Re: About migration
Wed, 21 Apr 2004 12:46:20
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From: Les Chibana
Steve Glover had great info on the Fox Sparrow in answer to that part of Phila's question. One small point about the Golden-crowned Sparrow: They aren't sexually dimorphic in plumage, so I don't think you can determine the sex of one by plumage. Both males and females are looking awfully spiffy these days!
The evolution of bird migration is an interesting subject. I am not well-read enough on it but can suggest that local sparrows are probably appearing in response to seasonal cycles of seed production, insect abundance and fruiting plants. These food resources have developed over the long-term partly in response to climate. Or, were introduced. Someone on the list may have more accurate botanical info that can shed light this point.
I think the Canada Goose flocks that seem to be resident come from re-introduced individuals rather than migrants who decided that they no longer needed the air miles. Perhaps someone has done the research and put out a paper on the subject. The only other birds that I can recall reading about that seemed to stop migrating were the Trumpeter Swans in the Yellowstone(?) area, but I think they were captive bred and were being reintroduced into the wild. In their case, the ready availability of grain put out by the people managing the reintroduction was thought to cause the birds to winter in the area. I don't think the birds had a well-developed sense of migration because of their human upbringing. It would be interesting to know about birds that were not captive bred, or introduced, that stopped migrating.
In an opposite kind of situation, I've heard that reindeer introduced to the Seward Peninsula in Alaska for the Eskimo people to have as a range herd have been linking up with the wild barren ground caribou herds that migrate to that region. As a result, the reindeer have been leaving with the caribou. By the way, these are the same species, Rangifer tarandus, and are not really differentiated to a subspecies level. "Reindeer" is the European name and these are all domesticated.
Les Chibana, Palo Alto CA
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Re: About migration
Wed, 21 Apr 2004 13:07:41
-0700 (GMT-07:00)
From: Rusty Scalf
It would be interesting to know if the Swainson's Hawks which now winter in the Delta in significant numbers are local birds, or birds wintering from farther north. The Delta is a long ways from Patagonia, Argentina! When I was a kid there was not a single accepted winter record for this species in California.
Rusty Scalf
Berkeley
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Arrowhead Marsh, Oakland
Wed, 21 Apr 2004
14:44:07 -0700
From: Courtenay Peddle
Hello folks,
of particular note on a drizzly Wednesday at Arrowhead Marsh (Martin Luther King Jr Regional Shoreline, Oakland) were a single Black Skimmer and, at noon, a Merlin that perched in the dead snag for us to enjoy.
Here's the complete list:
Good birding!
Courtenay Peddle
Re: Winter stragglers
Wed, 21 Apr 2004 15:32:25
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From: Frano
I as well watched a beautiful Golden-crowned Sparrow in my yard here in Hayward yesterday. He was in hot pursuit of a female, and his head was a jet black with a bright yellow stripe. It is the first I have had here this late. The White-crowned Sparrows are enjoying my feeder as well.
Frano
Hayward
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To every season...
Wed, 21 Apr 2004 18:31:59
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From: Joy Maxion
Continuing the migration thread... It is a transition time indeed, waiting for the summer arrivals and saying goodbye to the winter birds. The Dark-eyed Juncos, White-crowned Sparrows, Hermit Thrushes and Fox Sparrow have departed from my yard. I also had 2 beautiful Golden-crowned Sparrows yesterday, but I have not seen them today. I only saw them in my yard one other time this season, early in the winter, so it was a treat to see them again. The Bewick's Wren and Chestnut-backed Chickadee are setting up in the nest boxes and I saw 2 juvenile Mourning Doves today. I think I have been hearing the call of a Pacific-slope Flycatcher, but I have yet to find it.... Yes indeed, summer with its Black-headed Grosbeaks, Hooded Orioles and other brightly colored birds, is just around the corner....
Joy Maxion
Sheffield Village, Oakland
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Re: Strange yardfellows
Wed, 21 Apr 2004 20:28:43
-0800
From: Douglas Vaughan
The planets must be aligned. For the second time this "winter," we had our two White-throated Sparrows simultaneously this morning (and I thought, but won't swear, that I heard one singing yesterday morning). At least one of these has been present since mid-December.
Doug Vaughan
Berkeley
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