Satellite tracking of Cory's shearwater migration

Transmitters were attached to four adult male Gory's Shearwaters (Calonectr is diomedea) caught at their breeding sites off Crete, Greece, in autumn 19 98. The birds had left the Mediterranean by the beginning of December. Two were last recorded in the eastern tropical Atlantic in January/February. Th e other two wintered east of the Mid-Atlantic Ridge, one at about 10 degree s N, the other one in equatorial waters, and could be tracked until return migration in March/April. The seasonal variation in travel speed is in acco rdance with a conventional pattern of migration with phases of migration an d wintering, rather than continuous movement throughout the nonbreeding cyc le. The birds left the Mediterranean later and wintered farther north than expected. We suggest that the known longitudinal dine in body size, morphol ogy, and vocalizations of Gory's Shearwater may also be found in migration behavior.