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 studied for 6 years from 1987 to 1995 in a 62 km2 study area located within the seasonal flood zones of the PO River plain in northern Italy and characterized by intensive farmland interspersed with poplar (Populus sp.) plantations. Five percent of breeding attempts (n =78 over the whole period) failed because of clear cutting of the nest tree and 4% because of human disturbance associated with clear cutting of the nesting woodlot. Fledging success was negatively related to laying date. Year after year, the nests of each pair were found in restricted traditional ‘nest areas,’ but not all nest areas were occupied every year, even if suitable woodlots were available within them. Occupation rate of nest areas was positively correlated with breeding success. The nestlings’ avian diet was dominated by Swifts (Apus apus) and by Passer spp., accounting for 53 and 25%, respectively of 317 identified prey items. The local Eurasian Hobby population appeared to have adapted fairly well to the intensively managed agroforestry system, with recorded density and productivity in the range reported for other European populations in less intensively cultivated areas. We did not detect any decline in average density and productivity with increasing levels of agricultural change in various European populations. Possible reasons for this species’ successful reproduction in modern agricultural landscapes include timing of breeding, tolerance of habitat fragmentation and of human activities near to the nest, tolerance of proximity to neighbors, type of diet, and absence of important predators.

Fabrizio Sergio and Giuseppe Bogliani, The Condor 101:80~817