Translations:Adventist Youth Honors Answer Book/Nature/Birds/5/en
From Pathfinder Wiki
Each of these things seems quite unique, but as we look at the other classes of vertebrata, we find that birds are not the only creatures that can fly. There are flying fish, gliding snakes, gliding frogs and bats. Each class of vertebrates has the capability of crude flight, and bats at least can match the flight ability of the birds. We must also note that not all birds are capable of flight (penguins, ostriches and others are incapable of flight).
