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Hen harrier

size:

43-50 centimeters
wingspan: 100-120 centimeters

color (adults):

males: mainly grey back, blue belly with grey upper chest, white rump, black-winged tips; females: brown back, white ring around upper tail

food:

small rodents (mice, rats, young rabbits and hares) and birds (pheasants, meadow birds and songbirds)

threats:

decline in suitable open landscapes

Dutch status:

nesting bird (96% on Wadden Islands); birds from the north migrate through the Netherlands

habitat

dunes, fields of heather, marshes, fallow fields

reproduction:

3-5 eggs; maturity 2 years

life span:

7 years (maximum known age:+ 17 years)

  • Dut: Blauwe Kiekendief
  • Eng: Hen Harrier
  • Fren: Busard Saint-Martin
  • Ger: Kornweihe
  • Ital: Albanella reale
  • Lat: Circus cyaneus
  • Dan: Bli kærhøg
  • Nor: Myrhauk
  • Frisian: Blauwe Hoanskrobber
Hen harrier, female, foto fitis, adriaan dijksen

Hen harrier

Do you ever see a hen harrier in the Netherlands? Then you are very fortunate! These beautiful birds are having a very difficult time surviving in this country. They are only found in just a few places in this country and their numbers keep dropping. It is unknown why this is happening, but is probably due to a lack of food. Just like the marsh harrier, hen harriers have a shallow V-shaped silhouette as they scan the ground for prey or glide low over the ground. They sleep and nest on the ground.

On Texel


Hen harrier, foto fitis, sytske dijksen

Prior to 1980, hen harriers did not nest on Texel. In those days, Montagu's harriers nested here! Since 1980, hen harriers increased in population on the island, reaching a peak in 1994 with 27 pairs. However the numbers have been declining since then and by 2013, there were only 6 pairs of this rare raptor still nesting here. Probably no young left the nest due to the poor food situation.

  • Nesting harriers

    The hen harrier builds its nest on the ground in a field of heather or a dune slack. That isn't always the safest place. In 2009, two nests were plundered by thieves on Terschelling. Five young disappeared from one nest and three eggs were removed from the other one. There was an obvious path made by people that led to the nests.

    When there is sufficient food around, it is not unusual for males to have multiple females. However, there is often a ranking system among the females. Number one female gets the best treatment and is therefore the most successful.

  • Overwintering

    Hen harriers do not migrate far in the autumn. Many Scandinavian harriers spend the winter between southern Scandinavia and central Europe. The harriers that nest in the Netherlands either spend the winter here or migrate to Belgium, France or England. In early August, the birds depart for their winter quarters, returning to their nesting grounds at the end of March. Studies have shown that hen harriers stay closer to their birth place in the winter than in the past. Even though that means arriving earlier for nesting, it's questionable whether they can find sufficient food, since most of their prey hide from the cold.

  • Population developments in the Wadden Sea region
    Hen harrier, foto fitis, adriaan dijksen

    The first nesting pair of hen harriers in the wadden region was on Ameland in 1940. The first pair nested on Terschelling in 1946, followed by Schiermonnikoog (1954), Vlieland (1970) and Rottum (1991). The population in the wadden region reached a peak between 1990-1994, when 115 pairs were counted. This accounted for 90% of the total Dutch population of hen harriers. In 2012, there were only 11 pairs on the Wadden islands. In fact, none nested on Ameland and they have disappeared from Terschelling and Schiermonnikoog. The hen harrier is on the Red List for threatened bird species.

  • Reasons for decline

    It is unknown why the hen harrier population is declining in the Netherlands. Nesting hen harriers raise enough young; the problems begin particularly when the juvenile birds have to become independent and the adult birds. Researchers who have studied the content of pellets see that the birds have changed their diet. They used to eat lots of pheasants, meadow birds and rabbits. Nowadays they eat lots of smaller prey, such as voles and true mice. Perhaps the raptors are having problems because they must catch more smaller-sized prey. Competition with the marsh harrier, goshawk and buzzard as well as disturbance from people probably also play a role.

    It's also possible that the hen harrier is looking for new nesting and hunting grounds. Hen harrier populations on the German Wadden Islands are growing. Using colored rings, bird experts are trying to discover whether Dutch harriers have moved to Germany. They already know that it happens to some degree.  A female that nested on Baltrum in 2009 had been ringed three years before at birth on Schiermonnikoog.

  • Grazers don't help

    Sheep, goats and cattle are implemented everywhere along the coast to help combat overgrowth in the dunes. Although these grazers help prevent the dunes from filling up with bushes and grass, they have a negative effect on voles. And nowadays, these small mammals are the favorite food for hen harriers. Grazed areas are not only avoided as hunting grounds but also as nesting grounds. Hen harriers themselves can't even hunt in terrain that is totally overgrown, since they can't find their prey. Bird conservators would like to see more variation in the species of grazers and grazing intensity. Fluctuations in time and space could be very positive; customized grazing!

  • Protection
    • Monitoring: Network Ecological Monitoring, Red List
    • Policy: Target Species List, Species Protective Plans
    • National legislation: Flora and Fauna Regulation
    • European Agreement: Bird Directive, CITES ordinance
    • International: Bern Convention, Bonn Convention