Egg Shell Dumps and Crow Corvus cornix Predation on Simulated Birds' Nests

Abstract

The use of egg shell dumps by hooded crows is described and its energetic value was discussed. The distribution of depredated simulated nests and the distances that marked eggs were transported to shell dumps were used to study the crows'' foraging pattern. It is favorable if the whole egg content can be transported to the nestlings simultaneously. The empty shells should not be left close to the crows'' nest where predators could be attracted. The adult crow should be able to see its nest and potential predators from the site where it opened the eggs. Only a fraction of all eggs taken by crows are transported to shell dumps. If this fraction is determined the number of shells found can be used to estimate the total egg predation in the area. Of the depredated eggs, 17% were recovered on shell dumps. The territorial crows seem to use exclusive feeding territories that are less intensively used far from their nests.