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Re: Archaeopteryx with bird book, was Re: Archaeopteryx flight
Patrick Norton wrote:
Although the old and new world vultures are veiwed as not sharing recent
common ancestors, the new world vultures are viewed as arising from the
stork lineage (see Sibley and Alquist, 1990). So this narrows the list to
two taxa of bald headed scavengeres, at most.
I'm not so sure that the link between New World vultures (Cathartidae) and
storks (Ciconiidae) still has much support these days. See, for example,
the morphological analysis of Mayr and Clarke (2003), which has cathartids
The feeding behavior of vultures is in large part a function of their size.
If you are a big avian scavenger, you can't physically enter into the body
cavity of most dead animals, so, by necessity, you have to insert your
This is partly true. But if the carcass is much bigger than the scavanger
then this also necessitates the scavenger inserting its head and neck deep
into the carcass. This is frequently the case with vultures when feeding on
the carcasses of pachyderms and large ungulates - especially after all the
best bits had been taken by those carnivores higher up in the pecking order.
But small scavengers (like corvids---and Archie, by the way) are/were able
to hop inside a rib cage of a relatively small animal without much problem.
>This is well documented, and I have personally flushed several scavenging
ravens from deep inside the chest cavity of a coyote.
I think this is apples and oranges. Some vultures cannot actually access a
fresh carcass by themselves - their beaks and talons are incapable of
ripping open the hide of large mammals. So, this means they either have to
access the innards via available orifices (mouth, anus), or wait for another
carnivore to tear open the hide (like a lion or hyena). In any case,
getting inside a carcass is not always so easy for a vulture or marabou. I
would guess that it is much easier for a raven to get inside a dead coyote
than a vulture to get inside a dead wildebeest or elephant.
The thing that bugs me about the often-stated idea that bald heads in birds
are somehow a preferred adaptation for a scavenging lifestyle is that there
isn't a shred of evidence to support it. One, maybe two, taxa of large
avian scavengers are bald, but the large majority of avians who scavenge
for a living are not.
But many vulture species are actually highly specialized for scavenging.
Sure, some vultures also kill their own prey (small prey), but vultures have
a specialized strategy for feeding off carcasses, and their morphology
reflects that. I think there is good evidence that the naked head and neck
is an adaptation to a particular type of scavenging, not just being a
scavenger per se.