Delayed nest predation: a possible tactic toward nests of open-nesting birds

Abstract

Predators use various tactics to find and depredate bird nests. This study examines a possible tactic of visually orientated predators termed “delayed nest-visit”. This consists in remembering the positions of incubating parents and subsequent easy depredation of eggs when the parents are away from their nests. Conditions for use of this tactic were experimentally simulated by installing artificial nests with quail eggs and plastic dummies of northern lapwings (Vanellus vanellus) at 11 actual breeding grounds with various habitat conditions in southern and eastern Bohemia, Czech Republic. Habitat, presence of the dummy, and their interaction significantly affected nest survival. While 17.2 % of the nests baited with the dummy were depredated, this occurred in only 6.9 % of the nests without the dummy. This depredation rate was affected by the visibility of the dummies in particular habitats. The results suggest that predators may remember the nest position to delay their first visit to a previously located bird nest from a remote place and may use this tactic to easily capture the clutches. The use of this tactic showed that at least some predator species are able to apply much more sophisticated approaches in search of birds' nests than previously assumed.