SPEED OF MIGRATION AND MIGRATORY FLIGHT LENGTHS OF PASSERINE BIRDS RINGED DURING AUTUMN MIGRATION IN SWEDEN

The autumn migration speed of 62 passerine species was estimated on the basis of short-time Swedish ringing recoveries (n = 2212). The average migration speed was lowest among short-distance migrants (mean = 28 km d-1) and highest among long-distance migrants (mean = 60 km d-1). The maximum individual speed exceeded 100 km d-1 in several species. For many species the migration speed increased along the route and tate migrants also seemed to attain a higher speed than early conspecifics. In some cases adult birds migrated significantly faster than juveniles. Recoveries made 1-3 days after ringing were used for estimating the length of migratory flights. The average flight length among nocturnal migrants (177 km) was significantly longer than that of diurnal migrants (111 km). Most flights made by nocturnal migrants lasted for less than half the dark period. Such relatively short flights made during the first part of migration may relate to the slow initial migration speed found in many species.