Set a thief to catch a thief: brown-necked raven (Corvus ruficollis) cooperatively kleptoparasitize Egyptian vulture {Neophron percnopterus)

摘要

Our study describes how brown-necked ravens (Corvus ruficollis) are able to take advantage of an ordinarily inaccessible, high-quality food source by relying upon their innovative and manipulative thinking capabilities to exploit methods used by Egyptian vulture {Neophron percnopterus) to overcome the problem. In five observed interactions, the ravens were first seen in the vicinity of an abandoned clutch of ostrich eggs {Struthio camelus). The area was frequented by a pair of Egyptian vultures that bred on the cliffs across the road from the nature reserve. The Egyptian vulture exhibits tool use in birds, and is able to crack the hard shells of ostrich eggs by lifting a rock in the beak and pounding at the egg till it breaks open or cracks. If the egg is only cracked, the vulture inserts its narrow bill into the fissure and widens it by opening the mandibles. Pieces of eggshell are removed from around the crack in order to further open the egg. This is the point at which the pair of ravens attacked the vulture and harassed it till it abandoned the egg and left the area. The ravens then jointly enjoyed the contents of the egg which was otherwise inaccessible to them because of the strong egg shell.