Montagu's Harrier - Social Behaviour and Breeding

Social Behaviour and Breeding

It can be both solitary and gregarious at times, both during the breeding season and in winter quarters. A breeding pair may associate with others to form loose colonies, with as many as 30 nests in the same area, sometimes as close as 10 m apart. Semi-colonial nesting is not due to a shortage of nesting sites, but arises rather from the need to provide a better defence against predators. The actual area defended by both partners covers only 300-400m around the nest, and in case of colonial nesting the response to predators may be communal. Other species attacked and mobbed include large raptors, corvids, and foxes.

Reproduction begins with the return of both partners to the nesting site, at which point both male and female will start displaying. The display consists of various sky-dances and aerobatic figures that vary according to each individual. Both sexes will display, crying loudly, though the males' displays are more frequent and spectacular.

Montagu's harriers breed for the first time when two or three years old, but occasionally one year old females may attempt to nest. Pairs form on the territory, when returning from migration. As the birds are tied to their former nesting sites, they probably mate with the same partner every year. The nest is built by the female, always in tall vegetation. It is a simple construction made of grass, used only for one season. The female lays 3 to 5 eggs which are incubated for 27–40 days. The young leave the nest after 28–42 days and are independent two weeks later.

The males may be polygamous, then having to feed two females and later two broods, either simultaneously or consecutively.