Whoops, forgot the frame grabs.
On Thu, Nov 18, 2021 at 5:34 PM Robert O'Brien <baro@xxxxxxx> wrote:
I sent my brother in CA some of the White-throated Sparrow posts to OBOL.
Here is what he came up with. Very interesting.
The colors for low populations are barely visible so I've sorta causally
enhanced them. eBird lists no subspecies for White-throated Sparrow.
But I wonder whether, as he suggests, the west-of-the-rockies population
is isolated with respect to the Rockies/Cascades? Wonder if there are any
banding data?
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I've now spent some time looking at some species.
*https://ebird.org/science/status-and-trends
<https://ebird.org/science/status-and-trends>*
Enter species and then play. For step by step use the < & > keys at the
right.
One that is fascinating is the White-throated Sparrow. Massively an east
coast bird, but if you look carefully there's a California distribution
that winters in river valleys around San Francisco Bay and the Sacramento
and San Joaquin river areas.
But that's just part of the story.
If you watch the week-by-week distribution, the eastern U.S. birds not
only swarm into eastern Canada, but quite a large amount of them then head
west into Canada until they come to the Canadian Rockies in the west of
Alberta. Seemingly a barrier the eastern White-throateds don't breach.
Then the California contingent follows about exactly the same timing of
the eastern birds, but they go up the coastal route west of the Sierras and
Cascades into western British Columbia. (The Williamette is the major
route in your neck of the woods.) They then stay west of the mountains.
T'he populations seem to never mix.
Weird that's there this small branch of White-throated that is seemingly
cut off from their eastern cousins. Like the Scrub Jays in Florida.
Attachment:
WTSPfallmigration.jpg
Description: JPEG image
