One addendum to my previous post on Sandhill Cranes etc. in the Columbia
Basin.

I originally estimated the number of Cranes present at Scootenay Reservoir
as 3-4000. A very impressive sight. Then I counted the flock on the
ground by 20s, and came up with 1180, with a few more flying in. Still an
impressive sight, but another caution on estimating bird numbers when an
actual count could be done instead. I find that I almost always
UNDERestimate numbers by a factor of 2 or so, so the sandhill count was
particularly surprising. I've heard that one tends to overestimate
numbers of large birds and underestimate numbers in flocks of small birds;
perhaps that was operating here. Certainly the sight of several tons of
high-quality protein soaring overhead made an impact on my senses that was
qualitatively different from how I feel seeing 10,000 peeps or starlings
(as much as I love starlings).

Chris Hill
Everett, WA
cehill at u.washington.edu