[Tweeters] Mt Rainier White Tailed Ptarmigan (Follow-up on winter
plumage bird in late July)
fsprucegrouse at yahoo.com
Tue Jul 30 22:24:05 PDT 2013
Here is a follow up on the oddly, plumage white tailed ptarmigan that Stefan Schlick and I found at Mt Rainier on July 27th. I got a general explanation from Dr. Schroeder but did a bit of research on the web.
Most likely, the bird is a female and it has remain in its winter plumage (basic) because of a hormonal imbalance. Based on an article written by Braun and Martin, it is suspected that the pituitary and thyroid glands failed to secret sufficient hormones to initiate replacement of white body feathers with normal breeding plumage. A bird normally molts into three different plumages in 8 months!
More details are provided in this 2001 article.
I only found three documented birds that had the same white plumage for late July. It is a rare occurrence based on Clait Braun's 35 years of experience with white tailed ptarmigans. Over 15,000 birds observed, only two females with this phenomenon were found at Mt Evans during his studies (1991 and 2000).
Also of note is another female, white bird found in late July of 2007 along the San Barbara Ridges (below Jicarita Peak) of New Mexico.
In addition to Stefan's excellent photos, I have posted a few different ones my website as well.
It was fun to find and study this winter, plumage bird in late July along with the small, newly hatched chicks within close range. At first, I thought the white, fancy alpine grouse was some kind of odd pigeon or mammal at a distance. I hope it survives and evades any potential predator by staying close to the snow fields!!
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