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Re: Archaeopteryx with bird book, was Re: Archaeopteryx flight



Patrick Norton (ptnorton@suscom-maine.net) 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.>

  Perhaps still three. Most ciconiiforms are feather-heads, rather than bald.
Storks, among herons and ibises, tend towards bald faces, but a complete bald
head is known in a few species, as well as the bald ibis (*Geronticus*), and
among storks specifically we have a clade of leptoptiline ciconiid storks
including the jabiru (the latter -- *Jabiru* -- a close ally of the marabou,
*Leptoptilos*, and they have at times been synonymized), with *Ciconia* and
*Anastomus* having a fully-feathered head and *Mycteria* having a half-bald
face, less bald than the bald ibis. In addition, the sister taxon to the storks
("Ciconiida") are the New World vultures, "Vultures", which tend to have either
fully-feathered heads or at most a bald head, but unlike the Old World vultures
lack a fully-bald neck. They also tend to have wattles, as in the ciconiids.
This, as with other ciconiiforms, as well as the colors, may indicate a display
function for the brightly colored, patterned, and wattled faces of marabou,
jabiru, other storks and vultures. The Old World vultures, many with fully
feathered heads like the lammergeier (specializing in cracking bones open, not
corpse feeding), tend to be less elaborately colorful unless its in the
feathers alone, with pinkish or reddish heads and necks. Thus said, there are
likely other reasons for having a feather-less head than for dumpster diving,
so to speak.

<Secondly, the life-style of scavengers like vultures is very specialized.>

  Only for some vultures, not all. Many, as noted above with the lammergeier,
make do with bones, others specialize in outer viscera and others for far
deeper, and others specialize in hide alone, while more specialize in smaller
versus larger carcasses or even hunting, so the vulture clan are not always as
"unclean" as they might seem :)

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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