Western jackdaw amounts of silicaceous and calcareous grit to aid digestion of vegetable food and supply dietary calcium. Opportunistic and highly adaptable, the western jackdaw varies its diet markedly depending on available food sources. They have been recorded taking eggs and nestlings from the nests of the skylark ("Alauda arvensis"), Manx shearwater ("Puffinus puffinus"), razorbill ("Alca torda"), common murre ("Uria aalge"), grey heron ("Ardea cinerea"), rock pigeon ("Columba livia"), and Eurasian collared dove ("Streptopelia decaocto"). A field study of a large city dump on the outskirts of León in northwestern Spain showed that western jackdaws forage there in the early morning and
Shearwater Shearwater Shearwaters are medium-sized long-winged seabirds. There are more than 30 species of shearwaters, a few larger ones in the genus "Calonectris" and many smaller species in the genus "Puffinus". The "Procellaria" petrels and "Bulweria" were believed to belong to this group, but are only distantly related based on more recent studies, while the "Pseudobulweria" and "Lugensa" "petrels" are more closely related. The genus "Puffinus" can be divided into a group of small species close to "Calonectris" and a few larger ones more distantly related to both. These birds are most common in temperate and cold waters. They are pelagic