Re: Sifaka and Chukar Behavior: Trees Down or Ground Up?

[Jeff Hecht <jeff@jeffhecht.com>]

At 12:47 AM -0800 1/23/03, Jaime A. Headden wrote:
>   So we now have two possible hypotheses for avian flight orgin, ground up
> supported by Ken Dial's experiments with galliforms, and trees down
> supported by Xu et al. on new (and not so new) fossils from the middle
> Cretaceous of Liaoning. [clipped]

From talking with Ken Dial when I was researching my New Scientist 
story, I don't know that his findings necessarily support the ground 
up theory. One point he made is that the little birds used their 
small wings to flutter back down to the ground after they climbed up 
an incline. In a more realistic environment, they could be running up 
a tree or bush, then fluttering back down. The little wings can't 
lift the birds off the ground, but they could help them come down 
gently.

If we extrapolate backwards and assume the ancestral forms had 
similar behavior -- and those are very BIG ifs -- that could mean 
flight evolved as a short-range behavior to get off the ground and 
then come back down quickly and efficiently. One thing nobody has 
mentioned is that some animals which climb up trees have a hard time 
getting back down, like the classic cat chased up a tree that has to 
be rescued because it can't get back down. THus wings could have 
evolved as a temporary escape mechanism that let the  proto-birds 
escape predators, then come back quickly when the predator was gone. 
-- Jeff Hecht


--
Jeff Hecht, science & technology writer
jeff@jeffhecht.com; http://www.jeffhecht.com
Boston Correspondent: New Scientist magazine
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