The vertebrate class Aves includes the birds, an extremely distinctive and successful clade, with an estimated 9000 species worldwide, including the snowy owl pictured here. Although descended from the dinosaurs, birds have evolved remarkable specializations for flight: a unique "one-way" breathing system, light yet strong hollow bones, a skeleton in which many bones are fused or lost, powerful flight muscles, and -- most importantly -- feathers.
You can navigate deeper into the birds by selecting "Systematics"!
UCMP Special Exhibit: Vertebrate FlightVisit our series of pages on the wonder of flight in vertebrates, including a discussion of avian flight.
Interested in birds? There are several good ornithology sites on the Web. Check out the California State University BioWeb listing of ornithological sites, or the list of Electronic Resources on Ornithology. All of these have extensive lists of links to Web sites. Birding on the Web is also an excellent site.
We also maintain our own list of On-line Ornithology Collections and Resources.
For a remarkable set of images of birds in flight, check out How Birds Fly. Serious avian aficionados will be interested in the great multivolume reference book, The Birds of North America.