Welcome to the Natural History Museum's Bird Site. The Bird Site has been designed to provide general information about bird

• evolution & diversity
• anatomy & physiology
• adaptations & behavior
• flight mechanics
• conservation

The material is appropriate for educators and students of all ages. If you would like to comment on this material, please email us at educate@nhm.org.

Birds belong to the Class Aves in the Kingdom Animalia. Birds are the only animals that have feathers and all birds have feathers. Other characteristics of modern birds include: forelimbs modified into wings, no teeth, scales on the feet, a four chambered heart, egg-laying, clavicles (collar bones) united as furculum (or wishbone) and warm-bloodedness.

Scientists have divided the Class Aves into around 25 to 30 orders. Each order is subdivided into families of related genera and species (kinds). Scientists group birds together by searching for common structural characteristics of their anatomy and similarities in the genetic material.

Because of their ability to fly, birds inhabit nearly every part of the Earth - from the oceans and frozen polar zones to steaming rain forests and barren deserts. Their wide-ranging abilities and occupation of diverse habitats have allowed them to diversify into over 9,000 species. By comparison, there are only 3,000 species of amphibians, 6,000 reptiles, and 4,600 mammals. The insects, with over 800,000 species, form the most dominant class in the world.

Birds are incredibly diverse in size, color, and lifestyles. They range in size from the 2.5 inch, 0.08 ounce Bee Hummingbird to the Wandering Albatross with an 11 foot wingspan. Arctic Terns fly 15,000 miles each year as they migrate from the Arctic to the Antarctic and back! Sooty Terns are thought to be able to fly continuously for several years without touching down. Other birds such as ostriches, rheas, emus, kiwis, and some parrots and rails, are flightless and depend on running, camouflage, or isolation for protection from predators. Penguins confine their flying to under water. In comparison to mammals, which range from 100 ton whales that swim in the ocean, bats that fly through the air, horses that run, monkeys that climb, and 0.08 ounce shrews that tunnel through the ground, birds are much less diverse. The ability to fly has imposed strict constraints on their overall body plan.