Switches in covering of eggs in grey partridge Perdix perdix clutches during laying and incubation

Abstract. Covering of eggs is important antipredator behaviour which is known for several bird species. Generally this behaviour is considered consistent throughout the whole nesting cycle but there can be exceptions in some species. We found two switches in egg covering during nesting in grey partridge: the first between two early laying phases, the second between later laying and incubation. The clutch containing only the first egg remained uncovered, larger clutches were covered with dry vegetation in the laying period, but the eggs remained uncovered during incubation breaks. There was a strong consistency of this behaviour among females. From four tested factors, only nesting period significantly affected egg covering. We assume that the first uncovered egg may serve as a bait for predators to test nest-site safety whereas the motion in the course of egg covering during short incubation breaks may increase predator attraction.