Population trends of the Madagascar Pond-heron between 1993 and 2016, the results!
Species classified globally endangered (EN) according to the IUCN, populations have been estimated between 2000 to 4000 individuals. This little heron only reproduces in 4 territories, Madagascar, Mayotte, Aldabra and Europa. Highly threatened, it is the subject of a first action plan that began in 2008, spread over 10 years, aimed at improving the knowledge and conservation status of the species in the various territories. Today, the time is in the balance through a scientific article published in 2020 in BioOne Complete and written by the associations Asity Madagascar, Durell Wildlife Conservation Trust, The Peregrine Fund Madagascar, GEPOMAY and the community of the French Southern and Antarctic Territories.
Significant census work
In order to be able to identify the Madagascar pond-herons colonies in the different territories, one of the first actions was to identify the different wetlands (lakes, marshes, rivers, mangroves and estuaries) in the 4 territories. Indeed, the Madagascar pond-heron feeds and nests in these wetlands.
Following this, on each territory, the monitoring of Madagascar pond-heron was carried out when possible from January to February, in full nesting peak in order to be able to observe the maximum number of individuals. In Madagascar and Mayotte, regular counts of waterbirds are carried out by local associations. All the areas previously identified were searched in order to gather different information: the number and location of individuals or nests of Madagascar pond-heron, the type of plumage or the threats. Winter counts were also carried out opportunistically in July-August in certain territories. On the French Southern and Antarctic Territories, the data were collected by conservation officer on the island of Europa since 2016.
Madagascar, main breeding site of the species
Between 1993 and 2016, Madagascar pond-heron were observed at 111 sites, including 106 in Madagascar, 4 in Mayotte and 1 in Europa. Data was also collected at Aldabra but the site could not be visited during this study. In Madagascar, 60% of the sites are located in the western part of the island, more favorable to the species.
With regard to nesting sites, 11 nesting sites were discovered in these territories between 1993 and 2016, including 6 in Madagascar (Tsarasaotra Park, Ambondrombe Lake, Tsimbazaza Park, Matsaborimena Lake, Lake Sofia and Lake Ravelobe), 4 in Mayotte (Ambato lagoon, Mangrove of Chiconi Mangajou, Ironi Be and Poroani Malamani) and 1 in Europa (Mangrove of Europa). In 2001, 20 to 50 pairs of Madagascar pond-heron were also observed in Aldabra.
In Madagascar, Madagascar pond-heron in breeding plumage have been observed on 100 other sites without showing signs of nesting. These sites were thus considered as potential breeding sites for the species, especially since some could not be prospected during the breeding season due to the major floods in the rainy season.
77% of the world population of Madagascar pond-heron is present in Madagascar. The results of the census work estimate the respective size of the populations at 812 birds in breeding plumage on Madagascar and 250 on Mayotte and Europa, that is to say 1062 breeding individuals on the whole of the territories.
By studying two of the largest nesting sites present in Madagascar, the park of Tsarasaotra and the park of Tsimbazaza, we observe respectively a decrease of 63% and 80% of the populations on these sites between 1990 and 2009. In addition, on the Island, 4 breeding sites identified between 1994 and 2003 seem to have been abandoned between 2007 and 2016.
In Madagascar, the populations observed each year vary widely, which may be the consequences of anthropic pressure, predation and the availability of the nesting site.
On the island of Aldabra, a few individuals had been identified in the 1970s while in 2001, a population of between 20 and 50 pairs had been observed there, which would show some notable increase on this island.
In Mayotte and Europa, there is not yet enough data but it would seem that the population on the island of Mayotte is increasing since 20 couples were identified in 2003 and 121 couples in 2015 but it is difficult to determine if this is due to an improvement in population dynamics or a better monitoring effort.
Of the 11 known nesting sites, the main threats identified are poaching of eggs and chicks and human disturbance. 77% of the sites presented cases of poaching while 23% were affected by fires or impacted by the predation of certain species.
Habitat destruction is a major threat. In Lake Sofia, Madagascar, more than one hectare of papyrus was burned for rice cultivation in October 2015. In Mayotte, many marshes have been converted to banana and taro cultivation. Urbanization in Madagascar has also led to the plowing of certain wetlands such as rice fields in Madagascar, used as a feeding site by the Madagascar pond-heron.
In addition, cases of natural predation have been observed in Madagascar on eggs or chicks, in particular by birds such as the Madagascar Harrier-Hawk, Madagascar Harrier or the Peregrine Falcon.
The impact of the rat is suspected but has not yet been proven on the Madagascar pond-heron.
Finally, an observation of a Madagascar pond-heron and a Squacco Heron was made in January 1999 at Tsimbazaza park in Madagascar which may raise the hypothesis of a potential risk of hybridization.
For the future?
This study made it possible to evaluate the size and the evolution of the populations of Madagascar pond-heron and to identify the distribution area of the species as well as its different breeding sites.
New actions must be implemented to ensure the protection of the species:
– Conservation actions on breeding sites to reduce human disturbance
– Deployment of a solid education and awareness program
– Restoration actions on wetlands
– Support for alternative economic activities as sources of income for local populations
– Research on the bioecological needs of the species and extend studies on potential breeding areas
– Research on possible hybridizations
– Research on the island of Aldabra
LIFE BIODIV’OM program
Since 2019, a new action plan on the Madagascar pond-heron has been drawn up, making it possible to list many actions to be carried out to protect the species from 2019 to 2023 on the island of Mayotte. Part of these actions will be carried out within the framework of LIFE BIODIV’OM between 2018 and 2023 and will make it possible to meet the needs mentioned above, in particular in terms of conservation actions on reproduction sites, education and awareness, d restoration actions on wet meadows and research on the species.
To find out about the different actions implemented in Mayotte as part of LIFE BIODIV’OM: https://www.lifebiodivom.fr/en/especes/crabier-blanc/
To find out more: the original publication