Update on what birds the eradication team have been monitoring
Written by Stephen Horn – Project Manager
Members of the Antipodes Mouse Eradication project have been working to document native flora and fauna both before and after the application of rodent bait to eradicate mice to better understand the impact that mice have had on these endemic and native communities. The information gathered will complement baseline studies started in 1996 to document the changes of these communities in response to the absence of mice if the eradication has been successful.
Monitoring of ground-bird populations has been conducted using distance sampling techniques “before” and “after” the eradication attempt. Mice are competitors for seed and invertebrate resources that ground-birds rely on. Mice are also believed to prey on nestlings and or eggs of some ground and sea bird species. Distance sampling methodology for native ground birds is accomplished by traversing the island along pre-established transects observing the visual presence of four endemic ground bird taxa: Antipodes Island Parakeet (Cyanoramphus unicolor), Reischeck’s parakeet (Cyanoramphus hochstetteri) Antipodes Island Snipe (Coenocorypha aucklandica meinertzhagenae) and Antipodes Island Pipit (Anthus novaeseelandiae steindachneri) which are endemic subspecies. The monitoring team cover a variety of terrain while conducting the transects; from relatively flat tundra-like moss and lichen dominated plateau to literally swimming through head height grasses, sedge and ferns on hillsides and lower wetland areas. At the beginning of each transect, environmental conditions are recorded as the conditions have an effect on the frequency of encounters particularly when it is too windy. Some days bring blue clear skies and light winds (rare) and others windy conditions with scattered hailstorms and rain!
Snipe are cryptic creatures. Encounters with them are relatively rare on the Antipodes compared with other Subantarctic Islands, such as Adams Island in the Auckland Islands Group and Campbell Island where no rodent pests exist. Every snipe seen is recorded against the person hours spent in the field. Snipe are expected to increase in abundance on Antipodes Island with the removal of mice and the affect of their activities. The encounter rate of snipe will complement monitoring started in 2012 and will continue as part of the post-eradication monitoring activities.
Twenty five Antipodes Island pipits were captured and banded for short-term identification with plastic bands of varying colour combinations within the vicinity of the Hut Cove, Reef Point, Anchorage Bay and Stella Bay, near the field camp. A daily route is walked through this area and sightings recorded in order to track survival before and after the application of bait. The results provide an understanding of the short term impacts of baiting on the pipit population as some pipits were found to feed on the bait during winter trials in 2013. Preliminary results have identified some banded pipits that have disappeared since baiting. However, observations remain frequent and transects along coastal strongholds show good numbers of pipits are present, which is a reassuring result. Sustainable populations also exist on the offshore islands which weren’t baited where we were confident mice were not present (Bollons Island and the Windward Islands) providing the required insurance in case losses were higher than expected.
Banding Albatross Chicks
Monitoring for the endemic Antipodean wandering albatross (Diomedea antipodensis) has been undertaken on an almost annual basis since 1994 to track survival, productivity, recruitment and on a more extensive basis, the extent of this bird’s feeding grounds. The team here has contributed to this work by assessing the chick survival in the study area. We have also done work to utilise helicopter based aerial photography paired with GIS in an attempt to conduct a population census as Antipodean albatross chicks are present and being fed over the winter, easily visible on nest mounds from the air. The only other seabird breeding over winter is the Grey petrel. Young albatross chicks in a study area on the North Plains have also been banded for identification prior to them fledging late in the year, allowing their survival to be tracked over the years.