What ARE birds?

Are hermit crabs birds?
Are roly-poly/pill bugs birds?
Are lobsters birds?

Some other felidae are birds.
Some other canidae are birds.
Canadian geese are birds.
Some otters are birds.
Some weasels are birds.

Some hermit crabs are birds.
Roly-polies are birds.
Lobsters are not birds.

Are slugs birds?
Are rabbits birds?

Are caterpillars birds?
Are moths birds?
Are butterflies birds?

Some slugs are birds.
Some rabbits are birds.
Some caterpillars are birds.
Some moths are birds.
Some butterflies are birds.

Are sea slugs birds?
Are cone snails birds?
Are koalas birds?

Sea slugs are not birds.
Cone snails are not birds.
Koalas are not birds.

I think this is around the time I give a hint by answering my own question?

The European starling is a bird.

Are birds animals that are known as "the common" version of their animal type?

Such as Lutra lutra, the common otter?

Birds are not animals that are known as "the common" version of their animal type.

Aw dang I thought I had it, with the spectacled caiman aka the common caiman and the European starling aka the common starling being birds.

Well, while we're at it, is the European otter a bird?

The European otter is a bird.

Is the African Starling a bird?

Are Indian elephants birds?
African elephants?

Siberian tiger?

Canadian geese?

I couldn't find the African starling, so it's not a bird.

The Indian elephant is not a bird.
The African elephant is not a bird.
The Siberian tiger is not a bird.

As previously mentioned, the Canadian goose is a bird.

bumping

Are axolotls birds?

Axolotls are not birds.

I couldn't find the African starling, so it's not a bird.

you need to look harder

you need to look

in africa

Are birds welcome in the Space Consortium?

Birds are not things which are welcome in the Space Consortium.

Birds:

• spectacled caiman
  
• domesticated cats
  
• domesticated dogs
  
• Canadian geese
  
• Roly Polies
  
• European Starling
  
• European otter
  

Some are birds: Crocodiles, birds, snails, invertebrates, turtles, raptors (birds), crabs, geese, canidae besides domestic dogs, felidae besides domestic cats, otters, weasels, hermit crabs, slugs, rabbits, caterpillars, moths, butterflies,

Are animals that cannot survive on land birds?
Are animals that only breathe with gills birds?
Are extinct animals birds?

Are dwarf crocodiles birds?
Are any of the extant species of crocodiles birds? (listed in the spoiler)

SpoilerShow

American crocodile?
Slender-snouted crocodile?
Orinoco crocodile?
Freshwater crocodile?
Philippine crocodile?
Morelet's crocodile?
Nile crocodile?
New Guinea crocodile?
Mugger crocodile?
Saltwater crocodile?
Cuban crocodile?
Siamese crocodile?
West African crocodile?
Crocodylus raninus?

Are birds immortal cosmic space entities?

Animals that cannot survive on land are not birds.
Animals that only breathe with gills are not birds.
Extinct species are not birds.

These are not the conditions I am looking for, however.

American crocodiles are birds.
Saltwater crocodiles are birds.
It can be debatable whether New Guinea crocodiles are birds, but I will say no, they are not.

Every other crocodile species are not birds.

Birds are not immortal space entities.