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
Calonectris Calonectris Calonectris is a genus of seabirds. The genus name comes from Ancient Greek "kalos", "good" and "nectris", "swimmer". The genus comprises three large shearwaters. There are two other shearwater genera. "Puffinus", which comprises about twenty small to medium-sized shearwaters, and "Procellaria "with another four large species. The latter are usually named as "petrels", although they are thought to be more closely related to the shearwaters than to the other petrels. The taxonomy of this group is the cause of some debate, and it is only recently that the Cape Verde shearwater has been split from Cory's shearwater. The species