Hi Wayne & All,
Thanks for the suggestion, If that were the case, I suppose we should see
higher numbers on more northern CBCs (so far as they extend), and at more
northern eBird observation points (so far as they go).
Looking at eBird, observations farther north into Washington and British
Columbia still seem scant (apart from a couple of feeder-watchers who seem to
be reporting the same flocks of 15-30 birds repeatedly).
Perhaps elevational movement is part of the story. We have so few CBCs in the
mountains, and eBird coverage of mountain forests also becomes very scant in
winter.
Last evening, Paul Adamus mentioned to me that some Canadian biologists are
concerned about Evening Grosbeaks, in part due to their tendency to forage for
grit along gravel roads, and then be killed by passing trucks.
The CBC database does show a steep decline for this species in western regions
(about 8% per year in the Northern Pacific Rainforest region, and 9% per year
in the Great Basin). That could perhaps be accounted for, in part, by Evening
Grosbeaks staying longer farther north or at higher elevations where there is
less CBC coverage. I don't know whether or how the CBC analysts have weighted
geographic coverage in their analysis. But taken at face value, those are
worrisome trends.
Joel
From: "Wayne Hoffman" <whoffman@xxxxxxxx>
To: "clearwater" <clearwater@xxxxxxxx>, obol@xxxxxxxxxxxxx
Sent: Sunday, January 6, 2019 5:19:52 AM
Subject: Re: [obol] Evening Grosbeaks
Hi-
My first thought is maybe they are staying farther north, longer into the
winter?
Wayne
On 1/6/2019 12:37:19 AM, clearwater@xxxxxxxx <clearwater@xxxxxxxx> wrote:
Today's lonely Evening Grosbeak got me wondering ...
I haven't seen all of the numbers from this winter's CBCs yet, but the pattern
of very low Evening Grosbeak numbers in the past two winters seems to be
continuing into this winter.
In 2016-17 only 3 (three) were recorded on CBCs, in total, statewide.
In 2017-18 numbers were up a bit with a total of 41 on Oregon CBCs, but only 2
in the Willamette Valley, and only 5 on coastal CBCs.
I did look at eBird and it gives no real clues. If you add up all of the
reports from the western U.S. and Canada in this winter and last, I doubt it
would add up to a tenth of what you could find on the Oregon State campus on an
average day in April. Here and there you might find a report of 15 or 25 birds,
but most reports are of singles or a handful of birds. Certainly nothing like
the flocks of 100+ that I remember encountering at the Summer Lake Rest Area in
winter 10-15 years ago.
Any ideas?
--
Joel Geier
Camp Adair area north of Corvallis
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