Joan,
Interesting suggestion. From an engineering perspective I have doubts that
the low specific heat of the plastic and the low thermal conductivity of the
plastic would support any appreciable heat transfer out of the birds feet; I
don't believe that the "draining heat" mechanism is supported by the physics
of the situation. (I might agree if it were an aluminum perch like on a
Droll Yankee seed feeder). However, another possibility is behavioral.
Since hummingbirds generally feed while flying the relative inactivity of
sitting in the early morning could lower metabolic rate. Coupled with
sipping on an unlimited (as far as the tiny bird is concerned) supply of
cold liquid could induce hypothermia. One would expect that a natural "I'm
cold" reflexive response would get the bird flying, thereby raising the
metabolic rate, but who knows. I was glad when my rewarming technique
seemed to work and the bird flew away. Do pass along the article if you
find it.

Thanks

Charles Vaughan
CEVaughan at aol.com
Woodinville, WA

>Hi! I was just perusing some mail I'd kept and remembered I'd meant to
>respond to your tweeters note about the rufous hummingbird you'd found
>clinging upside down from a perch on your hb feeder.
>
>Some time ago, I read that feeders with perches caused hypothermia easily in
>hummingbirds because contact with the perch drained bodyheat, especially in
>early morning temperatures. Thus the recommendation was to use hb feeders
>*without* perches. If I can ever figure uot where the article is, I'll pass
>any pertinent info along.
>
>Regards,
>Joan Inkster-Smith
>(jinkster at netshop.net)
>Kamloops, B. C. Canada
>
>
>