Most diurnal birds of prey are monogamous. Some birds keep the same mate for several years, such as ospreys, while others have different mates each year, such as snail kites. In some groups of Harris' hawks, monogamous breeding pairs are assisted by a number of nonbreeding helpers, mostly previous offspring. A few species are polygynous or polyandrous. Polygyny is when a male mates with more than one female at a time.
Many harriers are polygynous.
For migratory species, breeding territories are usually reestablished before pairs are formed. Aerial displays may also be used simultaneously, or sequentially, to attract new mates, and for bonding between established pairs. Pair displays may include high speed dives, chases, mutual talon grabbing and cartwheeling, and food passing. Other pair bonding behaviors include mutual roosting, cooperative hunting, courtship fights, mutual preening, nibbling, courtship feeding, nest inspections or nest building, and copulation. Copulation occurs when there is cloaca to cloaca contact.