Variation in the abundance of Blackcaps(Sylvia atricapilla)wintering in an Olive(Olea europaea)orchard in southern Spain

The abundance of Olive crop production and scrubland fruits in the Mediterranean Basin, which vary according to climate, strongly affect frugivorous species such as Blackcap. When the crop is poor in Olive plantations in southern Spain, because of unfavourable weather during the ripening period, a large proportion remains on the trees because the harvest is not profitable. There is also a considerable decrease in wild fruit in scrubland in such years. Thus in the 1981–82 winter, Olive orchards in Pilas had a much superior fruit resource than adjacent scrublands and, correspondingly, a higher Blackcap density. In the following winter fewer olives were available and the abundance of Blackcaps decreased in the Olive plantation and increased in scrublands. These results suggest an irruptive and opportunist behaviour of Blackcaps similar to that of other frugivorous and granivorous species.