Duże grupy noclegowe błotniaków łąkowych Circus pygargus we wschodniej Polsce

So far, the communal roosting of the Montagu’s Harrier Circus pygargus is poorly known. The largest breeding populations of this species known from Poland occur in the Mazovian Lowland and in the Biebrza Basin. Also the largest roosting assemblages of the the Montagu’s Harrier were recorded there in mixed groups with the Marsh Harrier Circus aeruginosus. It is likely that such large assemblages of birds reduce predation risk, and are so called „information centres”for young individuals.