Birds are vertebrates with feathers, modified for flight and for active metabolism. Birds are a monophyletic lineage, evolved once from a common ancestor, and all birds are related through that common origin. There are a few kinds of birds that don't fly, but their ancestors did, and these birds have secondarily lost the ability to fly. Modern birds have traits related to hot metabolism, and to flight:
- horny beak, no teeth
- large muscular stomach
- feathers
- large yolked, hard-shelled eggs. The parent bird provides extensive care of the young until it is grown, or gets some other bird to look after the young.
- strong skeleton
There are about 30 orders of birds, about 180 families, and about 2,000 genera with 10,000 species. Most of them don't live in Michigan, though there are about 400 species that do.
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