Protecting threatened Over-seas biodiversity

The Reunion cuckooshrike under study in Reunion island

As part of LIFE BIODIV’OM program, the Society of Ornithological Studies of Reunion island (SEOR) and the Réunion National Park (PNRun) are carrying out various studies in order to learn more about the Reunion cucooshrike (called Tuit-tuit locally) and thus improve the effectiveness of future conservation actions to come.

Reunion cuckooshrike (Tuit-tuit) © Jaime MARTINEZ

Preparatory studies
In order to preserve the population of Tuit-tuit in Reunion island, one of the flagship actions of this program is to implement operations to strengthen the existing population and / or reintroduce individuals on a reception site to constitute a second population.

These different strategies require upstream to study the genetic structure of the current population, to study its dynamics but also to identify the areas of habitats favorable to the species for these possible releases.

Analyze the genetics of the species
Studies are being carried out to assess the diversity and genetic structure of the species. Preliminary results show that one of the population’s nuclei has slight genetic differentiation from the rest of the population. This genetic isolation is confirmed by the geographic distance of these individuals.

Now reflections are underway in order to identify the most appropriate strategy to save the species: should the maintenance of this genetic diversity intervene in the choice of possible areas for sampling and release of individuals?

Study population dynamics
Thanks to the monitoring of the reproduction of the species, Capture-Marking-Recapture (CMR) data with colored rings placed on the young before flight from the nest have been recorded for more than 15 years. Their analysis makes it possible to understand how the dynamics of this population works, and then to project the outcome of each scenario of sample / release of individuals. The scenarios test the effects of the sampling stage of individuals (chicks or adults), their number, the frequency of operations, and a set of predictable events linked to these manipulations, such as the ability of couples to produce an egg replacement if they were taken.
Knowing these different elements will allow us to better orient the operational strategies to adopt in the coming months.

Identify his favorite habitat
SEOR and PNRun worked together to model the areas of favorable habitat used by the Tuit-tuit. This modeling work makes it possible to understand from knowledge of the current and past distribution of the species, which areas close to its range can still accommodate new individuals, and which areas on the island scale present the same environmental characteristics. At the same time, field surveys were carried out to try to understand how certain variables of the environment encountered can influence the presence or absence of the species. These plots are characterized according to many criteria aimed at determining the procession of plant species and its vertical and horizontal structure which will support the choice of individuals’ release zones.

Determine the appropriate translocation method
In the world, in order to strengthen bird populations, many techniques are possible and conceivable, this is why a bibliographical synthesis on the existing protocols on this operation was produced by SEOR. The techniques are varied, some propose the removal of juveniles, others of chicks, in order to move them, while others require the detention, the breeding and sometimes even the reproduction in captivity of the birds before releasing them. It is a question of understanding what would be the technical and logistical feasibility best suited to the characteristics of the Tuit Tuit.

Thanks to all of these areas of investigation, with the support of partners and experts mobilized around this project, SEOR is currently developing the most suitable protocol for the preservation of the species.