Wednesday, March 5, 2008

A leucistic Pine Grosbeak

Earlier this week, I recieved some images of a strange canary-looking bird taken by Joe and Penny Bernard in Fort Fairfield. The bird has been coming to their yard for a while and they were only just recently able to get some pictures of it. It was a bit of a puzzler and not like anything I've seen in northern Maine before... exciting stuff for a bird nerd.

As you can see from Joe's picture, the medium sized bird was mostly white with some light yellow on the head, rump and breast and black and white on the wings. The beak and legs were pink. Unfortunately the bird was all alone, so there were no clues to its identity to be gotten from its associates...

There aren't too many species of birds that can reasonably be considered as candidates in Aroostook county in the winter...The closest looking normal-plumaged bird common in this area is probably the Snow Bunting. By comparing the Fort Fairfield bird to Paul Cyr's Snow Bunting photo in the previous post, you can see that this ID wasn't a good fit. Northern Shrikes have black wings and a lighter body, but they also have a black mask and a black tail which this bird didn't have. Young shrikes also have some brownish tint to some of the plumage but not the lemon-y yellow Joe's bird showed.

The only other birds with white, black and yellow plumage that came to mind were Evening Grosbeak and American Goldfinch. This bird was too big, mis-proportioned and way too light to be a goldfinch. All the white on the upper wing looked good for an aberrant plumaged Evening Grosbeak but the tail was too long....hmmm

On closer look, I found some clues to the birds identity. The bird looked like it had a thick, stubby beak. Medium sized birds with this kind of bill around northern Maine right now are Evening and Pine Grosbeaks and Northern Cardinals. As I said the long tail didn't work for Evening Grosbeaks, and the bird obviously didn't have the crest of a cardinal...Pine Grosbeak?

The shape/morphology was right, but the color? I got thinking about the yellow color. The head, breast and rump were yellow in the same places as a normally colored female/young male Pine Grosbeak. (See the bird in Paul Cyr's photo here) What appeared to be missing was the gray pigment that dominates the appearance of a female Pine Grosbeak. Missing pigment would also explain the beak and legs being pink rather than dark gray/black.

As I understand it, when birds appear to have reduced or partially missing dark pigments (melanin) most ornithologists call it leucism. For some reason the use of this term gets the hackles up on some people who prefer to call birds with lighter than normal plumage partial albino. I've used the term partial albino for such birds before, and had it explained to me that albinism is an all or nothing affair. Either the bird has two recessive genes and NO pigment(=albino), or not. A bird cannot be partially albino.

So, anyway... Joe's bird with some black and yellow pigments looked like it could be a leucistic Pine Grosbeak.

I hadn't heard of one before so I googled around for a while and found several references to such a bird. In our geographical area, there was one collected in Massachusetts in 1965 and a couple others reported in New Brunswick in the past five years. Most surprising was a photo of one taken just a couple of weeks ago (February 23rd) in Quispamsis, NB that looked alot like Joe's bird! This bird was decent enough to be photographed in the company of three other Pine Grosbeaks.

I sent the pics around to a few Maine bird experts and they all concurred with my suspicion that this was a very rare, leucistic Pine Grosbeak. Thats a really good find. Thanks for sharing it Joe and Penny!


Sandpiper said...

Very interesting post, Bill! My first impression without looking carefully was that it was a snow bunting. I would never have been able to figure out what it was. It really is pretty!

rita_poulton said...

I took a picture of a leucistic Pine Grosbeak in Northern Minnesota Sunday Feb 6, 2011. She was beautiful and flew in with a group of Pine Grosbeaks. I can share pictures if you wish.
Bemidji, MN