>I've heard of a hypothesis that proposed that the light colored tail
>spots and markings on warblers (and other migrants) might be used by
>the birds to follow each other in the night--kind of like tail lights on
>a car. This would of course be dependent on flocking behavior. Is this
>a crazy idea? In any case, isn't it interesting that so many migrants
>have light colored spots on their tails?---other ideas?
>
>--
>David Bailey, psu03321 at odin.cc.pdx.edu

I have the feeling that it's too dark for this to work, David, and I would
probably question why vireos, thrushes, sparrows and most other nocturnal
migrants didn't have such convenient tail lights. And, of course, many
warblers lack them too. Tail markings on many birds--vesper sparrows,
juncos, meadowlarks--almost surely are diurnal signals of flight, so
perhaps warbler tail markings are too, but they are somewhat different.

I certainly think that the yellow rump on a yellow-rump is a
flight/flocking signal, appropriate for such a gregarious warbler. I think
the big tail markings in redstarts, and possibly other birds, are exposed
to startle insects into moving.

My big question is about the source of the hypothesis. I'm very interested
in bird coloration, and that's a new one for me.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416