Birds of a (leg) feather

I’ve commented on the Musings before about the presence of feathers on the legs of Archaeopteryx an important aspect of their anatomy that had gone largely overlooked (or at least unremaked upon) for far too long and of course is more interesting in the light of fossils like the ‘four-winged’ Microraptor. While the idea that flight might have evolved from a four-winged stage (via elongate leg feathers to provide the extra wings) is interesting, one wonders why before Microraptor it had garnered so little attention. I’m referring really to birds like this vulture:
The elongate feathers on the leg are really pretty obvious here and indeed to anyone who ahs ever watched them fly, or other big birds of prey like eagles and buzzards the same thing is clear (especially when striking or coming in to land) – some birds have very Archaeopteryx like feathers on their legs. The question I would pose is just why were feathered legs on Archaeopteryx such a surprise, or for that matter those of Microraptor or Anchiornis? Anyone looking at a decent range of birds would see a clade that had very similar feathers clearly using them in an aerodynamically useful way (if largely to steer or break rather than to generate lift). It’s not hard to see that maybe an early bird or proto-bird still struggling to generate sufficient lift or power (or for that matter steering) might have benefited from an additional source of control and breaking. People have blindspots and before anyone asks, no I have not dug through the last 150 years of flight research to check how often four winged dinosaurs / leg feathers / control during the origin of flight were mentioned or expounded upon, but I would argue that: a) most people were surprised by the appearance of Microraptor / Archaeopteryx legs feathers (including a large number of specialists) and b) they really should not have been given that plenty of birds have and use them. As echoed recently in the SV-POW posts on necks, why do palaeontologists insist on working only on fossils when we have living animals to compare them to?

Note: I know the feathers themselves are quite different between living and extinct taxa are different and may not have been used in even vaguely similar ways, my point is that we can see birds do things with leg feathers now, so why was the possibility of leg feathers in the early evolution of birds ignored?

3 Responses to “Birds of a (leg) feather”

  1. 1 Zach Miller 16/07/2009 at 5:50 am

    Indeed, I wonder the same thing, Leg feathers are very obvious on the eagles up here, Golden and Bald. Ravens have feathers on their legs that, in addition to having an aerodynamic function, are also used in threat and courtship displays.

    I’m surprised that nobody (as far as I’m aware) has looked into the aerodynamic function of these feathers in living birds, and then apply that to fossil taxa.

  2. 2 Silver 13/02/2014 at 3:45 am

    I don’t know how much this actually is any more than anecdotal; but I’ve kept chickens and there are several genes that can cause feathered vs. scaly legs.

    One drawback to feathered legs especially with a ground bird like a chicken is that they get tend to get more skin and feather parasites than scaly legged birds. Untreated the parasites (typically lice and mites) can cause serious damage and even be fatal on a young bird. Which is likely this trait is not found in wild birds

    • 3 David Hone 13/02/2014 at 8:44 am

      That is most interesting, thanks! The ranges of odd traits that pop up under domestication or selective breeding are extremely useful form this point of view to help reveal what may be possible, and especially when coupled with information about how it affects them. Cheers for this.

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