Hen Harrier

Hen Harrier (Circus cyaneus) is a slim long-winged harrier with a white rump; males are mainly grey and white, while females and juveniles are brown. Body shape, bill structure, plumage pattern and voice provide the strongest field characters. Age, sex and season may alter its appearance, so identification should combine several features and careful direct field comparisons with similar species in the same habitat (Wikipedia, general species account).

It hunts by flying low over marshes, grasslands and other open habitats, taking small mammals and birds, and migrates south from colder breeding regions in winter. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds gathering where food is concentrated. Japanese records place it within the country's documented avifauna as a resident, migrant or visitor (Wikipedia, general species account; Wildlife of Japan occurrence records).