Pandionidae is a monotypic family of fish-eating birds of prey.
647–678. The family Alcidae includes auks, murres, and puffins. The young of many bird species do not precisely fit into either the precocial or altricial category, having some aspects of each and thus fall somewhere on an "altricial-precocial spectrum". The spine has cervical, thoracic, lumbar and caudal regions with the number of cervical (neck) vertebrae highly variable and especially flexible, but movement is reduced in the anterior thoracic vertebrae and absent in the later vertebrae. These birds are characterised by a breeding season spent in the temperate or polar regions and a non-breeding season in the tropical regions or opposite hemisphere. Flapping keeps the air current moving to create lift and also moves the bird forward. [4], Primitive bird-like dinosaurs are in the broader group Avialae. Songbirds, parrots and other species are popular as pets. [65] Hole and burrow nesting species tend to lay white or pale eggs, while open nesters lay camouflaged eggs.

Conflicts between an individual fitness and signalling adaptations ensure that sexually selected ornaments such as plumage coloration and courtship behaviour are "honest" traits.

In: K. Padian, ed.

Gauthier and de Queiroz[8] identified four different definitions for the same biological name "Aves", which is a problem. They are found in open country worldwide, mostly in habitats near water.

When the fledglings have their new feathers, they come out of the nest to learn to fly. [185] Birds do not have sweat glands, but they may cool themselves by moving to shade, standing in water, panting, increasing their surface area, fluttering their throat or by using special behaviours like urohidrosis to cool themselves. [257], They may also serve as religious symbols, as when Jonah (Hebrew: יוֹנָה‎, dove) embodied the fright, passivity, mourning, and beauty traditionally associated with doves. Many of the largest flying birds in the fossil record may have been members of the Ciconiiformes. Palaeontologists have found some exceptional places (lagerstätten) where fossils of early birds are found. [4] The largest carnivorous bird was Brontornis, an extinct flightless bird from South America which reached a weight of 350 to 400 kg (770 to 880 lb) and a height of about 2.8 m (9 ft 2 in). It was earlier thought that this high diversity was the result of higher speciation rates in the tropics; however recent studies found higher speciation rates in the high latitudes that were offset by greater extinction rates than in the tropics.
[65] The ribs are flattened and the sternum is keeled for the attachment of flight muscles except in the flightless bird orders. Sleeping birds often use a type of sleep known as vigilant sleep, where periods of rest are interspersed with quick eye-opening "peeks", allowing them to be sensitive to disturbances and enable rapid escape from threats.

Loons are aquatic birds the size of a large duck, to which they are unrelated. Hypercarnivory became increasingly less common while braincases enlarged and forelimbs became longer. [10][29] After the appearance of Maniraptoromorpha, the next 40 million years marked a continuous reduction of body size and the accumulation of neotenic (juvenile-like) characteristics.

Most pet birds are specially bred and are sold in pet shops. Large birds of prey, such as eagles, that spend a lot of time soaring on the wind have wings that are large and broad.

If a flock of birds were flying over a field, they would be calling "Fly! When the bird exhales, the used air flows out of the lungs and the stored fresh air from the posterior air sac is simultaneously forced into the lungs. [65][133] Loons, diving ducks, penguins and auks pursue their prey underwater, using their wings or feet for propulsion,[57] while aerial predators such as sulids, kingfishers and terns plunge dive after their prey.