Jan 28 2008

Counting Crows

Published by at 12:15 pm under Crows & Ravens,Migration

Crow roost at dawn (photo by Doug Bauman) Last Friday outside my office window I noticed a steady stream of crows flying west-northwest into Oakland.  They were coming in to roost.

I went back to the task at my desk but when I looked up again the stream was still there, still steady.  Amazing.

I usually don't try counting crows because I lose track but I remembered Dr. Tony Bledsoe telling me how he estimates flock numbers by counting the rate of birds during a given period of time, then measuring the time.

I picked a point of reference and set my stopwatch.  200 crows per minute.  Now all I had to do was watch until the stream ended and check the rate of crows periodically.

I watched until it was too dark to see them.  I checked the rate a couple of times and they still flew in at 200 crows per minute.  Even after dark they kept coming, though the rate seemed to drop, but at that point I couldn't be sure because they matched the sky.

From start to end, it was 70 minutes.  14,000 crows.  And those were only the crows I could see!  Judging by reports of crows elsewhere in Pittsburgh, the total number could be two or three times that.

In about a month, the flock will begin to disperse.  In the past few weeks they've changed their start and end points, and anyone who thinks "as the crows flies" means a straight line ought to watch this flock.  Even their flight path curves in the sky.

What a spectacle!  I've been to Nebraska to see sandhill crane migration and to Middle Creek to see snow geese.  Crows aren't as "nice" as cranes and geese but they put on just as big a show.

           The photo is a Pittsburgh crow roost at dawn by Doug Bauman.

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