Monitoring selected forest bird species through aerial application of 1080 baits, Waitutu, New Zealand

Robust and reliable information is required to measure impacts of aerial 1080 operations on non-target bird species. We examined the impact on seven forest bird species of an aerial pest control operation using 1080 cereal baits to poison possums (Trichosurus vulpecula) within Waitutu Forest, Fiordland National Park. The survival of South Island kaka (Nestor m. meridionalis) and ruru (Ninox novaeseelandiae) was monitored using radio telemetry, and replicated bird counts within and external to the operational area were used to monitor changes in numbers of grey warblers (Gerygone igata), kaka, kereru (Hemiphaga novaeseelandiae), riflemen (Acanthisitta chloris), robins (Petroica australis) and tomtits (P. macrocephala). All radio-tagged kaka known to be present within the operational area prior to the application of toxic baits (n = 15) were alive 6 months later. None of the 11 radio-tagged ruru present during the operation died from 1080 poisoning. One ruru found dead (cached in a hole) following the application of toxic baits was tested for the presence of 1080, and none was found. It is likely that this bird was killed or scavenged by a predator. Transect counts of tomtits and grey warblers provided the largest sample sizes and most interpretable results. There was no evidence of any negative impact of 1080 for these species. Similarly, independent measures from point counts conducted annually since 2006 at two locations within the operational area also failed to highlight any declines in distribution or relative abundance attributable to the application of 1080 baits for six of the bird species monitored. We recommend (1) further pest control operations within the Waitutu area to prevent further deterioration in diversity and size of bird populations and (2) the continuation of monitoring programmes capable of assessing direction and rates of change in key demographic parameters for the bird populations living there.