Foveaux shag breeding population size

Published:  

July 2023
This is the final annual report for Part B (Foveaux shag) of POP2021-07: Otago/Foveaux shag breeding population, by Parker Conservation.

Summary

Endemic to Southern New Zealand, Foveaux shag Leucocarbo stewarti are classified as Threatened-Vulnerable, but there is little recent information on their population status and trends to inform conservation management. The aim of this project was to conduct a breeding population census of Foveaux shags. Eight current breeding sites were identified, and three sites that have stopped being used since the last breeding record.

Comprehensive surveys were conducted in targeted visits of current breeding sites. Aerial photographs for Foveaux shag counts were taken using a drone where appropriate (11 sites) or aerial DSLR photographs where a drone could not be flown (two sites). Building on animal response trials in previous work with shag species, these drone overflights during the breeding season first determined the drone flight height appropriate at each site to cause minimal disturbance. Survey flights were all taken within three days of each other, at the start of the breeding season in October 2022.

Photographs were counted for the number of Foveaux shags on nests. Since breeding starts earlier than October at some sites (breeding asynchronous), we expect to have missed some nesting attempts that failed before the survey, so figures should be understood as minimum breeding population estimates.

Results show breeding colonies ranged in size from two small colonies at Raratoka, with ~9 nests each, to the much larger colony at Fife Rock comprising some 275 breeding pairs (best estimate; range 273–277). The Foveaux shag population estimate—at least 1007 (1002–1012) breeding pairs at the start of the 2022 breeding season—is roughly similar to the last whole-population count in 2011. However, for assessment of population trends to be robust the population size estimate should be repeated.

Publication information

Rexer-Huber, K.; Parker, G.C. 2023. Foveaux shag population census. POP2021-07 final report for the Department of Conservation. Dunedin, Parker Conservation. 22 p.

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