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Tripedal Birds; You heard me!
Topic Started: Feb 1 2012, 11:10 PM (4,757 Views)
Spugpow
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Here's the original proposal:

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Since forelimb mobility is apparently such a problem, what would a bird do if it became a heavy grazer like a cow? Hadrosaurs and other ornithopods without the same anatomical restrictions as birds always became quadrupedal to support their expanded guts, but that's never been an option for avian grazers like moas and ostriches.

That leaves only the beak as an accessory support structure. Most birds don't do much with their beaks besides eat and preen, but parrots actually use theirs extensively when climbing. Potentially, a parrot that adopted the grazing lifestyle could continue the use of its beak as a third limb on the ground.

In fact, the Kakapo is a real grazing parrot. And yes, it does use its beak for locomotion both in the trees and on the ground, as you can see in some of these videos: http://www.arkive.org/kakapo/strigops-habroptila/ . The Kakapo, while large for a parrot, is still a fairly small animal. If it attained the size of a cow* (or moa), is it that much of a stretch to imagine it using its beak to help support its weight? Think of a kangaroo using its tail as a fifth limb when walking slowly; likewise, the giant kakapo would trundle along on its feet and beak when grazing, only raising up on its hind limbs to run.


*This is all supposing, by the way, that the Kakapo isn't on the edge of extinction.


Anatomy said:
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Would they be able to maintain a 'gallop', so to speak, or rather bursts of quick movement with that kind of set up of appendages? (In terms of them outrunning predators, generally surviving.) Or, to run, would they just sprint about on two legs, beak held aloft? The mental images are intriguing.


Good question. I think, like hadrosaurs and kangaroos, the parrots would run on two legs (swaying ponderously, booming with alarm etc. :D ). The very largest ones, however, (could birds get larger than mammals because of their pneumaticity?) might require a tripod of support at all times. They probably wouldn't run so much as shuffle in a hurry; in my minds eye I see it as a kind of asymmetrical loping movement.

Speculative Flish said:
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The only problem I see is unless their beak was REALLY long, their heads would be constantly close to the ground and likely hidden by grass, so it would basically be blind unless running or standing. (if they stood upright)


BTW, kakapos are arboreal (yet flightless) frugivores, I think you mean the closely related Night Parrot which really does graze.


Good point about keeping the head down. On the one hand, grazing and locomotion would more or less verge into one another: every "step" of the head would yield a mouthful of grass. On the other, keeping a lookout for predators would be challenging. This might impel the parrots to become social, like other grazers (and other parrots).

It also stands to reason that their eyes would be high up on their heads, like a hippo's.


Edited by Spugpow, Feb 1 2012, 11:38 PM.
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Nocturnal Sea
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To address the visibility problem-- they could also be restricted to shortgrass praires, where their heads are long enough to see over the grass while the head is down. A social structure would also be ideal-- maybe several sentry birds could take turns standing guard on elevated ground, such as praire dog mounds (or whatever the local equivalent would be).
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colddigger
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Big long tough beaks with tongues. Big and tough to support the creature and long to allow them less distance to move their head to look for predators.
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JohnFaa
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The birds could have extremely long beaks in order to both use them to support themselves and to still keep an eye on predators.

To feed, they'd rely exclusively on the tongue to grab food.
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Spugpow
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Interestig ideas. I suppose the beak could be somewhat hoof-shaped as well.

I'll have to make a picture.
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Zoroaster
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Spugpow
Feb 2 2012, 10:13 AM
Interestig ideas. I suppose the beak could be somewhat hoof-shaped as well.

I'll have to make a picture.
I don't think you have any choice Spug... do it - you know you want to!
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Cephylus
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This is a very intriguing idea, it calls forth some interesting ideas and possibilities into my mind, and I think it may actually be possible; at least more plausible than the idea of modern birds evolving their forearms into a support structure and going quadrupedal (I am not an expert on this, but I have read once -possibly by Johnfaa- that birds lack the muscle groups for their wings to become a supportive structure?) and also a lot more original and a lot more interesting.
The idea of birds reaching prehistoric hardrosaurian weights or at least weights similar to elephants and rhinos while still retaining a bipedal stance is kind of hard to vision. They would probably be wobbling about and topple over at the slightest disturbance. Maybe by evolving incredibly large feet and robust legs, but they would still be kind of unbalanced :)
The tripedal stance would require a very bizarre way of movement, though. Perhaps they would move in a sort of galloping way, putting their beaks forward with their legs following after, kind of pole vaulting on their beaks.
And they would also have to change the basic shape of the beaks. Besides having to be incredibly long, they would also need to end in an extremely flattened, expansive surface. With their current common shape, the beaks would just pierce the ground surface and get stuck. Not to mention having to completely change their skull structure, they would basically have to re-locate their eye sockets to the back of their heads to see properly or at the center of their foreheads.
The fact that the beaks aren't flexible, not having joints and thus not being able to bend, will also prove a disadvantage in locomotion. Plus, since the beaks will be completely useless outside of their supportive function, won't they also have trouble catching and eating food? These tripedal birds will have to keep their beaks closed the whole time they are walking, which is kind of disadvantageous when it comes to eating.
On the other hand, an arboreal bird which uses its beak as a supportive structure to grasp onto branches as well as a manipulative organ seems less far fetched and easier to envision. Far better than the traditional feathered-hoatzin-gibbon thing as an arboreal bird people usually come up with.
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Nanotyranus
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What about a bird that walks with its mouth open, or a bird that walks with a beak extension? That would solve the eye problem. Also, long prehensile toungues.

A long, single-jointed thing might be easier to move. I dunno. Maybe it could walk in a foot-beak other foot-beak gait, and gallop in a pole-vault way.
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Anatomy
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Jointed leg that can "lock" to form a beak?
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T.Neo
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Hold on just a darn second. What's the problem with large bipedal birds? There were some strikingly large bipedal theropods in the Mesozoic. Why can't birds be bipedal and still large?
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colddigger
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They're evolving these ones from a bird that already uses its beak to move around...
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Fleeshster
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And would be digesting huge amounts of Cellulose.

@Spugpow's answer: I guess those would solve the problems if it just appeared from no where, but the parrot would have problems while it was still adapting to this movement, since the beak can't instantaneously become long in one mutation, same goes with the eyes.
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T.Neo
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Quote:
 
They're evolving these ones from a bird that already uses its beak to move around...


Not my point. I think this concept is very interesting, but I mean, we've got all this quadrupedal bird stuff, now this... has anyone actually realised that you can have pretty heavy bipeds during this whole saga?
Edited by T.Neo, Feb 2 2012, 03:51 PM.
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Nanotyranus
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I have. Remember my towerbirds and quill-bone tail birds?
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T.Neo
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Quote:
 
I have. Remember my towerbirds and quill-bone tail birds?


No, I don't. I don't pay as much attention to future/alternate evolution as I should.
Edited by T.Neo, Feb 2 2012, 07:16 PM.
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