Long-term memory in egg predators: an experiment with a hooded crow

Consistence in risk of nest predation between consecutive nesting attempts at the same site may be explained by at least two hypotheses: (1) Nest sites differ in detectability; (2) predators memorize the location of previously detected and depredated nests. We tested these hypotheses using an individually marked male Hooded Crow preying on artificial ground nests. We used ten pairs of nests; one of the nests (experimental) was placed in exactly the same spot as one of the nests preyed upon by this crow in the previous year, while the other (control) was placed 30-40 m away. The crow preyed upon the experimental nests first in spite of the two kinds of nest having the same degree of vegetative cover. This supports the memory hypothesis and suggests that in birds that suffer egg predation by corvids there will be selection for site shifts after nest predation.