[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: more evolution of flight



 Colette H. Adams <cadams@hh.gpz.org> wrote:
> I have to say I am not impressed with scenarios that have these
protobirds
> using their forelimb feathers to help them catch prey.  I have seen
> mockingbirds using their wings to apparently scare up insects, but modern
> birds do not have forelimb claws (with few exceptions), and I just cannot
> envision long feathers evolving strictly for the purpose of prey
> acquisition in an animal that already has well-developed forelimb claws. 

No one subscribes to the "insect net" explanation for (the proposed
ground-dwelling theropod) "Proavis" forelimb feather development any more,
so far as I know.  John Ostrom originated this hypothesis, but later
rejected it.  A net utilizes a multitude of holes to enable it to be
swiftly swung through the air without air resistance slowing it down, and
Larry Martin pointed out that a multitude of holes is essential to net
function, for without the holes, the sudden rush of air (from the "nets"
smacking together) would otherwise blow the insect prey right out of the
trap.  As avian wing feathers do not provide such holes, this absence of
holes would pose a serious problem to the hypothesis, as the proposal does
not provide a satisfactory selection pressure for the evolution of avian
flight feathers as we know them.  Pat Shipman's book, _Taking Wing_,
touches on this issue.   

-- Ralph Miller III     gbabcock@best.com