In the East, I've watched "kettling" Broad-winged Hawks use thermal updrafts
to spiral upward in order to gain altitude and find the higher altitude
currents that can carry them long distances with little effort. I've seen
similar behavior by Turkey Vultures and Eagles. When birds see another bird
working a strong updraft, they all head for that invisible column of rising
air. It's called "kettling" because it resembles steam spiraling upward
from the spout of a boiling kettle. During fall migrations, raptors may
hunker down for days in the valleys, waiting for the right wind conditions.
But when one or two birds find a strong thermal, others converge on the same
thermal. It's pretty dramatic to see thousands of hawks "boiling" up out of
a valley to join a sea of hawks streaming overhead.
Gene Bullock
Poulsbo
----- Original Message -----
From: "Norma (Abby) E Larson" <larson8 at u.washington.edu>
To: <tweeters at u.washington.edu>
Sent: Saturday, September 29, 2007 9:03 AM
Subject: [Tweeters] Circling Ravens


>
> Hi Tweeters,
>
> Regarding Rob's sighting of circling ravens, I saw this in the Santa
> Monicas, near Encino, CA. Several hundred ravens soared in circles, (I
> counted at least 200) not too high up, calling occasionally to each other,
> and dive-bombing each other from time to time the way crows do. It lasted
> over an hour that day, and I saw them again the following day. I asked a
> local Auduboner about them, and they said there was probably a large
> carcass nearby. But for hundreds, just soaring, it felt to me like they
> were staging to go somewhere, or maybe it was just an Iron Man-type raven
> get-together. It was eerie. I'd sure like to hear more about this
> phenomenon.
>
> Abby Larson
> Seattle, WA
>
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