Northern Harrier

## Description

The northern harrier (Circus hudsonius ) is a bird of prey. It breeds throughout the northern parts of the northern hemisphere in Canada and the northernmost USA.

The northern harrier migrates to more southerly areas in winter with breeding birds in more northerly areas moving to the southernmost USA, Mexico, and Central America. In milder regions in the southern US, they may be present all year, but the higher ground is largely deserted in winter. This bird inhabits prairies, open areas, and marshes.

The northern harrier was formerly considered to be a subspecies of the Eurasian hen harrier.

## Appearance

The Northern harrier is a bird of prey that breeds in Canada and the northernmost USA. It has the longest wing and tail relative to its body size of any raptor occurring in North America. The sexes of this species differ in their appearance and also in weight with females being heavier. The male's plumage is darker grey than that of the female harrier and the female is also darker and more rufous. The adult male is sometimes nicknamed the "Grey Ghost", because of his striking plumage and spectral aura. The Northern harrier was formerly considered to be a subspecies of the Hen harrier.

## Distribution

Northern harries are found throughout the northern parts of the northern hemisphere in Canada and the northernmost USA. They migrate to more southerly areas in winter with breeding birds in more northerly areas moving to the southernmost USA, Mexico, and Central America. In milder regions in the southern US, they may be present all year. Northern harriers inhabit marshes, moorland, bogs, prairies, farmland coastal prairies, marshes, grasslands, swamps, and other assorted open areas.

## Behavior

Northern harriers are usually seen soaring singly but during winter they may gather in communal roosts to stay warm at night. These birds hunt by day by surprising prey while flying low to the ground in open areas, as they drift low over fields and moors. The harriers circle an area several times listening and looking for prey. They use hearing regularly to find prey, as they have exceptionally good hearing for diurnal raptors, this being the function of their owl-like facial disc. Northern harriers are typically very vocal while they glide over their hunting ground. At other times the female gives a whistled ‘piih-eh’ when receiving food from the male, and her alarm call is ‘chit-it-it-it-it-et-it’. The male calls ‘chek-chek-chek’, with a more bouncing ‘chuk-uk-uk-uk’ during his display flight.

## Diet

Northern harriers are carnivores that hunt primarily small mammals. They prefer voles, cotton rats, and ground squirrels. Up to 95% of the diet comprises small mammals, however, they also regularly hunt birds such as sparrows, larks, pipits, small shorebirds, and the young of waterfowl and galliforms. They may sometimes supplement their diet with amphibians (especially frogs), reptiles, insects, and even bats if these are available.

## Reproduction

Northern harriers are polygynous; they don’t form pairs and one male mates with several females. During the breeding season, each male will maintain a territory averaging 2.6 km2 (1.0 sq mi). These birds nest on the ground or on a mound of dirt or vegetation. Nests are made of sticks and are lined inside with grass and leaves. Four to eight (exceptionally 2 to 10) whitish eggs are laid. The eggs are incubated mostly by the female for 31 to 32 days. When incubating eggs, the female sits on the nest while the male hunts and brings food to her. The male will also help feed chicks after they hatch, but does not usually watch them for a greater period of time than around 5 minutes. The male usually passes off food to the female, which she then feeds to the young, although later the female will capture food and simply drop it into the nest for her nestlings to eat. The chicks fledge at around 36 days old and reach reproductive maturity at 2 years in females and 3 years in males.

## Population

### Population threats

There are no major threats facing this species at present.

### Population number

The IUCN Red List and other sources don’t provide the number of the Northern harrier total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.