Adult: dark gray coloration on back, white underneath with fine dark bars across white belly. Blackish head and black sideburns, with yellow eye-ring. Yellow small, sharply hooked beak. Long pointed wings, with black and white checkering all across underbelly and underwings.
Juveniles: More buff colored underparts, densely streaked in dark brown. Brown mask, instead of black, no yellow eye-ring or yellow around beak. Pale eyebrow and whisker pattern.
One of the most widely distributed warm-blooded terrestrial vertebrates.
Breeding: found almost all over the world; absent as a breeder only from the Amazon Basin, the Sahara Desert, central and eastern Asia, and Antarctica. In North America, breed in parts of central US, but mainly in northern Canada, Alaska, and Greenland.
Non-breeding: in coastal California and most of Mexico, the populations are seen year-round, while in inland California, the population is only there during non-breeding months. Seen throughout the gulf coast in non-breeding months.
Migrating: Migrate throughout all of inland United States and Canada and southwestern Alaska.
Nearly any open habitat during migration, with preference for barrier islands, mudflats, coastlines, lake edges, and mountain chains.
Nest at elevations of up to 12,000 feet, as well as along rivers, coastlines, and in cities.
May mate for life.
Territorial and courtship displays include high circling flights by male, spectacular dives and chases by both sexes.
Male feeds female during nesting.
Nest on cliff ledge, hollow of tree, on tall buildings or bridges, or sometimes in old nests of other birds. Do not build nest, but lay eggs in simple scrape.
Female lays 2-5 eggs of 2 inch length, and incubates them for 29-32 days.
The hatchlings are helpless, covered in white down, with eyes closed.
Eat many hundreds of species of birds, swooping down on them mid-flight.