A full census of Northern Buller’s Mollymawk across both islands recorded 3,273 nests, of which 3,158 showed evidence of breeding this season (753 nests on Te Awanui/ Middle Sister and 2,520 on Rangitautahi/ Big Sister). In 2016 a total of 16,764 breeding pairs were recorded on Motuhara, giving a total breeding population for the Chatham Islands of 20,000 pairs; slightly higher than previously published estimates for the species. A census of Northern Royal Albatross recorded 2,388 nest sites, including 2,255 nests which showed evidence of breeding this season (864 on Te Awanui/ Middle Sister and 1,391 on Rangitautahi/ Big Sister).
Combining the results of last year’s research and additional aerial counts (2016-2017) it is possible to investigate the population trends. Determining the total population and population trend of Royal Albatross is problematic due to the biennial breeding behaviour. However, both the annual number of breeding pairs and the total breeding population indicate that the population is in decline, and that this decline is most significant on Motuhara. The causes for the decline are unknown, but may be related to 15 years of low productivity on Motuhara following the 1984 storm which stripped the island of vegetation and soil.
A complete count of both islands recorded 47 Northern Giant Petrel chicks on Little Sister and 20 chicks on Rangitautahi/ Big Sister. Applying a correction factor, using breeding success calculated from Rangitautahi/ Big Sister, the breeding population on Rangitatahi is estimated to be 156 breeding pairs (110 pairs on Te Awanui/ Middle Sister and 46 breeding on Rangitautahi/ Big Sister). In 2016 a total of 1,977 breeding pairs was estimated on Motuhara, giving a total breeding population for the Chatham Islands of 2,150 pairs; similar to previously published estimates for the species.
Bell, M.m Bell, D., Boyle, D. and Tuanui-Chisholm, H. 2018. Rangitatahi Seabird Research: December 2017. Technical report prepared for the Conservation Services Programme, Department of Conservation, . 27 p.