The Corvidae family contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs and nutcrackers. They are considered the most intelligent of the birds. They are medium to large in size, with strong feet and bills, and a single moult each year (most passerines moult twice). Most species have bristle-like feathers covering their nostrils. They are omnivores having a varied diet. Corvids are found worldwide except for the tip of South America and the polar ice caps. [abstracted from Wikipedia]