Western Marsh Harrier

Western Marsh Harrier (Circus aeruginosus) is a large long-winged harrier; males combine brown, grey and black, while females are mainly dark brown with a creamy crown. 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 quarters reedbeds and marshes in low buoyant flight, taking birds, eggs and small mammals, and northern populations migrate south from western Eurasian breeding areas. 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).