Investigation published in Ardea

January 1^st, 2012

Gut bacterial loads in avian nestlings may be affected by factors such as climate, seasonality and brood size. There is no published information on this subject for wild birds, despite its potential importance for nestling welfare and growth. We studied the associations of these factors with abundances of two common gut bacterial types, enterococci and Enterobacteriaceae, in nestling Pied Flycatchers Ficedula hypoleuca in central Spain. To that end, we obtained faecal samples from 54 broods (102 nestlings) on day 7 and 13 after hatching, for detection and estimation of bacterial abundance. Enterobacteriaceae loads on day 7 were positively correlated with mean temperature during the preceding seven days and negatively correlated with rainfall and hatching date. The negative associations of Enterobacteriaceae loads with rainfall were only found for early broods, at low temperatures. Enterococci loads on day 7 were positively associated with mean temperature. On day 13, Enterobacteriaceae loads were negatively correlated with hatching date, while enterococci loads were positively correlated with mean temperature. Enterobacteriaceae are apparently more sensitive to seasonal changes and climatic variation than enterococci, possibly in relation to variation in diet and nutrition. By contrast, enterococci are only sensitive to thermal variation. The attainment of full thermoregulatory capacity by nestlings reduces climatic effects on Enterobacteriaceae loads.

Gonzalez-Braojos S., Vela AI., Ruiz de Castaneda R., Briones V. and Moreno J.

Sources of Variation in Enterococci and Enterobacteriaceae Loads in Nestlings of a Hole-Nesting Passerine

	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).