Thursday, December 14, 2006

And they're off---but can migration re-wind?

Well, today is the official beginning of our favorite time of year--Christmas Bird Count season. There don't appear to be any Chicago-area counts scheduled for today, but there are a few downstate counts taking place, and today is the beginning of "Count Week" for some of the big Chicago-area CBCs.

Here's the big question facing all of the counts that will take place this weekend in this part of the Midwest: will the unseasonably warm weather (one forecaster predicts 60 degrees on Saturday in parts of northern Illinois) help or hurt the count totals? Last weekend almost every non-moving body of water in the Chicago area (away from Lake Michigan, of course) was frozen solid. Most moving water (rivers, streams, even the tiniest creeks) seemed to still be open. There was also a pretty tough layer of snow and ice everywhere; those conditions seemed ot really concentrate landbirds last weekend along areas of open or running water.

This weekend, all of those lakes and sloughs should un-freeze; marshes along rivers will almost certainly be open, and fields and prairies will be wet: free of snow and ice, with possible habitat for snipe and who knows what else. So, will we see empty prairies and and sloughs this weekend, or will those areas fill up with birds that headed a south a week or two ago when everything froze? We have this working theory that ducks (and for that matter all birds) try to stay as far north in their range as their specified habitat allows, so they can get back to their breeding grounds in the spring as soon as possible. So puddle ducks would stay as far north as they can to find the particular kind of water resource that they need to feed. Is that true? Can micro-weather conditions of a limited duration prompt migration to re-wind to where it was two or even three weeks ago, thereby giving us some birds that woud normally only be seen in late November and not in late December? We have no freakin' idea, but it will be a fun hypothesis to test out!

So good luck and good birding to all of the folks doing the FermiLab, McHenry, Lisle/Arboretum, and Chicago Urban counts this weekend, and to everyone around the world who is doing their 1st or their 100th count this weekend.

1 comment:

Bill Pulliam said...

I've long wondered whether the ducks in eastern N America really do stay just south of the freeze line, or if they in fact head straight down to the gulf coast for the duration once the freezing weather first hits the midwest.

70F in middle Tennessee this weekend, after single digits just a little more than a week ago.