Copulatory behavior of semi-colonial Montagu's Harriers

The copulatory behavior of the monogamous Montagu's Harrier (Circus pygargus) was studied between 1992 and 1995 near Madrid, Spain. Copulations started around 20 days before laying, and typically stopped at the end of the laying period, Copulation frequency peaked just before the start of the laying period, averaging 2.2 copulations day(-1). Females copulated on average 39 times per brood Copulation rates apparently were not related to food provisioning by males except in the early pre-laying period. At least 5 and up to 11 (4-8%) of the copulations observed were extra-pair copulations (EPCs), and all occurred within the fertile period. Montagu's Harriers increased their copulation rate in situations of increased EPC risk: solitary pairs copulated for a shorter period of time and at an overall lower frequency, whereas pairs nesting in clumps showed higher copulation rates with increasing number of neighboring pairs. This increase was most marked during the laying period, when there is a higher risk of EPCs producing extra-pair fertilizations.