Protecting threatened Over-seas biodiversity

Six Madagascar pond herons fitted with GPS trackers: a world first

In late November and early December 2019, The Association for the Study and Protection of Birds in Mayotte (Groupe d’Etudes et de Protection des Oiseaux de Mayotte, GEPOMAY)  carried out a mission, in collaboration with a team of experts, to capture and fit tracking equipment to Madagascar pond herons, a first on a global level.

Madagascar pond herons equipped with a tag ready to be released © Alexandre LAUBIN/LPO

 The Madagascar pond heron

 The Madagascar pond heron, Ardeola idae, is a small beige-brown heron striped with black, which during the breeding season has white plumage and a vivid blue beak. This very timid species breeds only on four islands in the world: Madagascar, Aldabra, Europa and Mayotte. Mayotte is the second most important breeding site in terms of numbers (182 pairs in 2018). The species is classed as “endangered” on the global red list (EN, IUCN) and “critically endangered” on the French red list (CR, UICN). In Mayotte, the species is threatened by the loss and degradation of the wetland habitats where it feeds and nests, by human disturbance, and by the poaching of chicks and eggs. The predation of eggs and young by rats is suspected but remains unproven.

Identifying the feeding areas of the species

Currently there is very little available data on the Madagascar pond heron and few studies have been carried out, despite the unfavourable conservation status of the species. The mission undertaken at the end of 2019, which will be followed by further missions in 2020 and 2021, makes it possible to equip a total of 15 birds with GPS transmitters in order to improve knowledge of the ecology of the species. It will answer the following questions:

  • Does the Madagascar pond heron feed in specific areas that need to be better managed or conserved?
  • Do individuals from the same colony all feed in the same location or in different areas? Does each individual remain in the same feeding sites over time?
  • During the breeding season, what is the size of the Madagascar pond heron’s territory?
  • Outside the breeding season, what movements are there at a local and regional level? Where do individuals leaving Mayotte migrate to during the dry season (March to August)? Do they return to Mayotte every year?

Specialists present for this world first

Because of the ground-breaking nature of the mission, a team of specialists supported GEPOMAY in order to ensure its success. The following people went to Mayotte to oversee operations to capture and equip the birds:

  • Alexandre LAUBIN

Manager of expertise and support for the LPO (Ligue pour la Protection des Oiseaux) in Franche Comté. A licensed bird ringer working for LPO France as part of the Life BIODIV’OM project, Alexandre has one and a half years of experience for GEPOMAY and two years in the French Southern and Antarctic Territories, places in which he worked in particular on the Madagascar pond heron. He has a broad knowledge of the breeding sites of the species and of the field conditions in Mayotte.

  • Loïc and Pierrick MARION.

Loïc, emeritus researcher for the National Scientific Research Centre at the University of Rennes 1, specialises in the ecology of piscivorous birds (Herons, Cormorant etc) and is also a member of the National Council for the Protection of Nature (Conseil National pour la Protection de la Nature, CNPN). His brother Pierrick is a young retiree from the Regional Directorate for Environment, Planning and Housing (Direction Régionale de l’Environnement, de l’Aménagement et du Logement, DREAL) for Nouvelle Aquitaine and also a holds a bird ringing license from the Centre for the Research into the Biology of Bird Populations (Centre de Recherches sur la Biologie des Populations d’Oiseaux, CRBPO). Together, they have been ringing herons for around fifty years in particularly difficult environments, and have equipped young Spoonbills with Argos tags and monitored adult Grey herons using radiotracking.


A Dutch researcher and bird ringer, Jan studies the habitat utilisation and migration ecology of water birds such as the Purple heron and Bittern. With considerable experience of capturing birds and fitting harnesses and GPS trackers, he has participated in several studies concerning wetland birds (in locations such as Benin, Ukraine and Russia), including studies of the movements of the Agami heron (Agamia agami) in French Guyana for the LIFE+ CAPDOM project.

The mission

 Madagascar pond herons breed in certain mangroves in Mayotte, building their nests in the tops of the mangrove trees that make up this environment. In order to equip them with tracking devices, the team of specialists, accompanied by the GEPOMAY team, captured a number of individuals.

The birds were captured in heronries found in the Ironi Bé and Chiconi mangroves. GEPOMAY and the team of specialists carried out substantial work in advance of the capture mission in order to test the equipment in real conditions and ensure its technical feasibility. This preparatory phase made it possible to study the behaviour of the species towards the devices and thus to improve the capture techniques that were to be implemented.

Each captured individual was fitted with a uniquely coded metal ring. Biometric measurements were taken (length of beak and wing, weight etc.) and then the bird was equipped with a GPS tracker held in place by a harness. This equipment includes a solar panel that recharges the battery and weighs under five grams, which is less than 3% of the total weight of the bird. The individual was then released immediately.

During this first mission to ring Madagascar pond herons in Mayotte, six individuals were successfully equipped with trackers in eleven days. The first attempts to collect GPS data using antennae have begun, and information on the movements of some individuals has already been received. Thanks to the efforts of the experts on this delicate mission, its objectives have been achieved! New capture missions will be scheduled over the coming years.


 The Association for the Study and Protection of Birds in Mayotte (Groupe d’Etudes et de Protection des Oiseaux de Mayotte, GEPOMAY) has been carrying out monitoring programmes since 2010 in order to increase understanding of the population and phenology of the Madagascar pond heron in Mayotte. The association also coordinates a national action plan for the species (2019−2023) and in 2018 incorporated a European programme, Life BIODIV’OM, which is managed nationally by the LPO and in Mayotte by GEPOMAY. The aim of this programme is to reduce the threats faced by the species: to combat poaching, to increase public awareness in order to reduce human disturbance, and to restore and protect its habitats.