They are not THAT closely related; bats are mammals, not birds. Both mammals and birds are vertebrate animals.
There is none beyond that all animals are related and that bats and birds are both land-dwelling vertebrates. Birds, bats, and insects developed flight independently of one another.
Bats and birds are not closely related. Bats belong to the order Chiroptera, while birds belong to the class Aves. They are both capable of flight, but their wings are structurally different - bat wings are made of skin stretched over elongated finger bones, while bird wings are made of feathers.
Bats and bears . . . they're both mammals. A bird isn't.
Bats do, birds do not
Birds and bats
no bears are not birds so their not related to birds
Bats are not birds as they have no feathers, talons, beaks, or any organ specifically related to birds. The bat's wings are also not the same style as bird's wings. Bats seem to have the same structure in their wings as the human hand. And, they do not lay eggs, they give live birth.
Both bats and birds are warm-blooded vertebrates.
Bats are mammals, birds are not. Birds lay eggs, bats do not.
Bats have fur but birds do not. Bats are mammals that give birth to live young, whereas birds give birth by way of the laying of eggs.
Bats are not birds. Bats are flying mammals. Some birds have a rudimentary echolocation capacity. These birds are the oilbirds of South America, and the cave swiftlets of Asia.