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Old 03-14-2016, 02:33 PM
Broomstick Broomstick is offline
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Location: NW Indiana
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Quote:
Originally Posted by Charlie Wayne View Post
How can you tell that parrots are left-handed? Do you mean that they always stand on one foot and eat by picking up food with the other foot? I'm not sure which foot you would call "dominant".
Not always but according to my (admittedly not exhaustive) research most parrots prefer picking up/holding/manipulating things with one foot over the other. My conures have both definitely favored their left foot for this. The three cockatiels I've had don't seem to pick up/hold/etc. much of anything and if they had a preference I've never been able to figure it out. The lovebirds were less inclined to use their feet as hands than the conures but all three seemed to favor the left when they did such things.

Informal browsing turns this up as a frequent observation, that parrots tend to be left-dominant. It's not as strong as in humans, but it does show up statistically.

Quote:
But that's very interesting. I had a parrot for ten years and I never noticed that she always ate food I gave her by holding it with the same foot.
Not all parrots have a dominant foot, and even those that do tend not to be as preferential as humans.

I should probably point out that avian brains are structured very differently than mammalian brains, and that might well account for some of the differences here. Which is why I speculate that handedness might have have an advantage, but which hand is preferred may be due to random chance in an ancestor. Humans might have had that ancestor as a righty, birds like parrots might have had a lefty in that position.

Most mammals (again, informal research) don't show a preference for one hand over another. The great apes (chimps, gorillas, orangutans) show some tendency towards a dominant hand, but which hand seems a bit random and there are plenty who don't show handedness. Chimps and gorillas might be slightly more inclined to be right handed, and orangutans slightly more likely left handed but the evidence is weak at best from what I've seen.

It might be (note all the qualifications indicating speculation here - it's all over what I've found on the subject) that preferring one hand over the other makes you a better toolmaker/user, in which case the strong tendency to favor one hand makes a lot of sense in humans, but doesn't account for being right handed so frequently as opposed to left. It might account for handedness in parrot species that frequently grasp/manipulate objects, in that specializing with one leg for grasping a perch/supporting the body and the other for finer manipulations also makes sense, for similar reasons as humans, but again which hand is preferred is not accounted for.

Crows also show a preference in such matters - let's get more formal and call it "lateralization" which gets away from "hands" and towards "whatever the critter manipulate with or favors". New Caledonian crows are also tool users and makers and also show a lateralization preference - with most being righties! At least when they're making tools. Here's a bit more on handedness in animals

So... apparently lateralization appears in species that make/use tools and might have something to do with brain organization. Which side is favored seems a bit of a crap shoot, but the more a species makes and uses tools the more likely the majority will favor one side or another.

Bottom line: it appears to be connected to tool making and use, and since humans are so specialized in that role it makes some sense we'd have strong lateralization.