Birds live and breed almost everywhere, including parts of Antarctica. The largest populations of birds occur in warmer, tropical climates. Most birds are active during daylight hours but some bird species, such as owls, are active at night or during twilight.
Bird bones are very lightweight which enables them to fly with feathers that facilitate flight. Feathers, or plumage, provide camoflage to hide from predators, but also colorful displays for birds to be able to recognize each other. The formation of feathers on the birds vary within species depending upon the age, social status, and sex. Male birds are generally more colorful than females. Feathers also provide insulation to help keep the bird warm in the winter and cool in the summer. Birds have very good color vision but not so good with the sense of smell.