Breeding Season Diet and Prey Selection of the New Zealand Falcon (Falco novaeseelandiae) in a Plantation Forest

Abstract

We studied the diet of the endemic New Zealand Falcon (Falco novaeseelandiae) in a pine plantation forest by identifying species occurring in pellets and prey remains collected from 37 nest sites during the 2003 and 2004 breeding seasons. We assessed bird species abundance along transects in different-aged pine stands and along stand edges. Diet and prey abundance were compared to determine whether birds were taken disproportionately or in proportion to their abundance in the environment. Birds composed the greatest proportion of the diet, 84% by frequency and 74% by biomass. Common Chaffinches (Fringilla coelebs) were taken most frequently, but Eurasian Blackbirds (Turdus merula) and European rabbits (Oryctolagus cuniculus) contributed more by biomass, although rabbits were not recorded at every nest site. Bird density increased significantly with stand age but was highest along stand edges. Chaffinches were the most abundant species and taken in proportion to their availability. Species that occurred in open habitat (e.g., Yellowhammers [Emberiza citrinella]) or were of medium size (e.g., blackbirds) were taken more than expected based on their availability. Very small species (e.g., Grey Gerygone [Gerygone igata]) were taken in lower proportions than expected from their abundance. Proportions of bird species preyed upon were correlated most closely with bird species abundance in young pine stands (P = 0.02, r2 = 0.52). In a pine plantation habitat, New Zealand Falcons took primarily the more abundant species, those intermediate in size (16–160 g), and those frequenting open habitat.