Cramp & Simmons (1980) stated for the Hen Harrier Circus cyaneus that the vocalisations are 'confined largely to the breeding season', but with 'quick chattering-type calls heard occasionally, however, at or near communal night-roost in winter; usually uttered by one or more birds when disturbed or mobbing human or other mammalian intruders.' Neither C r a m p & Simmons (1980) nor Wa
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