Substantial contribution of invertebrates to the diet of a winter seed‐eater,the reed bunting Emberiza schoeniclus,wintering in a sewage farm in south‐western Poland

We investigated whether the winter diet of a typical seed‐eating bird is hard‐wired in the context of evolutionary hypothesis for granivory. We examined the diet composition of ‘a small‐billed form’ of the reed bunting Emberiza schoeniclus wintering in a sewage farm in south‐western Poland (Central Europe), where unfrozen wastewater provides various groups of invertebrate prey. The analysis of droppings (N = 151) collected from four different feeding grounds located in reedbeds and grasslands inundated with waste‐water showed the substantial contribution of invertebrates in the diet of reed buntings. Across four sample areas, the frequency of invertebrates in faecal samples ranged between 37% to 80%. In total, we identified 194 animal prey, mainly spiders Araneae (53% of all identified invertebrate prey), and several taxa of Coleoptera (43%). Among plant food (N = 8357 identified items), the most numerous were shells of weed seeds, namely Amaranthus sp. (56.8%), Urtica dioica (22.6%), and Chenopodium sp. (19.6%). Our results showed that, during winter, the reed bunting is not an obligatory seed‐eater. This species may exploit both animal and plant food; hence, our results indicate that the reed buntings wintering in temperate Europe may feed more opportunistically than was previously assumed. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 429–433.