Eurasian Marsh-Harrier

Circus aeruginosus

The western marsh harrier is a large harrier, a bird of prey from temperate and subtropical western Eurasia and adjacent Africa. It is also known as the Eurasian marsh harrier. Formerly, a number of relatives were included in C. aeruginosus, which was then known as "marsh harrier". The related taxa are now generally considered to be separate species: the eastern marsh harrier, the Papuan harrier of eastern Asia and the Wallacea, the swamp harrier of Australasia and the Madagascar marsh harrier of the western Indian Ocean islands. Source

Where it is now

In the last 8 weeks this bird was recorded 6,077 times across 34 areas (each area is a 5 degree square).

See the Eurasian Marsh-Harrier on the live map

Movement and weather

Each season it is first heard regularly where daytime highs are around 9°C (typically 6 to 11°C, from 12 areas). That holds across 25° of latitude, which suggests its timing follows temperature more than the calendar.

Over the weeks it was present in the past year, its centre in Europe ranged from 42°N in March to 66°N in June, about 2,700 km apart.

Arrival dates

The week it was first heard regularly in each region, after at least six weeks away. Dates differ from south to north, so a region has a range.

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Figures are effort corrected and come from automatic sound identification, which makes mistakes. How this is measured and how it compares with human observers.