An assessment of the diet of nestling Stonechats Saxicola torquata using compositional analysis

Abstract

Capsule Coleoptera (beetles), Hymenoptera (sawflies, ichneumon flies, bees, wasps and ants), terrestrial larvae (moth, sawfly and beetle) and Arachnida (spiders and harvestmen) accounted for 81% of Stonechat nestling diet. Aims To identify the main invertebrate taxa and composition in nestling diet and the possible influences on these of nestling age, site and temporal changes. Methods A total of 182 faecal sacs were collected from one or more visits to 55 broods in study areas around Cork Harbour, southern Ireland. Minimum estimates of the proportions of the number of invertebrate prey in each taxon identified were determined for each faecal sac and brood. Compositional analysis was used to test for age, site and temporal related differences in nestling diet. Results Nestlings were fed an exclusively invertebrate diet with a total of 1557 prey items identified from all samples. Coleoptera, Hymenoptera, terrestrial larvae and Arachnida accounted for 81% of the nestling diet. There were no age-related differences detected in the diet composition of nestling faecal sacs. Nestling diet did not vary significantly with study site, month or year. Conclusions Despite the lack of temporal, site or age-related variation in nestling diet, the taxa recorded in this study show a wide range of invertebrates.