Ornithology is the study of

Ornithology is the scientific study of birds. It is a branch of zoology that includes the study of their physical characteristics, behavior, and ecology.

Option A is incorrect because mammals are a class of vertebrate animals that have hair or fur and mammary glands that produce milk to feed their young.

Option B is correct because birds are a class of warm-blooded vertebrates that have feathers, wings, and a beak. They lay eggs and are able to fly.

Option C is incorrect because fishes are a class of aquatic vertebrates that have gills, fins, and scales. They lay eggs and are unable to fly.

Option D is incorrect because bats are a type of mammal that are able to fly. They are not birds.