Aves (Birds)

Birds are warm-blooded vertebrates characterized by feathers, toothless beaked jaws, laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds occur globally ranging from tiny hummingbirds to huge flightless ostriches.

There are about ten thousand species of birds and categorized into passerines and non-passerrines. More than half of all bird species are passerines (perching” birds). Birds have wings which enable their flight, and these vary depending on their flight types and lifestyles. The only known groups without wings are the extinct moa and elephant birds.

Wings are modified forelimbs, giving birds the ability to fly. In some groups such as the ratites, penguins and some endemic island species, the wings have been modified for swimming or reduced due to the of the need for flight as a mean to evade predators.  

Many social species of birds pass on “cultural” knowledge across generations. Birds are social, communicating with visual signals (courtship displays), calls and songs, and participating in cooperative breeding and hunting, flocking, and mobbing of predators.

Most bird species are socially monogamous, usually for one breeding season at a time, sometimes for years, and rarely for life. Other have polygamous breeding systems that with one male to many females or, rarely, polyandrous with one female with many males. Birds reproduce by laying eggs which are internally fertilised through sexual reproduction. The eggs are laid in a nest and incubated by the parents, followed by an extended period of parental care after hatching which included feeding nestling chicks sometimes even for a few days after leaving the nest and fledging.

Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs, meat, and feathers. Songbirds, parrots, and other species have also been exploited for the pet trade, while Guano (bird excrement) is harvested as fertiliser. Today, human activity threatens about 1,200 bird species with extinction, though conservation efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry in many parts of the world.

Source: Wikipedia

Bird Families