>Why do coots bob their heads when they swim? Does it make them more
>efficient paddlers somehow?

This one is off the top of my head, but many birds do the same thing when
walking (even domestic poultry)! I have always assumed that it enables the
bird to keep its view of things steady until it jerks its head forward into
a new position, which may make it easier to discriminate movement against a
background - but it's just a guess. Ducks don't, I suspect, because they
swim much more smoothly than coots.

>
>Do swifts *really* sleep on the wing or is that just a rumor?

I believe that it was in a famous study of the European Swift by the late
David Lack (written up as "Swifts in a Tower" (1956), a classic of
ornithology, that it was first proposed that swifts sometimes spend the
night on the wing. This is now known to be true, and is made possible by
wing adaptations that permit them to fly slowly and expend energy at a low
rate. Whether the birds are sleeping is another matter - and is a
possibility for birds other than swifts. In the article on "sleep" in "A
Dictionary of Birds" (1985) it states:

"Evidence for sleeping on the wing is inevitably circumstantial as, for
example, the suggestion that the pelagic Sooty Tern Sterna fuscata may sleep
aerially since it quickly becomes waterlogged on the water's surface.
Rheinwald (1975) found that House Martins Delichon urbica descended to the
breeding colony early in the morning from great heights; he concluded that
they were unlikely to roost elsewhere than on the wing. Evidence from
eye-witnesses and from radar observations exists to suggest that Swifts Apus
apus can sleep on the wing, a view strongly supported by Lack (1956) and
others. Against this, it has been argued that the birds may descend after
observations cease and that radar identification is not unequivocal.
Certainly Swifts do also roost in their nest sites."
>
>When a hummingbird goes into torpor for the night, does it try to build a
>little nest or find an insulated crevice, to save as much heat as possible?

They certainly don't build special sleeping nests (I can't think of a bird
that does). Actually, not all hummingbirds go into torpor (Anna's
apparently does not). Some hummingbirds, like the Andean Hillstar that
lives at high elevations in the Andes where nights are extremely cold, will
find shelter in caves or abandoned mines, but many others simply sit on a
perch without any special attempt to find shelter. If you can find
"Hummingbirds: Their Life and Behavior" by the Tyrrells, a book your
students will enjoy for its superb photographs, read pp. 141-148 (much of
which is pictures, not text) for information about hummingbird torpor.
>
>Why does a nighthawk have combs on its claws?
>(Related note -- I believe the herons have a comb on their middle claw to
>comb powderdown into their plumage for improved waterproofing -- true? KH)

The fancy term here is a pectinate claw. From the Dictionary of Birds:
"After fouling the feathers of the head and neck with slime from their fish
prey (eels etc), bitterns and herons rub the affected parts on the
powder-down patches, then scratch off the slime and powder using the
pectinated claw, apply preen-oil, and then preen thoroughly." Many
non-passerine birds families have powder feathers, though they are not
always arranged in obvious patches as in herons. Unfortunately I have been
unable to find a reference on my bookshelf that tells me if nightjars have
them (though they all have pectinate claws). I would assume, though, that
the claw must be used to comb the feathers in some way.

I hope this helps!
--
Ronald I. Orenstein Phone: (905) 820-7886 (home)
International Wildlife Coalition Fax/Modem: (905) 569-0116 (home)
Home: 1825 Shady Creek Court Messages: (416) 368-4661
Mississauga, Ontario, Canada L5L 3W2 Internet: ornstn at inforamp.net
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Toronto, Ontario Canada M5H 3P5