A quantitative comparison of neck-collar and faecal analysis to determine passerine nestling diet

Two commonly used methods for diet determination, neck-collars (ligatures) and faecal analysis, were compared. Samples were collected from the chicks of three nidicolous species: Dunnock Prunella modularis, Yellowhammer Emberzia citrinella and Whitethroat Sylvia communis. As determined by the two methods, significant differences in diet composition were found for Dunnock and Whitethroat. For faecal samples compared with neck-collar samples, more Coleoptera and fewer Collembola were identified in Dunnock and more Coleoptera and Diptera in Whitethroat. For invertebrate diversify, analysis of faecal samples identified significantly more invertebrate groups in the diet for Whitethroat, while for Dunnock, neck-collars contained the greater diversity. No differences were detected between the two sampling methods for Yellowhammer in respect of either invertebrate groups or diversity. The relative value of these two methods is discussed.