Montagu’s Harrier

Distribution

This species can still be found throughout most of the Western Palearctic. In most European countries there is at least a small population, except in Norway where it is not present. The breeding range extends as far east as the Urals, whereas the most western population is that of Portugal. Breeding also occurs in northern Africa, mostly in Morocco. In Great Britain, the species is limited to southern England. In Ireland the species is rarely seen, and mainly in the South, although there are a number of breeding records, the most recent from 1971.

Habitat

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, 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, for breeding the Montagu's harrier requires a large open area, 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.

Reproduction

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 300–400 m 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.

Food

The diet consists mainly of small rodents, small birds, bird eggs, reptiles and large insects.

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 ), 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. In a manner typical of harriers, prey is passed between partners in the air: The female flies underneath the male, who drops the prey for her to catch. The male hunts over a large area up to 12 km away from the nest. The female hunts closer to the nest, up to 1 km away, and only after the young have hatched.

Migration

The Montagu's harrier is a long distance migrant. Birds from Eurasia spend the winter in sub-Saharan Africa, while those from the eastern part of the range migrate to the Indian subcontinent. In Europe, the first birds start to move at the beginning of August and most have left by mid-October. They travel over a broad front, crossing the Mediterranean at various points, and only a small number are observed at migration choke points. Western birds don't go further south than the gulf of Guinea, but some eastern birds travel as far as South Africa. In Africa, their diet is composed mostly of insects and birds, and it is possible that they follow locust swarms.

Spring return peaks in April, and most birds have arrived by May though there is evidence that first-year juveniles spend their first summer in the winter quarters