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Summary
This report is part of the ongoing study of the tākoketai/black petrel (Procellaria parkinsoni) on Aotea/Great Barrier Island that began in the 1995/96 breeding season. During the 2025/26 breeding season, 491 tākoketai study burrows were intensively monitored within the Mt Hobson/Hirakimata study area on Aotea. The nine census grids held 204 of these study burrows, 121 of which were occupied by breeding pairs (59.3%) that produced 62 chicks - a breeding success rate of 51.2%. This is the lowest rate on record.
A total of 700 adults (164 newly banded) and 183 fledgling chicks were captured during the 2025/26 field season.
A total of 522 returned chicks has been recaptured at the colony over the course of the
study. Of these, 133 returned chicks were identified during the 2025/26 breeding season,
35 of which were caught for the first time. Not all cohorts were represented this season yet; this season had the highest number of cohorts represented (by at least one individual). Understanding the factors affecting return rates of chicks (e.g., survival vs imperfect detection) remains a challenge.
Intensive night surveys (between 2115 hours and 0515 hours) continued this season. The
percentage of banded tākoketai caught is marginally higher for intensive night surveys
(47.9%) than the ad-hoc surveys (45%). The percentage of returned chicks caught is
relatively higher for intensive night surveys (intensive 18.8%, ad-hoc 13.3%), as well as the number of banded tākoketai caught per survey (intensive n=5.3, ad-hoc n=2.1), and the number of returned chicks caught per survey (intensive 2.1 returned chicks/survey, ad-hoc 0.6 returned chicks/survey).
Two feral cat predation events, both in the South Forks area, and one rat predation event
were recorded in the study colony on Hirakimata this season. Introduced species still pose
a threat to the tākoketai population and it is imperative pest control measures continue.
WMIL recommends:
- That the standard population monitoring on Aotea continues with three visits (i.e., at egg-laying (Dec); at chick hatching/chick guard (late Jan/early Feb), and at chick
fledging (late Apr/early May) per season to track population trends. - That intensive night surveys continue to capture pre-breeders and returned chicks and improve recapture probabilities, ultimately improving juvenile survival estimates.
- That three additional census grids are added to the study area to increase the
proportion of the tākoketai population monitored on Aotea. - That the transect surveys across either the high-quality habitat (35-ha) around
Hirakimata or the entire the core tākoketai habitat (1000 ha around the summit) is
repeated to provide an updated land-based population estimate for Aotea. - That satellite tracking of returned chicks at the pre-breeding stage (age 3–5 years) be undertaken to determine foraging areas and risk around Aotearoa New Zealand waters.
- That genetic sexing of more tākoketai be undertaken to determine sex-related
differences in survival. In-depth modelling on the effect of age, age difference in pairs, and experience on breeding success to investigate senescence impacts in tākoketai.
Publication information
Bell, E., Maclean, C., Lamb, S., Ray, S. 2026. Key demographic parameters and population trends of tākoketai/black petrels (Procellaria parkinsoni) on Aotea/Great Barrier Island: 2025/26. Conservation Services Programme, Department of Conservation, Wellington, Aotearoa New Zealand. 39 p.