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The multidimensionality of behavioural defences against brood parasites: evidence for a behavioural syndrome in magpies?

Avilés, Jesús Miguel, Bootello, Eva María, Molina-Morales, Mercedes, Martínez, Juan Gabriel
Behavioral ecology and sociobiology 2014 v.68 no.8 pp. 1287-1298
Pica pica, brood parasitism, eggs, evolution, females, males, nests, parasites
Studies of antiparasite defences against cuckoo parasites have largely neglected the possibility that behavioural components of host defence may correlate giving rise to a behavioural syndrome. Furthermore, the different contribution of the host’s sex in nest defence has traditionally been disregarded. Here, we studied magpie (Pica pica) mobbing behaviour towards dummies of great spotted cuckoo (Clamator glandarius) and non-harmful hoopoes (Upupa epops) and egg rejection of parasite eggs in a population of colour-banded magpies. We predicted a positive correlation between the intensity of nest defence and egg rejection within each sex and that females respond more intensely than males to the threat of brood parasitism as they undertake incubation. Magpie males, but not females, defended their nests more intensely in those nests in which cuckoo model eggs were rejected. Individual magpies did significantly differ in their baseline level of nest attentiveness; however, there were no individual differences once pair identity was considered. Males and females defended their nests more intensely when it was exposed to the presence of a great spotted cuckoo dummy. Males, but not females, were more prone to appear at their nests, and females, but not males, were more prone to defend more intensely when their nests were challenged by a parasite threat. Our results thus agree with the view that mobbing behaviour and egg rejection in magpies may actually constitute a pseudosyndrome and highlight the necessity to integrate interindividual variation and the sex of the host in studies of the evolution of host defences.