Rather small, compact hawk; about the size of Red-shouldered Hawk, smaller than Red-tailed Hawk. Adults are solid brown above, barred reddish-brown below with bold black-and-white tail bands. Immatures similar, but with blotchier markings below and thin, diffuse tail bands. Distinctive shape in flight: note the short tail, straight leading edge of wing, and bulging secondaries in flight. Listen for high-pitched, piercing whistle coming from woodlands during breeding season. Known for forming massive flocks called kettles during migration, when it travels from the U.S. and Canada all the way to winter in Central and South America.