Baseline Seabird Study on Tetiaroa

We continue our work to better understand the ecology of seabirds at Tetiaroa in relation to removal of rats from the island. This incudes collecting data on nesting success, nest density, and activity of seabirds, long-term survival of seabirds, and foraging ecology of seabirds.

Principal Investigators: Beth Gardner, Sarah J. Converse, Jayna DeVore, Eve M Hallock, Amelia J. Duvall
Affiliations: University of Washington, Université de Polynésie Française
Project Dates: January 2021 – long term

Update July 2025 : Baseline study of seabird populations on Tetiaroa atoll

This program aims to better understand the seabirds of Tetiaroa: where they live, how they use the different motu, how many there are, and whether they succeed in reproducing.

For this, several tools are used:

rings to track certain birds individually,
field counts to estimate their number,
sound recorders to detect their presence even when they are not visible, and
GPS tags placed on the brown boobies to know where they go to look for food around Tahiti, Moorea, or even further afield.

This monitoring allows us to better understand the health of Tetiaroa's seabird populations and the links between terrestrial and marine areas.

Summary of field activities

During the mission from May 12 to 21, 2025, two people carried out several activities on the motu, with work concentrated on Tahuna Iti, Tiara’aunu and Horoāterā.

The main actions were:

the installation of new GPS tags on brown boobies,
verification of sound recorders already installed on all motu,
brown booby nest counts along a 1 km transect at Horoāterā (noting eggs, chicks, etc.),
the installation of 5 cameras on the nests, to discreetly monitor reproduction.

Days were spent entirely in the field, often on foot or by kayak, and evenings were spent recharging equipment, backing up data, and preparing for the next day. The logistical support of the Tetiaroa Society was essential to the success of this mission.

Impacts and preliminary results

Analyses are still ongoing, but several initial results are encouraging:

It appears that the El Niño phenomenon has an effect on the breeding success of brown boobies and on the number of red-footed boobies nests, which confirms expected hypotheses GPS data shows that some brown boobies regularly feed around Tahiti and Moorea, which will soon be explored in more detail using statistical models. ·

Two notable observations: a brown booby was tracked to Ra’iātea, another to Mai’ao, showing the great mobility of these birds.

The program will continue with the same tools and methods (ringing, GPS, acoustics, counts, nest monitoring).

It is also planned:

to extend GPS tracking to other species, such as certain terns,
to launch the complete analysis of sound recordings collected since 2019, to better understand long-term trends in the presence and activity of seabirds in Tetiaroa

Baseline study of seabird populations on Tetiaroa atoll

In 2023, we continued our work to better understand the ecology of seabirds at Tetiaroa in relation to removal of rats from the island. This incuded collecting data on nesting success, nest density, and activity of seabirds, long-term survival of seabirds, and foraging ecology of seabirds. We collected data on nesting success of Brown Boobies for 6 months (January – June) using remotely triggered cameras and visual observations on 505 Brown Booby nests to determine the rate and, when possible, cause of nest failure. Data shows that storm swells and rats were the leading causes of nest failures prior to rat eradication.

To determine the relative activity of seabird species, we maintained 41 acoustic recorders that record audio each hour across the atoll. We banded 121 individual birds in order to provide long-term identifications and in October, we placed GPS tracking units on 12 Brown Boobies nesting on Tahuna Iti.

Figure 2: GPS recorded tracks for 11 tagged Brown Boobies from October - December 2023 are shown, each panel is an individual bird. All individuals but one (78524C19) were recorded making southern trips to Moorea and/or Tahiti.