Egg pecking behaviour by shiny cowbird females

FIORINI VANINA D.; GLOAG R; COSSA NATALIA A.; REBOREDA, JUAN C.

Hainan

Simposio; International Symposium on Avian Brood Parasitism; 2012

China Ornithological Society

Shiny cowbird females peck and puncture host eggs when they visit their nests. In addition,they may also peck and puncture parasite eggs when the nest has already been parasitized, afrequent situation in common hosts of this parasite. We investigated whether the number andtype of eggs present in the nest influence egg-pecking behaviour. We video recorded 142visits by parasite females in four experimental groups of chalk-browed mockingbird (Mimus saturninus) nests: one or four host eggs and one or four parasite eggs and determined the number of pecks and eggs punctured and whether host agonistic behaviour affected these variables. The number of pecks per egg increased with number of eggs and it was higher in nests with parasite eggs while the number of eggs punctured increased with number of eggs and it was higher in nests with host eggs. Host agonistic behaviour reduced the number of pecks but not the number of eggs punctured. Experiments with parasite females in captivity showed that the number of pecks needed to puncture parasite eggs were higher than those needed to puncture small or large host eggs. We discuss factors that may influence frequency and intensity of pecking behaviour by female shiny cowbirds.