Assessing the diet of Amur Falcon Falco amurensis and Lesser Kestrel Falco naumanni using stomach content analysis

The diets of Falco amurensis and F. naumanni were investigated by analysing the respective stomach contents of 64 and 22 individuals killed during a severe thunderstorm in December 2004. Interpretations of diet were made by considering (1) biomass of dietary items and (2) presence/absence of dietary items in the stomachs analysed. A single beetle (Coleoptera) species, cf. Heteronychus arator, made up the majority of stomach contents when using both methods. Other Coleopteran taxa did not comprise a significant proportion of the biomass in each stomach but were well represented in the stomachs of many individuals. Taxa less represented included Rodentia, Solifugae, Orthoptera, Hymenoptera and other unidentified prey items. Although both F. amurensis and F. naumanni sometimes feed on birds, we believe that all feathers found in stomachs were ingested during preening activities or were accidentally introduced during excision. The presence of a single beetle species in the diet of both species demonstrates the importance of episodic and/or predictable arthropod irruptions as a food source for these two migrant falcon species. Similarity in the stomach contents of both species indicates that both may face similar threats with regards to pesticide exposure, habitat alteration and persecution in their austral non-breeding range.