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Re: Science feather strength debate

> Moreover, we would both agree that 20% doesn't matter to extant migratory 
> birds with highly derived flight apparatus, but modern birds have a lot of 
> spare capacity. They can stoop at 200 mph, hover in mid air, and fly 
> thousands of miles! In an animal that is barely capable of aerodynamic 
> locomotion, 
> like any hypothetical ancestor of birds, 20% could be a crucial difference 
> between ascending flight and gliding.>

One point worth mentioning here is that while some modern birds do indeed 
execute high-load maneuvers, those that do also have stronger limbs than those 
that do not.  Peregrine falcons, for example, have humeri over 6 times stronger 
than those of an albatross, relative to body mass (i.e. they can take 6+ times 
as many body weights of force).  Therefore, one of the key methodological 
points in comparing the structural strengths of feathers or bones in living 
birds to fossil ones is to use relevant living taxa - don't use hummingbirds 
and falcons as comparisons for Archaeopteryx, for example.  Doing so will 
inevitably make Archaeopteryx look underbuilt.  By contrast, something like a 
grebe, which is still quite a derived and reasonable flyer, does not have limbs 
all that much stronger than the most basal birds, relative to mass (I am using 
the Yalden mass for Archie in that comparison).


--Mike H.