Validité de l'analyse des sacs fécaux pour l'étude du régime alimentaire des jeunes au nid de la linotte mélodieuse (Carduelis cannabina)

Abstract

Listen

Translate article

Diet was studied in nestlings of the European Linnet (Carduelis cannabina L.) by analysing fecal sacs, the only method that allows continuous sampling of the diet to the end of the nesting period. The validity of the method was tested by comparing the results of the analysis with the composition of the stomach contents of nestlings that died during nesting. This study was carried out in a moor surrounded by hedges, at Campénéac, in Brittany, France. There is a strong correlation between the mean composition of the fecal sacs and that of the stomach contents, but biases were found. Animal matter, which represents a minimal fraction of the food and is given only occasionally to the chicks during the first days of feeding, leaves practically no traces in fecal sacs. Moreover, a few species of seeds that are almost completely assimilated, e.g. Brassica napus and Euphorbia helioscopia, can be greatly underestimated in the analysis of fecal sacs. As these species may be at certain times the preferred food of the chicks, specific correction factors have been calculated to compensate for the biases. Our results indicate that by analysing the fecal sacs one can quickly identify and quantify the diet of nestlings and that with a relatively small number of samples; it constitutes therefore a reliable and rapid technique.[Journal translation]