[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Altitude effects on hummingbird flight?
----- Original Message ----
From: Dann Pigdon <email@example.com>
To: DML <firstname.lastname@example.org>
Sent: Thursday, December 21, 2006 6:16:03 PM
Subject: Re: Altitude effects on hummingbird flight?
don ohmes writes:
> Hummingbirds are the largest observed species using hovering, a
> size-constrained locomotion; if some "un-related" group of similar size
> evolved hovering, it seems to me that a high degree of convergence
> would be expected. In either case, I wonder what could have knocked
> them out? Given that hummers occur in Alaska, it astonishes me that
> they never got a foothold in Asia. Anybody know got a clue?
Some (many?) extant hummingbirds seem to be highly specialist feeders,
sometimes only feeding from a very limited number of flower species. Often
those flower species themselves mostly get pollinated by hummers alone. If
one species is reduced in number then the other may follow (if one or the
other can't adapt to a new food source / pollinator). I can very easily
envisage a feed-back spiral driving both into extinction in times of
The question really isn't why hummers from other parts of the world may have
become extinct; perhaps the more interesting question is why such highly
specialised species have managed to survive (and even thrive) in the
Americas for so long. Specialists generally don't do so well during
---------------- Good points, although there are a lot of willing
pollinators around here (FL). I like Tyrberg's second hypothesis best for
explaining the lack of re-invasion across the Bering Strait. Any hummer
that happened to cross the Bering Strait in the summer
certainly would be in big trouble if it tried to 'home in' on its'
winter grounds in the Fall. If I had thought of that, I never would have raised
the issue. Of course, that doesn't attempt to explain the initial
disappearance from Eurasia.
GIS / Archaeologist http://www.geocities.com/dannsdinosaurs
Melbourne, Australia http://heretichides.soffiles.com