[Tweeters] Northern Saw-whet Owls

J. Acker owler at sounddsl.com
Sat Nov 24 10:05:05 PST 2007


I just finished compiling my results of banding Northern Saw-whet Owls
(NSWO) on Bainbridge Island for the fall migration. While I saw a 50%
increase over the number I banded last year, my 18 birds is a paltry sum
compare to what the stations back east are seeing this fall. Prince Edward
Point Bird Observatory, in Ontario on a peninsula that juts into Lake
Ontario, banded over 1500. Whitefish Point, on Lake Superior in Michigan,
banded over 500 this summer and almost 300 this fall. Most other NSWO
banding stations in the east are experiencing record numbers of birds, some
with over 100 captures in a night.

The below is a paste from an email on SAWWHETNET that concerns the boreal
species invasion in the east:

"While this is anecdotal, birders throughout New
York, Vermont, and eastern Canada, are reporting unusually high counts
of many dispersing boreal species including Snow Buntings, Pine and
Evening Grosbeaks, Common Redpolls, Bohemian Waxwings, and others.
Furthermore, the Northern Shrike, a predatory passerine with a diet
similar to the NSWO, is also showing up in numbers.

According to the Ontario Field Ornithologists
ca/reports%20and%20articles/winterfinches.php), this
spring saw a huge boom in voles and field mice, followed by a poor
seed crop this summer. The seed crop failure has not only collapsed
the small mammal populations, it has caused birds to disperse wider
than usual to find food.

It would appear that the NSWO surge we're seeing now is the result of
very high fledgling survival rate due to this prey boom, followed by a
figurative escape from a region that is now lacking both rodents and
small birds."

J. Acker

Bainbridge Island, WA

Owler at sounddsl.com

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