Age-related changes in abundance of enterococci and Enterobacteriaceae in Pied Flycatcher (Ficedula hypoleuca) nestlings and their association with growth

Abstract

Bacteria have the potential to be important selective forces in the evolution of many aspects of avian biology, including nestling growth. We estimated abundances of two common gut bacterial types in birds (enterococci and Enterobacteriaceae) and their correlation with growth in tarsus length, mass and wing length of 102 nestlings (54 broods) of the Pied Flycatcher, Ficedula hypoleuca, in a population of central Spain. Chicks were weighed and measured on days 7–13 after hatching, at which ages fecal samples were obtained for detection and estimation of abundance of enterococci and Enterobacteriaceae. The loads of the two bacterial types were not correlated. Enterobacterial loads decreased from day 7 to 13, while loads of enterococci increased during the same period. On day 7, loads of Enterobacteriaceae among nest mates were similar whereas loads of enterococci were not similar. On day 13, nest mates did not have similar loads of either bacterial type. Loads of enterococci were positively correlated with body mass and wing length on day 7, but not on day 13. Tarsus growth between days 7 and 13 was negatively correlated with loads of enterococci on day 7.