Diet Analysis of Wetland Passerine Nestlings Using Neck Collars or Faecal Sampling Produces Similar Results

Two methods are commonly used to study the diet of nestling passerines: the neck collar method and faecal sampling. Most studies apply either method, however, few methodological studies comparing both methods exist and are mainly limited to farmland birds. Furthermore, existing methodological studies only include high-level taxonomic diet categories. Here, we compared both methods using two wetland species, the Reed Bunting Emberiza schoeniclus and the Sedge Warbler Acrocephalus schoenobaenus, and included family level as a lower taxonomic prey level. We found no differences between the two methods in the dietary composition of high-level taxonomic categories (mainly orders) and only small differences in some orders at the family level. Hence, we recommend using the less invasive and easily accessible faecal sampling method rather than the use of neck collars in diet composition studies.