Modelling habitat suitability in the Aquatic Warbler wintering ground Djoudj National Park area in Senegal
AbstractThe only well-studied wintering ground of the globally threatened Aquatic Warbler Acrocephalus paludicola is the ‘Djoudj area’ in Senegal. This study identifies potential Aquatic Warbler habitats within that area and gives an estimate of the size of the local wintering population. A land-cover map was generated by classifying high-resolution satellite images. Overlaying it with presence–absence data from field surveys and using logistic regression models (GLMM), we derived the presence probability of the Aquatic Warbler in the study area. Using presence probability as a proxy of habitat suitability we identified 4 729 ha of potential habitat. We calculated the population density of the Aquatic Warbler by applying a Poisson mixed model to our land-cover raster data and estimate a total population size of 776 individuals (range 260–4 057), i.e. 0.37–19.8% of the world population. However, this estimate is complicated by uncertainties including the unknown efficiency of the bird-catching method, clumped presence of individuals, the variability of water levels and other seasonal changes. An effective management of Aquatic Warbler habitats in the Djoudj area should include extensive grazing, the control of litter accumulation and shrub growth, and the removal of plant material from the channels to improve water circulation.
Keywords: conservation, GLMM, habitat modelling, habitat prediction, wintering ground
OSTRICH 2014, 85(1): 57–66