Why do birds have feathers instead of fur?

Feathers are uniquely bird structures made of keratin, the same protein found in human hair and nails. They evolved for multiple functions: helping birds fly, trapping heat for insulation, shedding water, and creating visual signals for mates or rivals. Unlike fur, feathers can form precise aerodynamic surfaces on wings and tails, allowing efficient lift and steering. Fossil evidence shows feather-like structures appeared before modern birds, and some non-bird dinosaurs also had feathers. Today, feathers are one reason birds can live in everything from Arctic tundra to tropical forests.