[obol] Re: Question on Pine Grosbeaks
- From: Joel Geier <joel.geier@xxxxxxxx>
- To: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
- Date: Sat, 14 Mar 2015 17:30:55 -0700
Hi all,
I tend to agree with Bob Archer's thoughts, that Pine Grosbeaks are
regular in the Cascades in winter, but this winter's unusual access has
resulted in finding higher numbers.
In past winters (at least during my previous stint as a local/regional
field notes compiler), it was not unusual to get a few reports of small
flocks of Pine Grosbeaks from X-c skiers who went out on the trails in
winter.
It seems reasonable to view the higher numbers this winter as a function
of better access. If you plot up all of the reports (including those who
looked but didn't find any), there are only a few reports of more than
20 birds, and many more reports of smaller flocks that are in line with
the kinds of numbers that ski-birders have reported in past winters.
Plus many reports (and unknown numbers of non-reports) from birders who
looked but didn't find any Pine Grosbeaks.
Perhaps one could get a better profile of the frequency of detections by
looking on eBird, though "motivational censoring" of data has to be
significant (Just a thought experiment: if you drive up to Santiam Pass
and only find a couple of ravens flying around, are you more or less
likely to take the time to go online and punch in your list, than if you
also saw your first Linn Co. flock of Pine Grosbeaks or your first Am.
Three-toed Woodpeckers for 2015?).
These types of sampling bias are very difficult to suss out, even with
fancy mathematics, so I expect that if we just look at eBird, we'll be
left in the realm of speculation.
What's unusual about this winter is that three Pine Grosbeaks were found
on Marys Peak in early winter, and recently six were photographed by
Bill Proebsting at low elevation in Corvallis. Those extralimital
occurrences seem to point to an irruption.
Good birding,
Joel
--
Joel Geier
Camp Adair area north of Corvallis
OBOL archives: www.freelists.org/archive/obol
Manage your account or unsubscribe: //www.freelists.org/list/obol
Contact moderators: obol-moderators@xxxxxxxxxxxxx
Other related posts:
