Reproduction of the Osprey (Pandion haliaetus) in the island of Menorca (western Mediterranean, Spain)

Authors: TRIAY, R.

Published: Volume 42(1), June 1995. Pages 21-28.

Language: Spanish

Original Title: Reproducción del Aguila Pescadora (Pandion haliaetus) en la isla de Menorca (MediterrÁneo occidental)

Keywords: clutch size, laying phenology, Menorca, Osprey, Pandion haliaetus, population density and productivity.


This study presents information collected between 1980 and 1994 concerning the breeding biology of the Osprey (Pandion haliaetus) in Menorca (Balearic Islands, Spain). Nineteen different nest sites are known, 11 of which are no longer occupied. The population during the 1950's was estimated to have been between 11 and 13 nesting pairs. Building new nests or rebuilding old abandoned ones has only been observed in pairs in their first or second breeding year. The present density of occupied nests is one for each 7.5 km of coastline, and one pair for each 1.1 km in the area of highest concentration. In 1990 an apparent recovery began following a period of eighth years of stability (1982-89). The average annual growth of the nesting population from 1980 to 1994 has been 8.8%. From two pairs in 1980 the number has increased to six pairs in 1994. The mean laying date was April 2; 51.6% of clutches were laid between 20 and 31 March. The earliest date was March 12, and the latest May 9. The first and second year pairs tended to lay later. The average size of the clutch was 2.88 eggs, this being normal for the subspecies haliaetus. The average productivity during these 15 years was 1.33 (fledged young/pair with clutch), oscillating between 0.33 and 2.25. The Menorca population has recovered with an average productivity of 1,00 young/pair with clutch between 1980 and 1987. There is no evidence of interchange of individuals between the Northern European and Mediterranean populations.

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