What ARE birds?

So we know that....

Birds:
Centipedes, Alligators, Bald Eagles, Penguins, Chickens, Spiders, Crows, Peacocks, Owls, Tyrannosauruses

Not Birds:
Humans, Snakes, Bees, Rotifers, Cockroaches, Worms, Mice, Annelids, Shrimp, Crocodiles, Gharials, Caimans, Ants, Canaries, Cassowaries, Housecats, Vultures, Herons, Ducks, Doves, Sparrows, Dodos, Tabby cats, Emus, Kiwis, Seagulls

Some are birds:
Birds, Reptiles, Domesticated Animals, Flightless Birds, Primates, Marsupials, Passerines

Are strict-herbivores birds?
Are insects birds?
Are sperm whales birds?
Are blue whales birds?
Are zoofights birds?
Are platypuses birds?
Are tasmainian devils birds?
Are velociraptors, ala jurassic park birds?
Are Squid birds?