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Re: bcf vs. badd



>Well.  How about this:  since these proto-birds were probably carnivorous,
>what if _they_ were the predators that some other poor creature was taking to
>the trees to escape from?  The proto-birds might follow them up (gradually
>becoming more and more adept at doing so, or perhaps, they already were
>adequately equipped).  The prey-critters, seeing that merely taking to the
>trees was not enough, might have taken to the jumping around in the branches
>hypothesised for the proto-birds as an escape mechanism.  The proto-birds
>then might have learned to fly/glide/whatever in order to catch these agile
>little critters, be they bugs, lizards, mammals or whatever.

>Derek Smith.
>

This is basically the same thing as saying that these critters evolved
arboreal habits and/or flight to assist in foraging, and as such does not
bother me.  But we should perhaps distinguish between flight as a method of
getting to where the food is (eg by flying from tree to tree, or branch to
branch) and as a method of prey capture.  The latter is clearly a lot more
difficult and requires special adaptations.  Looking at living birds we find
that flight as a prey-capture method can take several forms, such as:

Using flight to reach food in open water, as many seabirds do;

Flying from a perch to the ground or another branch to sieze a non-flying
prey item (the "sit-and-wait" strategy of such birds as kingfishers (many of
which are terrestrial), motmots, puffbirds etc;

Hovering in front of suitable foraging areas (outer branches etc) that
cannot be reached in any other way - this method is also used by some birds
such as trogons to collect fruit;

Aerial hunting followed by pouncing (as for many hawks);

Aerial pursuit and capture of flying prey (many falcons, flycatchers,
nightjars, swifts etc).

To my mind all these methods, with the possible exception of the second,
require special adaptations and modifications to the flight mechanism (eg
the ability to hover, or change direction rapidly) not to mention to vision,
neural function and many other  aspects of morphology.  As such I cannot see
them as proximate factors in the evolution of flight in the first place, as
flight must have been pretty rough-and-ready in the early stages.  Thus I
prefer (intellectually - I am not basing this on any fossil evidence) the
idea that flight first evolved to get from one spot (perch, etc) to another,
perhaps very close by and perhaps to nab a food item already spotted, but
not as a direct prey-capture method in itself.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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