Semicolonial nesting and conservation of the Montagu's harrier Circus pygargus in rapeseed fields in Southern Podlasie (eastern Poland)

Agrocoenosis are important nest sites for Montagu's harriers. In 2009, a large semicolony of 14 Montagu's harrier pairs was recorded in a rapeseed field in eastern Poland. The breeding colony arose due to a shortage of crops of suitable height in the period of nest building, caused by unfavourable weather conditions and a delayed onset of vegetation growth. The mean clutch size and hatchling number was 3.62, and the mean number of chicks in pairs that bred successfully was 2.00. Losses in broods due to predation and farming treatments were low (2% and 6%, respectively).