Interinsular variations in the spring and summer diet of the Raven Corvus corax in the Canary Islands

Abstract

This paper presents the first data on the diet of the Raven Corvus corax in the Canary Islands, based on analysis of 2315 pellets collected from all of the islands and islets in the archipelago. The Ravens on three groups of island showed differences in diet, but in all cases the diet was clearly omnivorous, both in its qualitative and quantitative composition. It is evident that a broadening of the Raven's trophic niche has ocurred in comparison with those living in continental areas, While the diet has a strong plant component on the wetter islands (frecuency of occurrence >87%), an appreciable animal component in the diet (principally vertebrates) is more frequent on the drier islands of the archipelago (frecuency of occurrence >96%). The composition of the plant component of the diet varied markedly from one island to another. Remanins of refuse are more commonly found in the Raven's diet on the central and western islands. We concluded that while the animal diet is essential from the bioenergetic point of view, the vegetation diet is only a complementary food source. The Raven plays an important role in seed dispersal among the different habitats within cach island.