BIRD

Birds are a group of warm-blooded, egg-laying vertebrates constituting the class Aves. They are characterized by feathers, a beak without teeth, and a high metabolic rate supported by a complex respiratory system. Most birds can fly, though some lineages are flightless. Birds are found worldwide in nearly every habitat, from arctic tundra to tropical forests and urban areas. They range from the tiny bee hummingbird to the flightless ostrich and include diverse groups such as songbirds, waterbirds, and raptors.

Anatomy and physiology are adapted for flight and energy efficiency. Feathers provide insulation and enable flight; wings and a lightweight skeleton with hollow bones reduce weight. Birds have a beak adapted to their diet, a four-chambered heart, and a highly efficient respiratory system that uses air sacs. Most birds see well and have acute hearing. They lay eggs with hard shells, incubate them, and care for the young until fledging.

Behavior and ecology vary widely. Diets include seeds, fruits, nectar, insects, fish, and carrion. Many birds migrate seasonally, while others are resident. They use vocalizations and visual signals for communication, defend territories, and form social groups. Nesting behaviors range from simple ground scrapes to complex woven structures.

Reproduction and development: Birds reproduce sexually and lay eggs after mating. Eggs are usually incubated for a period determined by species. Offspring hatch as altricial (helpless) or precocial (relatively mobile) and require varying degrees of parental care.

Conservation and human interactions: Birds face threats such as habitat loss, climate change, pollution, hunting, and invasive species. Conservation measures include protecting habitats, legal protections, monitoring populations, and reducing hazards in urban areas. Birds are valued for ecological roles such as insect control and seed dispersal, and for cultural and recreational importance through birdwatching.