Eurasian hobby density, nest area occupancy, diet, and productivity in relation to intensive agriculture

A Eurasian Hobby (Falco subbuteo) population of 13-18 breeding pairs was st udied for 6 years from 1987 to 1995 in a 62 km(2) study area located within the seasonal flood zones of the Po River plain in northern Italy and chara cterized by intensive farmland interspersed with poplar (Populus sp.) plant ations. Five percent of breeding attempts (n = 78 over the whole period) fa iled because of clear cutting of the nest tree and 4% because of human dist urbance associated with clear cutting of the nesting woodlot. Fledging succ ess was negatively related to laying date. Year after year, the nests of ea ch pair were found in restricted traditional "nest areas," but not all nest areas were occupied every year, even if suitable woodlots were available w ithin them. Occupation rate of nest areas was positively correlated with br eeding success. The nestlings' avian diet was dominated by Swifts (Apus apu s) and by Passer spp., accounting for 53 and 25%, respectively of 317 ident ified prey items. The local Eurasian Hobby population appeared to have adap ted fairly well to the intensively managed agroforestry system, with record ed density and productivity in the range reported for other European popula tions in less intensively cultivated areas. We did not detect any decline i n average density and productivity with increasing levels of agricultural c hange in various European populations. Possible reasons for this species' s uccessful reproduction in modern agricultural landscapes include timing of breeding, tolerance of habitat fragmentation and of human activities near t o the nest, tolerance of proximity to neighbors, type of diet, and absence of important predators.