Why are hen harriers so interesting?
Appearance - The male is grey above, white below, and with black wing tips. The female is much larger, cryptic brown and streaked-off white below. She has a white ring marking at the base of her tail (the scientific name for harriers, Circus, may come from the Greek word for a ring, kirkos, referring to the female’s ringtail). Most other birds of prey species have less marked differences in appearance and size between the sexes.
Hen harriers in Spring and Summer
Courtship display – The male performs a spectacular looping skydancing display to entice a female to mate with him. This involves the male circling over the breeding grounds before plummeting earthwards, only to sweep upwards at the last moment, roll over on his back at the top of the climb before diving downwards again. Repeated dozens of times, this can last for up to quarter of an hour at a time. Skydancing generally occurs between late March and early May. Displaying seen late in the season may well indicate a failed nest and should be reported as quickly as possible.
Harems – Some males pair with up with several females, and have to work phenomenally hard to provision each of them whilst incubating their eggs, and then helping feed the chicks.
Food passes – The male often feeds the female by flying close to the nest and then summoning her to leave the nest, fly toward him, and then back flip to catch the prey dropped from above. These food passes may occur only twice or thrice a day, and close to the nest.
Roosts – As darkness falls in autumn, some harriers roost communally in reed beds, marshes or on heaths. With up to a dozen birds milling over the roost site as darkness sets in, this is one of our finest but increasingly rare wildlife spectacles.
Migratory movements - Most hen harriers leave the moor in early autumn, moving south to lowland farmland and coastal marshes. Some of Scotland’s birds, mainly males, migrate to France and Spain in the winter – we are using satellite tracking to reveal these movements.
Conservation – Scotland has the bulk of the British population. Unfortunately, there is a long history of persecution of hen harriers, especially on grouse moors where they take young grouse, in addition to other prey. By the end of the 19th Century hen harriers were found only in Orkney and the Hebrides, where they were not persecuted. The return of the birds to the mainland was slow, with the population reaching a peak in the 1960s and 70s.
Nesting facts – Hen harriers lay 4-6 eggs during late April–May. Incubation lasts 30 days, and their young fledge in 28-32 days, beyond which they depend on their parents for a further month.
Hen harriers in Winter
Hen harriers are found over a wide range of open habitats in winter. They can often be seen drifting low over rough grassland, inland and coastal marshes, farmland and moorland, searching for small mammals and birds. They can also occur around open forestry plantations. Most move away from upland moors during the winter but some do winter here if the weather is mild. Some birds move long distances with satellite tagged Scottish birds being seen in France and Spain.
Harriers are a little smaller than buzzards but can appear quite large due to their long broad wings and long tails. Adult males are white below with pale grey upperparts and distinctive black wing tips. Younger males often have more mottled/dirtier looking grey upperparts. Females are mottled brown with a brown tail with darker bars. Juveniles are similar to females in appearance, though sometimes more buff-coloured on their underparts. All ages and sexes show a white rump patch which is most striking on females or juveniles as it stands out more clearly against the brown plumage. Females can be noticeably larger than males.
They are most often seen on their own, but they do roost communally in the winter, so you can see a few birds associating with each other at certain times. If you see birds together in mid-late afternoon they may be gathering to roost and it is important that you report the location as roosts are sensitive to disturbance and have been subject to persecution.
(Updated November 2015 - new request for winter sightings of hen harriers)