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
Dune shearwater which bred in lava fields. Extinction of the species occurred about 2000–3000 years ago, contemporaneously with the first human settlement of the islands by the Guanches, with the cause likely to be human predation. Dune shearwater The dune shearwater ("Puffinus holeae"), also known as the Canarian shearwater or Hole's shearwater, was a relatively large shearwater which bred in the Canary Islands archipelago of the North Atlantic Ocean. Fossils have also been found in the Figueira Brava cave archaeological site on the western coast of Portugal. The specific epithet honours Mrs Jean Hole who collected fossil material of the species on