Friday, April 17, 2009

Migration: Yes and No

Radar is showing birds are moving across the eastern U.S. tonight, as of 11:45 EDT, but you wouldn't know it standing outside our place. All I hear is Tupac. Or Notorious B.I.G. Or Snoop Dog . . . ah, hell, I can't tell my west side from my east side.

We've got mild temperatures, no real breeze to speak of, clear skies, and not a prayer of hearing a flight call.

Continental base reflectivity shows a good movement
occurring from the Mississippi River east to the Atlantic coast.

Kenn Kaufman articulates what I think we'll wind up with here in the Southern Tier of NY this weekend: the departure of some of our wintering birds, such as Dark-eyed Juncos, and an influx of short-distance migrants. We're still a couple weeks from neotropical birds dripping from the trees, but hopefully this weekend we'll see newly-arrived sparrows, Hermit Thrushes, Yellow-rumped Warblers and the like.

I find this image interesting:

Base velocity from Binghamton, NY, 11:45 PM EDT.

This is base velocity, not reflectivity, meaning it shows movement rather than mass. The orange-red-yellows are moving away from the radar station, the blue-greens are moving towards it. The gray is essentially neutral, so if you follow the gray area you create a line perpendicular to the movement.

Another way of saying that: draw an arrow from the blue-greens pointing towards the red-oranges, that's the direction the birds are moving.

This image shows the movement primarily to the east, slightly northeast, not the due north you'd expect. They are called northbound migrants, not eastbound, after all. But take into account winds, which have been coming out of the west and northwest all day, likely affecting the direction the birds move.

Tomorrow should hold some new birds, assuming my neighbors crash sometime before dawn. Or at least turn off the stereo.


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