Oriental reed warbler (Acrocephalus orientalis) nest defence behaviour towards brood parasites and nest predators

Abstract

Brood parasites and predators pose different threats to passerines that may favour the evolution of enemy-specific defence strategies. Furthermore, potential sex-specific variation in parental investment may be manifested in differences between male and female nest defence behaviour. We investigated these hypotheses in Oriental reed warblers (Acrocephalus orientalis), by recording sex- and stage-specific (nests with eggs or nestlings) responses to stuffed dummies placed at their nests. Warblers showed the highest level of aggression to the co-occurring parasite, the common cuckoo (Cuculus canorus), colour morph (grey), but showed reluctance to mob or attack the co-occurring nest predator, the magpie (Pica pica). There was a sex difference in rate of body attacks towards rufous morph common cuckoo, sparrowhawk (Accipiter nisus) (locally absent parasite and predator, respectively) and the spotted dove (Streptopelia chinensis) (locally present, harmless species), with females showing better ability to distinguish between these species than males.