Nocturnal spring migration on Mallorca - schedules of departure and passage

Authors: LIECHTI, F., STEURI, T., LÓPEZ-JURADO, C., RIBAS, P. L. D., REIS, M. A. and BRUDERER, B.

Published: Volume 44(2), December 1997. Pages 207-213.

Language: English

Keywords: flight directions, infrared observations, Mallorca, migratory intensity, nocturnal migration, sea-crossing, spring and take-off phase.

Summary:

A passive infrared device was used at the northern coast of Mallorca to study the departure of nocturnal migrants from the island during three weeks in April 1995. As the main take-off phase of the birds was within an interval of 0.5 to 2h after sunset and the south-to-north extension of the island is about 50 km, the frequency of birds declined rapidly about 3h after sunset, when the last birds from the south of the island passed the northern coast. During three nights the observations were extended beyond midnight to see the passage of migrants from the Spanish mainland and from Africa. The first birds having crossed the Mediterranean Sea from Africa flew across the observation site about 6h after dusk, indicating a high (wind-supported) average flight speed of 17 ms-1 (60 km/h). In two nights the passage continued until 11h after sunset, i.e. until dawn. These all-night observations, in combination with a few moon watch data recorded simultaneously to the norrth and south of the island, suggest that, under fair weather conditions, the number of birds landing on the island before the end of the night may be relatively small. Based on the distinct starting period and the diurnal course of migration, reasonable estimates of the distance to previous resting areas seem possible. This is an important result for a project investigating migration simultaneously by various methods (radar, infrared, moon watching) at Mallorca and the southern coast of Spain, and by moon watching along the Mediterranean coast from Italy to Portugal.

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