Pāteke (Anas chlorotis) population trends in response to predator control on Great Barrier Island and Northland, New Zealand

Abstract

ABSTRACTPāteke, brown teal (Anas chlorotis) were until recently restricted to two key strongholds in northern New Zealand: Great Barrier Island and eastern Northland. In 2000, we applied predator control at two sites within the strongholds. We analysed three decades of summer pāteke flock count data collected at ‘trapped’ and ‘untrapped’ locations to assess numerical pāteke response to predator control. Using piecewise regression, we found that Northland pāteke at trapped sites increased from 130 individuals before predator control, to 341 by 2015. Conversely, pāteke in untrapped areas in Northland remain low. Compared with the Northland trapped site, there was a slower rate of population increase in the predator treated site at Okiwi on Great Barrier Island; 286 individuals at trapped sites before predator control and 390 individuals in 2015. Pāteke numbers at untrapped sites on Great Barrier Island also increased, from 214 to 316 individuals. Cause of death analyses confirm that predation is a significant factor at trapped sites in Northland (87% of pāteke deaths) and Okiwi (56% of deaths), with starvation accounting for an additional 16% of identified causes of death at Okiwi. Access to sufficient food sources may be limiting at Okiwi, but overall the provision of predator control has benefitted pāteke populations.