What ARE birds?

Non-blue whale whales are not birds.

Extant reptiles besides turtles, lizards, and alligators are not birds.

Some non-dragon flying fictional creatures are birds.
Half-human fictional creatures are not birds.

Carnivorous plants are not birds.
Grain crops are not birds.
Tubers are not birds.

Frogs are not birds.
Salamanders are not birds.
Newts are not birds.
Amphibians apart from the above are not birds.

Some primates that are not gorillas or monkeys are birds, maybe.

Dung beetles that are not scarabs are not birds!

Birds are not creatures that are referenced in a specific forum adventure or grand battle.
Birds are creatures that are referenced in a specific video games!