Autumn migration of Montagu’s Harrier Circus pygargus and Marsh Harrier C. aeruginosus at the southern tip of Öland

Abstract

We have analysed the autumn passage of Montagu’s Harrier Circus pygargus and Marsh Harrier C. aeruginosus at Ottenby (56°12'N, 16°24'E), Sweden, based on data collected by Ottenby Bird Observatory during 1972—1998. The observations were made by the ringing team and, hence, possibly less accurate than data from more detailed raptor counts previously carried out at Ottenby and Falsterbo (55°23'N, 12°50'E), Sweden. However, we found a coherent picture when comparing the time of passage found in this study with that of previous studies. For instance, the median date of Montagu’s Harrier (22 August) is identical to what was found in a detailed three-year study at Ottenby in 1977—1977. It is, however, a few days earlier than the median date further south at Falsterbo. The Marsh Harrier passage peaks in late August, similar to the situation at Falsterbo. The main difference between this study and the standardised counts at Falsterbo is the relatively low proportion of birds identified to age and/or sex. Hence, we could not reveal any statistical difference in seasonal timing between age and sex groups.