This report was prepared for Marine Species and Threats team, Department of Conservation and did not form a part of the Conservation Services Programme.
The mixed-method census was carried out on the 27 July 2017 by Department of Conservation staff taking comprehensive aerial photographs of The Sisters and Motuhara at a range of scales. The number of Northern royal albatross chicks, adults and fresh carcasses were counted, and the numbers of Norther giant petrels present on the island prior to the start of breeding in August-September were also counted.
Overall, 2,116 royal albatross chicks were counted on the three islands. Seventy-eight adult albatrosses and 17 carcasses of recently dead chicks were also recorded, along with at least 1,889 Northern giant petrels, mostly concentrated on Motuhara (92%).
If little or no further mortality occurred among these chicks before fledging, breeding (nesting) success for the 2016/17 breeding season would be around 48% overall, considerably lower than the 64% recorded for the mainland colony on Taiaroa Head in the same season.
There were significantly greater numbers of feathery downed chicks, and fewer than expected well-feathered chicks on Motuhara. This difference could be due to peak breading on Motuhara being later than on The Sisters, or slower chick development on Motuhara, possibly reflecting segregated foraging areas for breeding adults from the two colonies.
If differences are due to asynchrony in peak egg laying, it may explain the 80% increase in Northern royal albatross occupying nest sites on Motuhara as seen on the 20 December, over the number counted 12 days earlier, and the 48% increase over the numbers counted on the 23 November. Counts of occupied sites on The Sisters were 15% lower than the number of pairs counted in November. This may explain the higher apparent breeding success on Motuhara.
Regular monitoring of this population is needed through aerial photography, and further marking and resighting of known-age birds to refine parameter estimates of demographic variables.