Two hens, but a single nest: an unusual case of polygyny by Hen Harriers in Orkney

In June 1981,I was told of a nest of Hen Harrier Circus cyaneus on the East Mainland of Orkney with ten eggs, and two females in attendance. Since an unusually high percentage of first-year males (25%) bred on the West Mainland of Orkney in 1981, and one was even bigamous (recorded only once previously in 1971, Balfour & Cadbury 1979), my immediate reaction was that one of the two brown h

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