Removing American crows and duck nesting success

Abstract

The American crow (Corvus brachyrhynchs) is reputed to be an important predator of duck eggs, but its potential impact has not been evaluated adequately. We removed breeding crows from their territories prior to and during the duck breeding season to test whether duck nesting success would increase. Nesting success in two removal areas did not differ from that of two control areas. Our results are consistent with several studies indicating that removal of one predator species from a community of predators, including corvids, does not lead to predictable increases in breeding success of game birds. Further work is needed to determine the relative importance of different predators and to learn why removal of one predator species is generally ineffective.