In regards to the definition of what a "bird" is, I'm just going to throw this out here. There were some rumblings not too long ago (a few years) about the idea of incorporating all of the birds into the reptile group, or folding the crocodilians and birds together into an archosaur group. Either way "Aves" would effectively cease to be its own MAJOR taxonomic group (more like "Squamata" within the group "Reptilia"). The ornithology professors flipped shits when they first heard of that though.
I personally support making a separate archosaur group since birds and crocodiles really aren't all that different: no less different than a whale, a bat and [maybe] a platypus yet they're classified together. IMO the current definition of a "bird' that separates them from other reptiles is extremely tenuous: Beaks, feathers, warm-blooded, and can fly. Turtles have beaks, Bats can fly, Great White Sharks are warm blooded, and feathers are really just fluffy scales.
What was that about being off topic? Oops. As for the OP: Birds almost certainly evolved from a type of small dinosaur; if not then at the very least they shared a very close common ancestor.
Edited by Tupinambis, : No reason given.
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