Some hover above a body of water and dive in, others wade and jab, and still others swim at or under the surface of the water. Some species specialize in stealing the prey of other species. Many falcons, hawks, and owls specialize in capturing avian or mammalian prey, and thus have excellent eyesight and are powerful and silent flyers. Lots of bird species live in flocks, at least part of the time. Many species flock during the winter, but are territorial during the breeding season.
Bird flocks are often competitive rather than cooperative assemblages.
The benefits of flocking include increased vigilance for predators and greater foraging efficiency. Costs include increased transmission of parasites and increased competition for resources. Migration is a well-known component of bird behavior, but the evolutionary advantage of migration is poorly understood. A number of hypotheses have been proposed, but none is well-supported for all bird species. The feats of migration of some bird species are legendary.