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From: deby@cs.utwente.nl (Rolf de By)
Newsgroups: rec.birds
Subject: Re: Confused migrant?
Message-ID: <9010131215.AA11006@utis15.cs.utwente.nl>
Date: 13 Oct 90 12:15:28 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 54


In article <1990Oct4.172011.1686@granite.cr.bull.com>
 horvath@granite.cr.bull.com (John Horvath) writes:

> I've heard that one common trap to migrants is flying into radio
> towers. The person who told me the story, claimed that the collisions
> were more frequent on foggy nights. I've tried to verify this story,
> but all the radio towers I could find, are enclosed in fenced in
> areas. ("Yes officer, I was just looking for some dead birds.")

Here in Europe (and especially in Denmark and Holland) one of the main
causes of death of migrating birds used to be lighthouses, and indeed,
mostly so during foggy nights in autumn. Apparently, in such nights
the birds start circling around the single light source that they can
find and eventually hit the walls somewhere.

The number of casualties has seen a dramatic decline from the moment the
lighthouses were put in footlights, so that now the birds could see the
whole building and not just its head.

On the same issue rmura@world.std.com (Ron Mura) wrote:

> I've known birders who do that, and also listen and can identify
> migrants by call.  One locally famous and well respected birder
> (he's high up in the Mass. Fish and Wildlife dept.) recorded 400
> migrating blue-gray gnatcatchers one night in Wellesley, Mass., in the
> 1960s.  The same fellow can supposedly identify birds flying in front
> on the full moon through his scope.

Sure, you can identify birds by their call, that is IF they call during
migration. Some species do, others don't. The Redwing (a eurasian thrush
that, I believe, is in the Nat. Geogr. guide) calls all the time, and
you can hear at least several hundreds during the night wherever you are;
the Fieldfare (a thrush also in that guide?) hardly ever calls during the
night.
I think not that many small passerines give contact calls when migrating
at night, and so I would be surprised if the Gnatcatcher does. Does it?

Identifying birds flying in front of the full moon through your scope
is ridiculous, I believe. OK, Cranes are allright, and so are Canada
Geese. But forget about all the smaller species. Either they passed
too quickly because they were too close, or they are too far anyway.
If you believe this guy could identify any of the parulidae in this
fashion, . . .

Rolf


Rolf A. de By
Vakgroep Informatiesystemen			Tel   : (0)53--893753
Faculteit der Informatica			b.g.g.: (0)53--893690
Universiteit Twente				Fax   : (0)53--339605
Postbus 217, 7500 AE Enschede			Email : deby@cs.utwente.nl
The Netherlands						deby@henut5.bitnet