The quick-wittedness and great adaptability of many of the typical black crows (genus
Corves) may partly account for their wide distribution over four continents. At any event, intelligence accounts for the versatility in feeding behavior that has allowed them to survive in such harsh environments as deserts, tundra, and cities.
Experimental studies with ravens have suggested that under some controlled conditions they can “count” up to five or six. This species and the jackdaw performed better than parrots, pigeons, and chickens in simple experiments designed to test intelligence.
Wild crows appear to use their intelligence to good effect in obtaining food. For example, Carrion crows learned to drop freshwater mussels from the air onto land surfaces to break them open and obtain the soft body of the animal within. Accompanying Herring gulls would repeatedly drop the mussel onto soft mud, but the crows were much quicker in
Learning to select hard surfaces.
Another example was reported by a gamekeeper who had been checking on the location of pheasant nests with clutches of eggs. On returning to several of the pheasant nests he found they had all been robbed by crows along several hundred meters of hedgebanks. Later observations showed that carrion crow had learned to watch the gamekeeper to obtain information on the location of the nests.
Other instances have been reported of ravens, Carrion crows, and jackdaws being quick to rob nests of gulls or birds of prey during brief periods when they were left unattended owing to the presence of birdwatchers in the vicinity. Indeed, nests of some of the scarcer birds of prey such as eagles are less likely to be deserted as a result of human disturbance than they are to be robbed by crows while the parent birds have been frightened away from the nest.