What ARE birds?

So, so far birds are extant-land dwelling animals that have not necessarily interacted with humans.

Are animals smaller than rollypollies birds?
Are flightless birds birds?
Are any of these cottontail rabbits birds?
Are gorillas birds?
Are lemurs birds?
Are bonobos birds?

Some.
Some
Out of that list, only the Eastern cottontail and the tapeti are birds.
Gorillas are not birds.
Lemurs are not birds.
Bonobos are not birds.

Monarch butterflies are birds.
Ladybugs are birds.
Some skunks are birds... I think.

Burds are not a reference to something.

Let me know if you need a clearer hint. I may be able to drop a hint that should narrow down your questions.