Breeding strategied of Ravens Corvus corax in an Oceanic Island Ecosystem (El Hierro, Canary Islands)

Abstract

The breeding population of Ravens on El Hierro consists of between 99 and 120 pairs. Most territories were found at altitudes of 600 metres a. s. l. or lower. Altitude had an important effect on the early stages of clutches, specially in the lower zones or in those at heights less than 900 metres a. s. l. There were no great differences in the timing of nesting in comparisan with continental areas. Clutch size and breeding sucess were lower than in practically all continental zones, which suggests a relationship to the limited resource capacity of island ecosystems.