In May 2025, a quarterly seabird survey was conducted over approximately 35 km of transects covering the atoll's 11 motu (excluding the hotel area). Observations included counting nests, eggs, chicks, juveniles, and adults, as well as the types of trees used for nesting. Checks were also carried out on the rings present on certain individuals, particularly brown boobies, and the data were transmitted to the University of Washington.
A set of camera traps was maintained to monitor the breeding of white terns, brown noddies, great crested terns, grey-backed terns, frigate birds, and masked boobies. An additional camera was installed on a new masked booby nest, allowing for a fourth successful hatching since rat eradication. Brown boobies were captured in partnership with an international research team to be ringed, measured, and fitted with tracking tags.
Feathers and eggshells were collected from dead and newly hatched birds. These samples were sent for isotopic analysis (nitrogen, carbon) and to measure mercury levels, as part of a study on the contamination of marine predators worldwide.
Monitoring of land crabs was carried out along the transects, with a daytime count of visible individuals and observations of their feeding or reproductive behavior.
Finally, a study of tahinu (Heliotropium arboreum) was continued at 20 sites across the atoll. Measurements included leaf growth, leaf replacement, herbivory rates, and herbivorous insect density. These surveys were conducted by a master's student from the Bordeaux School of Agronomy.
Preliminary results
Several notable observations were made during this mission:
- A fourth masked booby birth has been confirmed, again at the same nesting site.
- Ghost crabs have been heard calling in their burrows, a rare behavior that has been little studied, and the conditions of its occurrence (moon, time, season, etc.) are currently being thoroughly documented.
- An unprecedented nesting phenomenon of grey-backed terns has been observed, with several dozen pairs settling in at the same time. Unfortunately, these colonies have settled in an area exposed to swell and disturbances caused by visitors.
- A strong presence of birds was observed, much greater than in the previous two years. After the disruptions linked to an epidemic (2023) and El Niño (2024), this season could represent a return to favorable conditions.
The terns are thriving on Tetiaroa
The new images from the camera traps should provide a better understanding of the breeding behavior of crested terns and grey-backed terns, two species that are still poorly documented on the atoll.
Monitoring of bird and crab populations will continue quarterly, with missions planned for August and November 2025. Monitoring of the breeding success of seabirds will be maintained using camera traps.
In July 2025, capture-mark-recapture sessions will be conducted on ghost crabs to study the evolution of their populations and their morphological characteristics since the eradication of rats. Similar operations are planned for hermit crabs to estimate their densities and observe the exchange of shells between individuals depending on the site. A detailed characterization of the habitat will also be carried out on the 350 transects used for bird monitoring over the past four years. This step will provide a better understanding of the species' preferences for nesting trees.
