BirdLife species factsheet for Madagascar Marsh-Harrier: http://www.birdlife.org/datazone/species/factsheet/22695368
Circus macrosceles is found only on Madagascar and the Comoro Islands. It has a broad distribution from the north to the south of Madagascar, but occurs only a low densities. Surveys in 2005-2006 of 71 % of the potential harrier habitat on the island recorded 80 individuals (Rene de Roland et al. 2009), while the population on Comoros (Grande Comore, Moheli and Anjouan: three separate subpopulations), where its habitat is nearly totally destroyed, is estimated at no more than 50 mature individuals (R. Thorstrom and L.-A. Rene de Roland in litt. 2007). The total population is now suspected to number fewer than 250 individuals (R. Thorstrom in litt. 2016), and is suspected to be in moderate decline on the basis of the loss and degradation of breeding habitat, persecution and disturbance.
This species had previously been listed as Vulnerable, but with an update to the current population size it would qualify as Endangered under criteria C2a(i) and D. This is because it has a very small population size, which is inferred to be undergoing a continuous decline and each subpopulation contains less than 250 mature individuals. We welcome any comments on this proposed uplisting.
De Roland, L.-A. R.; Thorstrom, R.; Razafimanjato, G.; Rakotondratsima, M. P. H.; Andriamalala, T. R. A.; The Seing Sam. 2009. Surveys, distribution and current status of the Madagascar Harrier Circus macrosceles in Madagascar. Bird Conservation International 19: 309-322.