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Re: Science feather strength debate



On Nov 12, 2010, at 12:10 PM, Jason Brougham wrote:

> 
> On Nov 12, 2010, at 11:44 AM, Don Ohmes wrote:
> 
>> On 11/12/2010 11:24 AM, Jason Brougham wrote:
>>> Only kiwis and other terrestrial ratites, probably.
>> 
>> Are you sure kiwis can't? Have their joints "reverted" to the constrained 
>> condition? That would be very big news, imo, and even outside the realm of 
>> pure speculation. Mind if I poll the list for info on that?
> 
> No, I'm not sure. It's just a  guess. I'll look into it.
> 
>> 
>>> But, as I say, Meinzer spent months doing fieldwork with them, and he 
>>> reported that Roadrunners don't flap as they leap into the trees, and he 
>>> has three or so photographs showing them vaulting upwards with tightly 
>>> folded wings.
>> 
>> 8' vertical in a single bound, zero flap? Er, cue polite skepticism...
>> Granted, the scamps have some groovy little legs. But that is a lot of 
>> body-lengths, and wings are good/necessary to stabilize when on a perch in 
>> any case.
> 
> I know, that's what amazed me, too. I can't guarantee that they really leap 
> up a full 8 feet, but Mienzer's photos seem to place the above his head.
>> 
>> Anyhow, if they aint flapping, where is the relevance to wing evolution? 
>> "Ground-forage, tree-sleep" is definitely a viable lifestyle.
> 
> The ancestral form, which had rudimentary wings for brooding the nest, and 
> which could fold them tightly to prevent impediments to running (as per Hopp 
> and Orsen, in Feathered Dragons, 2004) could have leapt up into trees to 
> roost and/or forage when they were not breeding. Then these nesting wings 
> could have become exapted, and undergone selection for parachuting down from 
> the roosts (it would just save time and calories if they could jump down from 
> tree crowns rather than climb down, allowing them to forage in trees with 
> less expenditure of energy).  From there, further strengthening, lengthening, 
> and streamlining of the wings and feathers could eventually allow gliding, 
> then flapping, and this lineage may have increased the proportion of time 
> they spent foraging in trees proportionately.
> 
> This may have some support from the fact that Archaeopteryx's toe phalangeal 
> proportions show that it corresponds to birds which forage both on the ground 
> and in trees. When I did some back of the envelope calculations using 
> Hopson's phalangeal method (New Perspectives on the Origin and Evolution of 
> Birds) I found that Microraptor's proportions were terrestrial, but near the 
> overlap with arboreal birds. I also found that Anchiornis came out close to 
> vultures, which feed primarily on the ground, but also roost.
>> 
>> Cycads (thinking Sago Palm here) are highly climbable (and perch-able) 
>> BTW... like I had a dog that could do that once, when motivated w/ a frisbee.
> 
> No kidding? That is pretty cool.
> 
> Jason Brougham
> Senior Principal Preparator
> American Museum of Natural History
> jaseb@amnh.org
> (212) 496 3544
> 
> 

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544