacoma, WA 98416
> web site: http://www.ups.edu/biology/museum/museum.html

The "partial albinism" seems more likely to be due to pie-bald spotting
in which a white crown is usually a good sign. I have observed this
phenomenon in a bewick's wren giving the bird a full, blazing white cap
and white streaks down the wing.
Z. Thompson
zath at u.wahington.edu