Investigation published in Biological Journal of the Linnean Society

August 1^st, 2011

Factors related to bacterial environment of nests are of primary interest for understanding the causes of embryo infection and the evolution of antimicrobial defensive traits in birds. Nest visitors such as parasites could act as vectors for bacteria and/or affect the hygienic conditions of nests and hence influence the nest bacterial environment. In the present study, we explored some predictions of this hypothetical scenario in the great spotted cuckoo (Clamator glandarius)–magpie (Pica pica) system of brood parasitism. Great spotted cuckoos visit the nests of their magpie hosts and frequently damage some of the host eggs when laying eggs or on subsequent visits. Therefore, it represents a good system for testing the effect of nest visitors on the bacterial environment of nests. In accordance with this hypothesis, we found that the bacterial load of magpie eggshells was greater in parasitized nests, which may suggest that brood parasitism increases the probability of bacterial infection of magpie eggs. Moreover, comparisons of bacterial loads of cuckoo and magpie eggs revealed that: (1) cuckoo eggshells harboured lower bacterial densities than those of their magpie hosts in the same nests and (2) the prevalence of bacteria inside unhatched eggs was higher for magpies than for great spotted cuckoos. These interspecific differences were predicted because brood parasitic eggs (but not host eggs) always experience the bacterial environments of parasitized nests. Therefore, the results obtained in the present study suggest that parasitic eggs are better adapted to environments with a high risk of bacterial contamination than those of their magpie hosts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 836–848.

Soler JJ., Peralta-Sanchez JM., Martinez-Bueno M., Martin-Vivaldi M., Martin-Galvez D., Vela AI., Briones V. and Perez-Contreras T.

Brood parasitism is associated with increased bacterial contamination of host eggs: bacterial loads of host and parasitic eggs

	Servicio de Identificación y Caracterización Microbiana (ICM). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).
	Departamento de Ecología Evolutiva. Museo Nacional de Ciencias Naturales (MNCN). Consejo Superior de Investigaciones Científicas (CSIC).
	Grupo de Coevolución. Consejo Superior de Investigaciones Científicas (CSIC).
	Departamento de Microbiología. Facultad de Ciencias. Universidad de Granada (UGR).
	Departamento de Biología Animal. Facultad de Ciencias. Universidad de Granada (UGR).