The recent puzzle of the mass mortality of bank swallows on a road reminded me
of an article I found while researching merlin behavior. It's called "Merlin
feeding on road-kills", by Elizabeth Haug, and appeared in Raptor Research 19
(2/3):103. She says

"In late April, 1979, .... while driving along a paved secondary road, at
approximately 1000 H, I observed 20-30 dead or crippled Purple Martin (Progne
subis) in a tight group on the road. They had apparently been attracted to
radiated heat from the paved surface, a behavior previously documented for
several bird species (Whitaker, L.M., Wilson bulletin 72:403-404, 1960) and had
been run over by a vehicle."

She goes on to describe her observation of a merlin feeding on the crippled (not
the dead) martins.

So add radiated heat to the theories.

Chris Maack
Bird Treatment & Learning Center
Anchorage, AK
73201.3124 at compuserve.com