An analysis of the diet of Red-billed Chough Pyrrhocorax pyrrhocorax nestlings in NE Spain, using neck ligatures

Abstract

Owing to the scattered distribution and the difficulty of reaching their nesting places, Red-billed Choughs Pyrrhocorax pyrrhocorax still remain poorly known in many aspects of their biology and ecology, including diet . Previous diet studies for this species rely mainly on pellets and faeces, which are intrinsically biased food samples. We present data on nestlings' diet based on the analysis of undigested prey delivered to the nest by adults, gathered using neck ligatures . Atotal of 626 prey items belonging to 12 different taxonomic orders were collected from 63 ligatures. All food items found were animals, among them, the most important by numbers were Lepidoptera (caterpillars) and Coleoptera (also mainly formed by larval instars) . In terms of biomass, consumption of Lepidoptera was much higher than that of Coleoptera, though both form, also in this case, the bulk of the nestling's diet . Secondary prey items were Araneae, Orthoptera, Diptera, Hymenoptera and Gastropoda. The remaining prey categories can be considered accidental . According to typology, preys belonging to burrowers are those most collected by parent Choughs followed by walkers, hoppers, and the miscellaneous category others, constituted by accidental prey types . Three non-mutually exclusive factors are argued to explain differences among Chough diet studies: 1) the relative availability of food resources, 2) the highest energetic demand during the breeding season, and 3) the effect of biases associated with the different food samples analysed.