avian

Avian is an adjective relating to birds and, in a taxonomic sense, to the class Aves. The term derives from Latin avis, meaning bird. Birds are endothermic, egg-laying vertebrates distinguished by feathers, beaked jaws, and a high metabolic rate. Most have wings and are capable of flight, though many lineages are flightless. The skeleton tends to be light, with hollow bones and an efficient respiratory system that includes air sacs.

Bird reproduction is by laying hard-shelled eggs, with parental care ranging from minimal to extensive. Many species form long-term pair bonds and exhibit diverse nesting strategies. The group Aves comprises numerous orders and families; modern birds trace their ancestry to theropod dinosaurs within Archosauria, with major diversification in the Cenozoic.

Ecologically, birds occupy nearly every habitat. They perform roles as pollinators, seed dispersers, predators, and scavengers, and are often important indicators of environmental health. Many species migrate seasonally, using celestial cues and, in some cases, geomagnetic information.

Humans interact with birds in numerous ways. Domesticated species such as chickens, turkeys, ducks, and geese are important for food; other birds are kept as pets or studied in science. Birds face threats from habitat loss, pollution, invasive species, and climate change, leading to conservation concerns for many species worldwide.