Diet composition and prey choice of New Zealand falcons nesting in anthropogenic and natural habitats

In a biodiversity conservation exercise a native raptor has been reintroduced to Marlborough, a wine-growing area in New Zealand’s South Island, on the assumption that the abundant passerines attracted to the grapes will provide a natural food resource for this predator. As part of a study to assess the value of vineyards as habitat for the threatened New Zealand falcon (Falco novaeseelandiae) we used remote videography and prey remains to compare the diet composition of falcons nesting in a vineyard-dominated landscape with that of falcons nesting in natural habitat in nearby hills. We also quantified the abundance and species composition of avian prey in the habitats surrounding each falcon nest. Generally there were more birds in the vineyards but the composition of available prey did not differ between vineyards and the nearby hills, nor did the composition of avian species in the breeding-season diet of falcons. Avian prey was the main food source for falcons during the breeding season, representing 97.9% of prey items by frequency and 83.3% of prey items by biomass. Mammals represented only 1.9% of prey items by frequency, but made up 16.7% of prey items by biomass. We also found that falcons preyed on introduced species more than would be expected, and on endemic species less than would be expected, based on their availability in the landscape. The absence of any significant differences in diet between native and vineyard habitats during the breeding season suggests that the latter may be a suitable alternative when natural habitats are unavailable, although further study must be conducted into the role of supplementary feeding on these effects. These findings pave the way for research in other production landscapes that could be used for conservation measures.