Mixed roosts in the Montagu’s harrier Circus pygargus during courtship

Mixed communal roosting of Montagu’s harrier Circus pygargus in the pre-laying period was observed on Calcareous Marshes in Eastern Poland from 1992 to 1995. To my knowledge, this behaviour was described in literature for the first time. The communal roosting in Montagu’s harrier during courtship can help in estimation of mate attraction and finally in mate choice. Harriers from communal roosts start egg laying earlier when compared to the outside roosts. Communal roosting as anti-predator behaviour can help with predator detection and provides benefits to all members of the group. The pair formation process has led to disintegration of communal roosting. Males were more common in the roosting places than females. The time of roosting was correlated with the photoperiod. The weather and predators impact delayed the formation of mixed roosting places.