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RE: Microraptor also ate fish
Tim Williams wrote-
> > I never said Microraptor couldn't or didn't hunt, just that no food item in
> > its stomach could ever
> > support this over scavenging in any particular case. Thus no ingested food
> > item could support
> > a particular behavior for Microraptor, be it climbing or catching fish.
> An ingested food item can corroborate an ecomorphogical hypothesis.
> _Microraptor_ has been interpreted as a climbing animal. When an
> arboreal bird turned up in its abdominal cavity, this discovery was
> consistent with that interpretation. The discovery of fish remains is
> consistent with _Microraptor_ hunting aquatic prey as well. I think
> this interpretation is more parsimonious than scavenging, based on the
> behavior of many modern predatory mammals and birds.
Consistency does not equal corroboration when there is an alternative the
evidence is equally consistent with.
You would have to demonstrate hunting is more parsimonious in both cases, and
that hunting arboreal birds in trees is more parsimonious than doing so on the
ground in the first case. My cats have caught their share of arboreal birds
(mostly juncos, robins and starlings) in my life, and every time I've seen it,
the bird's been on the ground. Certainly doesn't seem rare enough to catch
arboreal birds on the ground that we should consider it unparsimonious for
fossil carnivores. Similarly, I have observed gulls feed on fish carcasses at
the beach. Exactly what behavior do you have in mind that makes scavenging
unparsimonious, as the whole Tyrannosaurus predator vs. scavenger debate
basically established any (non-vulture) terrestrial tetrapod predator both
hunts and scavenges?
> > Enants and Confuciusornis have similar pedal claw angles (Glen and Bennett,
> > 2007), which
> > could equally fall into ground-dwelling or perching birds (Pike and
> > Maitland, 2004- fig. 4).
> Enantiornitheans typically have superb perching adaptations, including
> a hallux that was large and fully descended. This argues against them
> being ground-dwelling birds -
> on the ground. _Confuciusornis_ has a shorter and elevated hallux.
> (The degree of caudal/posterior orientation of the hallux may have
> been comparable, depending on the enantiornithean in question.) The
> pedal morphology of _Confuciusornis_ indicates it was likely a
> ground-dwelling (terrestrial) bird, but one that might have perched
> and possibly sheltered in trees.
> Yes, claw angles indicate ground-foraging by _Confuciusornis_ and by
> the enantiornithean taxa examined by Glen and Bennett (2007).
> However, based on pedal proportions (especially of the hallux),
> enantiornitheans appear to have spent far more time in trees than
> _Confuciusornis_ did. I agree with you that _Confuciusornis_ could
> climb trunks using its large, clawed hands, in lieu of an inability to
> execute a ground-level take-off.
I think calling Confuciusornis terrestrial is taking things too far. The pedal
claw proportions fall within both terrestrial and arboreal ranges, and Chiappe
et al. (1999) note "Relative lengths of the phalanges in the third pedal digit
of Confuciusornis sanctus fall within the transition between birds that spend
most of their time in trees and others that are predominantly terrestrial."
Sure it couldn't perch as well as some enants or passerines, but that hardly
makes it terrestrial. We'd need some study of Aves hallux length equated to
lifestyle as we have for claw curvature to tell. Some modern birds with even
tinier halluces can perch fine, like wood ducks-
http://www.nejohnston.org/Birds/feet/WoodDuck_1.jpg . Confuciusornis really