Swallows

About 90 species, nearly cosmopolitan. Aerial insectivores with long pointed wings, tiny bills and a very wide gape, taking all their food in flight. Many are colonial, and several build their nests from mud pellets carried one at a time, by the thousand. Their dependence on flying insects leaves them exposed to cold snaps, when insects stop flying altogether, and steep declines in several species are attributed to falling insect abundance.