Why are there no animals with three legs?

If "Why?" is the first question in science, "Why not?" must be a close second. Sometimes it's worth thinking about why something does not exist.

Feather mites may help clean birds' plumage, study shows

Feather mites help to remove bacteria and fungi from the feathers of birds, according to a new study by University of Alberta biologists. In fact, the relationship between these mites and their hosts could be considered mutualism, ...

Mate choices of barn swallows tied to diverging appearances

If you are a male barn swallow in the United States or the Mediterranean with dark red breast feathers, you're apt to wow potential mates. But if you have long outer tail feathers in the United States, or short ones in the ...

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