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November 2007

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From:
Tom Bain <[log in to unmask]>
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Date:
Wed, 7 Nov 2007 08:46:47 -0500
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Early this morning I looked through a cloud of 60 to 70 goldfinches (plus
two Pine Siskins) fussing over perch-space on my four tube feeders, and
behind them, in the distance, the local cell tower was hosting thirteen
Black Vultures on roost. The last bird left the tower at 7:36 AM this
morning.

Backstory: Vultures have used the new tower (built maybe five years ago)
intermittently through the autumn this year, but only in two's and three's
until now. If previous years' patterns prevail, numbers of roosting birds
will increase rapidly during the coming weeks and will fill all available
perches--about fifty birds can find space on the tower. I've observed as
many as 80 birds buzzing the tower looking for a perch at one time (two
years ago).

Last winter, early on, the roost moved, every last bird, a couple miles west
onto a large electricity transmission tower in Paint Creek Valley (US Route
50 west of Chillicothe), before it grew so large. The transmission tower
holds many more birds, and the Black Vulture population is growing annually.

I have a Black Vulture nest in the Ohio Breeding Bird Atlas II block that
includes this tower (I had none in the area during the first Atlas).

Peterjohn (The Birds of Ohio, 2001) suggests Black Vultures have been
increasing in Ohio through the 1990's. I'm sure they continue to increase in
the 21st Century. Black Vultures are a southern species near the northern
limits of their mid-western range in Ohio.

A Harbinger of global warming?

Have fun with using Christmas Bird Count data to make a long-term graph of
Black Vulture Population growth here:
http://audubon2.org/cbchist/table.html


Tom Bain
The Glaciated Allegheny Plateau
Ross County

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