Montagu's Harrier

This species can be found in a middle-latitude band of predominantly temperate climates, but also in Mediterranean, and boreal zones. Although it has been found nesting up to 1,500 m (4,900 ft), it is essentially a lowland species, and nests mostly in broad river valleys, plains, and levels bordering lakes and the sea. It can breed in wetlands, though these are often smaller and drier than those used by the marsh harrier. It also utilizes heaths, dunes, moors, and can be found in the steppe. It adapts to shrublands in gorse or heather and to areas planted with young conifers. When no other suitable habitat is available this harrier will nest in agricultural farmlands where it is vulnerable to early harvesting. Amongst these it chooses especially grasslands and cereal crops such as wheat, barley, oats and colza. In western Europe, up to 70% of the population breeds in artificial habitats.

In short, Montagu's harrier requires a large open area for breeding, with sufficiently tall ground vegetation to afford cover without being overgrown. It favours posts on which both male and female can rest and survey the breeding area: these can be fenceposts, small trees, or rocky outcrops. When hunting, in any season, it prefers areas of low or sparse vegetation where prey is more visible. Densely settled areas are generally avoided and it is highly susceptible to disturbance.

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 (33 ft) apart. Semi-colonial nesting is not due to a shortage of nesting sites, but arises rather from the need to provide a better defense against predators. The actual area defended by both partners covers only 300–400 m (980–1,310 ft) 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. …

The diet consists mainly of small rodents, small birds, bird eggs, reptiles (including snakes) and large insects (mainly Orthoptera, which are numerically the most common). As this bird has a wide distribution, it will take whatever prey is available in the area where it nests; in the northern range it will mainly take ground squirrels and rabbits, whereas in southern Europe, it mostly takes small reptiles and large insects. In areas where the food supply is composed almost exclusively of rodents, the breeding success depends greatly on the cyclic fluctuations of vole populations. At times they regurgitate. Prey is caught while flying along fixed routes at low heights and constant low speeds (c. 30 km/h (19 mph)), as is typical of harriers. The flight is considered lighter and more dexterous than other harriers enabling it to take more agile prey. When possible it often follows the edges of various vegetation to catch its prey by surprise. This is taken after a short stoop, though fast running animals and flying birds can be chased over a short distance. During the breeding season, the male will provision the female and later the young with food. The rate of provisioning increases from 5 to 6 times per day during incubation to 7 to 10 times per day when young have hatched, though the male can be handicapped by wet, foggy or windy weather. …