RE: Microraptor also ate fish

[Jason Brougham <jaseb@amnh.org>]

I've wondered about the evolutionary origin of bird's ability to float on 
water. It turns out that water repellency of feathers is dependent on the 
spacing and radii of the barbs. I wonder if any Yixian fossil feathers are 
preserved in fine enough detail to get these measurements? I guess we'd only 
really suspect a true aquatic habit if we saw webbed toes.

Wettability and phylogenetic development of feather structure in water birds. 
A.M. Rijke. J. Exp. Biology (1970) 52, 469-479. 

It turns out that all feathers, even in pigeons, are pretty highly water 
repellent and, paradoxically, some of the lowest water shedding values are in 
aquatic birds like cormorants, which take on water in the outer feathers (but 
tightly retain air trapped in the inner feathers) to reduce buoyancy and allow 
diving.  We all know a wide range of birds drop into the water and then take 
off from the surface with prey, including kingfishers, a huge array of 
seabirds, and even ospreys. I've seen films of fruit bats Pteropus taking off 
from water surfaces. there are also many films on Youtube of Bald Eagles that 
have seized large fish in the water, and then are too heavy to get aloft. At 
that point they swim ashore with their wings. I read that this is known in many 
raptors. 

https://www.youtube.com/watch?v=dISfWRtjTFU

One paper actually finds that iridescent plumage is poorly water repellent, so 
we might expect that Microraptor would show especially poor performance in 
water, having been found in one study to be iridescent.

Eliason, C.M. and M.D. SHAWKEY. 2011. Decreased hydrophobicity of iridescent 
feathers: a potential cost to shiny plumage. Journal of Experimental Biology 
214:2157-63. 

________________________________________
From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Mickey 
Mortimer [mickey_mortimer111@msn.com]
Sent: Sunday, April 21, 2013 8:44 PM
To: dinosaur@usc.edu
Subject: RE: Microraptor also ate fish

Tim Williams wrote-

> > Equally possible but also equally likely to be due to scavenging in both 
> > cases,
>
> I tend to think that hunting a diverse array of prey was well within
> the abilities of _Microraptor_. Yes, it is possible that _Microraptor_
> scavenged. But _Microraptor_ was certainly adapted for a predatory
> lifestyle. So when a small fish/bird/mammal ends up in its stomach,
> I'm going to give _Microraptor_ some credit and assume that it could
> hunt its own prey. And "prey" includes fish and arboreal birds, as
> well as small mammals.

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.

> > Then he points out Sinocalliopteryx also ate birds and was near certainly 
> > not arboreal. All of
> > this would seem to nullify much of the impact of the paper.
>
> I disagree. The situations (_Sinocalliopteryx_ vs bird /
> _Microraptor_ vs bird) are not quite the same - because the birds in
> each case are very different. The bird eaten by _Sinocalliopteryx_
> was a _Confuciusornis_, which has a morphology consistent with it
> being terrestrial (although the morphology also suggests it spent some
> time in trees, and possibly even perched).
>
> On the other hand, the bird eaten by _Microraptor_ was an
> enantiornithean, and Jehol enantiornitheans tend to be arboreal. So
> given the respective lifestyles of the birds, one could argue (and I
> am) that the _Confucusornis_ was more likely to be caught on the
> ground than in the trees. Conversely, the enantiornithean was more
> likely to be caught in trees than on the ground.

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).  And while confuciusornithids may not have been 
able to take off from the ground, they could prob
 better than enants given their large hands and manual unguals I and III.  But 
moreover, arboreal birds at le
g as
enantiornithines spend lots of time on the ground today (certainly
enough to commonly get caught on the ground by cats), so I don't think
enants being a bit more arboreal than confuciusornithids influences the
liklihood of being caught on the ground much.

> > I hate to use the term misleading, but the abstract states "Several 
> > morphological adaptations of
> > Microraptor are identified as consistent with a partially piscivorous diet, 
> > including dentition with
> > reduced serrations and forward projecting teeth on the anterior of the 
> > dentary." Is this really
> > right to say when the paper identifies only these two characters as 
> > indicating piscivory? "Two
> > (which does not mean several) adaptations are identified, including these 
> > two"?
>
> Well, two is better than none at all - even if those two characters
> have a wide distribution among maniraptorans. I get what you're
> saying here Mickey: Are we reading too much into the available
> evidence? Nevertheless, we do have a small predatory theropod with a
> fish inside it. Is it such a leap of faith to posit that the theropod
> caught the prey alive, and (therefore) that it was a versatile and
> opportunistic hunter? I think this is a reasonable hypothesis.

Well, what I'm saying there is that two does not equal several, and saying 
something is supported by several lines of evidence including x and y generally 
indicates that more than x and y support it.

But yes, reading too much into the evidence is my main point here.  Since when 
are papers written based on leaps of faith?  It's a reasonable hypothesis, but 
it's equally reasonable the fish was scavenged.

> _Microraptor_ seems to have scansorial abilities, although I dispute
> that it was arboreal (i.e., spent most of its time in trees). But
> _Microraptor_ didn't need to have arboreal adaptations in order to
> hunt prey in trees. Similarly, _Microrapto
> adaptations in order to hunt prey in the water.
>
> Again, I'm prepared to accept the hypothesis on offer: That
> _Microraptor_ was an opportunistic and 
> prey on the ground, in the trees, and in shallow water. I hold this
> hypothesis as more likely than the alternative: That _Microraptor_ was
> limited to terrestrial prey, and any arboreal or aquatic animals it
> ate were the result of scavenging. This seems unnecessarily
> constraining.

But who ever proposed the latter hypothesis?  No one, certainly not me.  Maybe 
it caught the fish, maybe it scavenged it.  Maybe it caught the bird in a tree, 
maybe on the ground.  Maybe it scavenged it.  We just don't know.  All we know 
is that Microraptor ate birds and fish, and since that doesn't support any 
unexpected behavior, I frankly don't see why it deserves to be the topic of a 
paper.  Did anyone ever doubt Microraptor would eat a bird or fish if it found 
them dead, or would be capable of catching them if it found them alive?

Mickey Mortimer