If anybody is interested...
I copied this from a website.
From: David La Puma <woodcreeper AT GMAIL.COM>
Date: Mon, 28 Nov 2011 12:02:19 -0500
As Sam pointed out last week, the southbound Snowy Owl irruption is
increasing daily across the northern US border. While there are a
number of sightings missing from the eBird map (not everyone uses
eBird... yet!), it still provides a very interesting overview (Nov-Dec
2011):
http://ebird.org/ebird/map/snoowl1?...&bmo=11&emo=12&yr=2011-2011&byr=2011&eyr=2011
(hint: toggle the year/month options to compare to other years)
During invasion years one of the first questions that comes to mind is
"what's causing the influx?". As Snowy Owls are tied to the cyclical
lemming population (as are Rough-legged Hawks) we can expect
irruptions during poor lemming years (not enough food to sustain them
through the winter) and in very good lemming years (plentiful prey
leads to high reproductive output of owls results in overcrowding on
the wintering grounds forcing more birds south). Several Arctic
biologists, being interviewed for an article on wintering raptors,
concluded that this was a very good year for most lemming populations
with "lemming population numbers close to historical highs in many
areas" (from Rob Fisher, IL. read his original post here:
http://www.freelists.org/post/wisbirdn/Lemmings-and-Snowy-Owls-no-sightings)
. Under such a scenario we would expect most of the birds heading
south to be juveniles as the adults should be more adept at defending
their wintering territories. That is the case with most of the birds
being found in Wisconsin at at least the one bird found in NJ this
winter (although I haven't investigated any of the other out-of-state
records). Aging and sexing Snowy Owls can be done in the field- but
does pose some challenges especially since we should always give the
bird enough room not to feel threatened. Kevin McGowan from the
Cornell Lab of Ornithology posted his take on the ID of such birds
back in 2001, here's the link:
http://www.birds.cornell.edu/crows/snowy.htm (thanks to Betsy Abert on
the WIBIRDN listserve for bringing it to my attention)
The Wisconsin eBird team is planning an article on the Snowy Owl
invasion for next week (they have had close to 20 individual birds
this winter), so if you're interested- check out their eBird page
here:
http://ebird.org/content/wi
in a week.
Weird, had lemmings on the mind a couple of weeks ago.
