Density, nest site characteristics and breeding rates of the osprey (Pandion haliaetus) in the southern limit of its range in the Western Palearctic (Boa Vista, Cape Verde Islands)

Between 2004 and 2007, we studied density, habitat features and breeding parameters of the osprey (Pandion haliaetus) population in Boa Vista Island (Cape Verde). A total of 79 nest structures were identified, 37 of which were occupied for at least 1 year during the study period. The osprey population ranged between 14 and 18 pairs, and the mean density and distance between neighbouring occupied nests were 2.58 pairs per 100 km2 and 3089 m, respectively. Occupied nests were found to be significantly further from the coastline and roads than unoccupied nests, but the distances from villages were similar. The majority (81.1%) of the 37 occupied nests were easily accessible to humans. Mean clutch size was 2.59, average productivity was 0.76 young/active nest, and breeding success was 58.8% [Correction added on 13 May 2013, after first online publication: the average productivity was changed from 0.72 to 0.76]. Density in Boa Vista was higher than that in other sedentary island populations in the Western Palearctic, whereas the productivity was the lowest of this region. Clutch size did not vary among Western Palearctic populations, but the differences observed in productivity were likely influenced by local factors that in Boa Vista are attributed to nest depredation by the brown‐necked raven (Corvus ruficollis) and to direct human persecution. Résumé Entre 2004 et 2007, nous avons étudié la densité, les caractéristiques de l'habitat et les paramètres de la reproduction de la population de balbuzards pêcheurs (Pandion haliaetus) de l’île de Boa Vista (Cap Vert). Nous avons identifié un total de 79 structures de nids dont 37 furent occupés pendant au moins un an au cours de la durée de l’étude. La population de balbuzards pêcheurs comprenait entre 14 et 18 couples, et la densité moyenne et la distance moyenne entre des nids occupés voisins étaient respectivement de 2,58 couples/100 km² et 3 089 m. Nous avons constaté que les nids occupés étaient significativement plus éloignés de la côte et des routes que les nids inoccupés, mais leur distance par rapport aux villages était comparable. La majorité (81,1%) des 37 nids occupés étaient facilement accessibles pour les hommes. La taille moyenne d'une nichée était de 2,59, la productivité moyenne de 0,76 jeune /nid actif, et le taux de réussite de la reproduction de 58,8% [Rectification apportée le 13 mai 2013, après la première publication en ligne : la productivité moyenne passe de 0,72 à 0,76]. La densité était,