Thinking about the bird migration in the Strait of Gibraltar, images of raptors like Black Kites, Honey Buzzars, Booted and Short-toed Eagle accompanied by the always elegant White Storks and Black Storks, among many other species of birds, come to your mind. However, during end of October and early November, other groups of birds face the crossing of the Strait in very high numbers such as the small finches (Goldfinches, Greenfinches, Serins, and Linnets), other passerines, and the larger ones, the Griffon Vultures. The latter forming concentrations of many hundreds on the north shore waiting for the good wind of the northwest and a good visibility of the african coast that ensures a crossing to the African continent.
However, if we think about migration in a different way, different from that NORTH-SOUTH movement and we look at the sea, we will find one of the most impressive spectacles that occur in Strait of Gibraltar waters, the migration of the Scopoli's Shearwater.
The mediterranean subspecies of this shearwater (Calonectris diomedea diomedea) breeds mainly on islands and islets of the Mediterranean Sea. During the month of October, its autumn migration begins and they leaves the Mediterranean to carry out one of the most impressive journeys made by a living creature. Each year these shearwaters cover trips that exceed 70,000 kilometers crossing the Atlantic Ocean in both hemispheres following the highways that provide the conditions of favorable winds. On these trips, they will cross the Strait of Gibraltar (Cádiz) and during the last days of October and early November, you can see concentrations of this species that astound you.
The unique conditions of the Strait of Gibraltar make it possible to observe this phenomenon from coast, since the shearwaters are close enough to be able to observe them easily. During the weeks of 'migration peak' you can get to see more than 7,000 shearwaters/hour ... in a migratory passage where you cannot see different flocks, but as if it were a large snake, constant flows of Scopoli's Shearwaters moving slowly with its characteristic glide in a westerly direction. The total population of this species is estimated at just over 450,000 shearwaters, and from the Island of Tarifa (Cádiz) you can see many of these numbers in a few days of observation.