Testing assumptions of a supplementary feeding experiment aimed at suburban House Sparrows Passer domesticus

CapsuleEmpirical support is provided for the design and field methods associated with a replicated supplementary feeding experiment. AimsWe tested assumptions associated with a supplementary feeding experiment in which counts of House Sparrows were used to infer impacts of feeding mealworms and seed on reproductive output and population size. MethodsSupplementary food was provided at 33 House Sparrow colonies spread across suburban London, with 33 unfed colonies serving as controls. We compared the characteristics of fed and unfed colonies and tested whether competition for mealworms increased with colony size. We tested whether counts of young sparrows reflected variation in reproductive output and whether supplementary feeding affected the distribution of young sparrows. ResultsFed and unfed colonies were similar with respect to habitat, cat density, background feeding and initial colony size. Intensity of feeder usage increased with colony size. Counts of fledglings and juveniles were positively correlated with counts of active nests. Supplementary feeding influenced the distribution of juveniles but not that of recent fledglings. ConclusionsFed and unfed colonies were similar in character. Competition for mealworms was greater at larger colonies and fledgling counts provided a useful measure of variation in reproductive output across colonies.