There are many subtle differences, but generally, birds lay their young in eggs and mammals give live birth.
Nothing. Birds are not mammals.
Mammal.
They connect to air sacks in the body and bones. This makes them more efficient that mammal lungs.
No. Nighthawks are birds and birds are not mammals.
No. Nighthawks are birds and birds are not mammals.
A penguin is a bird. Many scientists say that makes it a dinosaur as well as birds can be classified as the only surviving branch of the dinosaurs.
No, they are birds
Birds
The Emperor penguin is not a mammal, it is like all other birds and penguins.
None of the above ! They are birds !
Penguins are birds.
Penguins are birds.