Prey dynamics and breeding performance in a generalist predator: The differential role of prey density, biomass, and effective consumption rates

The breeding performance of predators is influenced by the differential consequences of prey density, prey biomass and effective consumption rates. Using camera traps at nests, we investigated whether changes in prey abundances caused functional and/or numerical responses of the common buzzard (Buteo) in a Mediterranean woodland region. After determining 1150 prey delivered to the nests by adults, we found that the biomass of prey caught was not a good indicator of its influence on individual life history traits such as productivity. Indeed, the consumption of small mammal prey, despite representing only 11% of the biomass delivered, had a much greater influence on buzzards' productivity than the consumption of snakes, which made up 47% of the biomass delivered. Live trapping evidenced that small mammals were roughly preyed according to its availability in the field, and their abundance in spring was directly related to buzzards' productivity and inversely related to hatching dates. Small mammals – mostly mice – can be considered as very suitable prey, owing quick handling times, profitability, and high energy intake. Our results pointed out the relevance of mice on buzzards' breeding performance, and altogether with the outstanding role of open-land small mammals on buzzards' demography during autumn-winter, suggested a key role of small mammals on buzzards’ ecology throughout the year cycle in the Mediterranean area studied. These findings have important implications for our understanding of the foraging strategies of generalist species and the role that habitat and environmental factors play in shaping them.