Re: Possible Swainson's Thrush in Berkeley
Fri, 22 Mar 2002 15:07:46 -0800
From: Tom Condit
Allen Fish wrote (off the list):
I noticed a group of Hermit Thrushes and American Robins performing exactly the behavior you described in an English ivy vine two days ago on Buena Vista Way just below La Loma. They were so berry-crazed that the Hermit Thrush stood within two feet of me and my toddler son for a good two minutes. I'll ask around on the Purple Finch thing; maybe this is an unusual boom year
After poring over many an ancient volume of forgotten lore, I'm pretty sure the bird was a Hermit Thrush after all. The spots were too big and distinct to be a Swainson's Thrush. What it looked most like is what Sibley calls the "interior western" form of Hermit Thrush - very little red. What really got me meandering was that at first glance the bird's face had a distinctive light-colored pattern, almost like a White-breasted Nuthatch.
Tom
P S. There was indeed a young American Robin in the same ivy vine, just sitting in the center and gorging itself. (I say "young" because the breast was very light-colored.)
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Still more on pigmentation terminology
Fri, 22 Mar 2002 16:56:27 -0800
From: Don Lewis
If you want to be further confused, take a look in Birder's Dictionary by Randall Cox (1996). He uses the same definitions as Larry Tunstall did today for total, incomplete, etc., albinism but for leucism he says "a condition of paleness of plumage due to environmental factors instead of genetic abnormality."
Seems like a good idea to stop using leucistic, even though I did use it just yesterday talking about a Turkey Vulture with a white primary or two.
Don Lewis
Lafayette, CA
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Re: Possible Swainson's Thrush in Berkeley
Fri, 22 Mar 2002 17:12:14 -0800
From: Lisa Viani
These Hermit Thrushes seem to be quite variable. (Remember, I was the one who thought I had an Ovenbird a few weeks ago!)
Best, Lisa Viani
Richmond
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Hermit Thrush variability
Fri, 22 Mar 2002 18:54:34 -0800
From: Rusty Scalf
Several years ago I was hiking through the Schulman Grove of ancient Bristlecone Pine in the White Mountains (Inyo County), and came upon a singing Hermit Thrush that was basically gray in color, with just a little brown rust on the tail and primaries. I was astonished. Turns out some of the Basin and Range Hermit Thrushes look quite different from the ones that winter on our coast. I don't know where this interior population winters or if they ever occur in coastal California.
For a long time I have been impressed with how variable our winter Hermit Thrushes are; Ranging from quite spotted on the breast to virtually no spotting at all, just some amorphous brown smudging at the throat. Perhaps the latter birds are young ones. Does anyone know? Back color seems variable as well, with some having an almost greenish hue.
Rusty Scalf
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Re: Hermit Thrush variability
Fri, 22 Mar 2002 19:21:49 -0800
From: Mark Eaton
Yes, the Hermit Thrush population from the interior, Catharus guttatus auduboni, can be quite pale and difficult to identify based solely on coloration. This winter, we had a bird in Nayarit, Mexico, that we looked at for quite awhile before we realized that it was indeed a Hermit Thrush, most likely auduboni. Range maps also indicate a significant wintering population in Mexico, though I haven't seen one that separates out the subspecies' winter ranges.
Mark
Mark Eaton
San Francisco Field Ornithologists Web Site http://www.sffo.org/
SFBirds mailing list http://groups.yahoo.com/group/SFBirds
Personal Home Page http://home.pacbell.net/mweaton
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