Population assessment of White-capped Albatrosses Thalassarche steadi in New Zealand

ABSTRACT

White-capped Albatrosses Thalassarche steadi breed only on New Zealand’s sub-Antarctic islands, principally the Auckland Islands. The species is commonly caught as bycatch in global longline and trawl fisheries, and it has been estimated that 8 000 birds are killed each year. In December or January between 2006 and 2017 we undertook annual population censuses of the White-capped Albatrosses breeding at the Auckland Islands using aerial photography. Estimated annual counts for the three breeding sites were adjusted using estimates of the proportion of birds clearly not associated with an active nest (loafers), to estimate annual breeding pairs for each breeding season. The estimated mean number of annual breeding pairs in the Auckland Islands during this period was 89 846 with high inter-annual variability (range: 74 031–116 025). Over the 12 years of the study adjusted counts for all sites combined showed a negative linear trend but this relationship was not statistically significant. Similar analyses using TRIM classified the population as ‘stable’. Given the estimated number of annual breeding pairs and the high frequency of biennial breeding it is likely that fisheries bycatch, if it has been estimated accurately, is impacting this population. Continuation of annual monitoring is recommended to increase the precision of the estimated population trend and help determine if the high levels of bycatch across multiple fisheries are sustainable in the long term.

KEYWORDS:

• Aerial survey
• population trend
• seabird bycatch
• white-capped mollymawk
• conservation

Acknowledgements

The support of Susan Waugh, Martin Cryer and Nathan Walker of the New Zealand Ministry of Primary Industries, Richard Wells of the DeepWater Group, and Igor Debski and Pete McClelland of DOC during the early years of the project was greatly appreciated. We are also grateful for the efforts of Pete McClelland, Sharon Trainor, Doug Veint and Joseph Roberts for facilitating permits to visit and work in the Auckland Islands over the years. Photographic and logistical support was provided by Simon Childerhouse, Mark Holdsworth, Rachael Alderman and Luke Finley. Southern Lakes Helicopters and pilots Sir Richard ‘Hannibal’ Hayes, Mark Hayes, Mark Deaker and Chris Green safely transported us to and from the Auckland Islands and provided an excellent photographic platform for the study. We also thank Leigh Torres, Graham Parker and Kalinka Rexer-Huber of NIWA for conducting ground-truthing counts on South West Cape and Disappointment Island, Alistair Hobday, Claire Mason and Rachael Alderman for providing information on nest failure in Shy Albatrosses, and William Gibson of the Ministry of Primary Industries and the DeepWater Group Limited for project support in recent years. Comments from three anonymous reviewers and Richard Phillips improved the paper, and we are grateful to Kate Buchanan for managing the editorial process.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed at https://doi.org/10.1080/01584197.2022.2161915

Additional information

Funding

This project was funded by the Department of Conservation’s Conservation Services Programme, and the Ministry of Fisheries..