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| The Aquatic Warbler
Acrocephalus paludicola
is one of the most threatened Western Palearctic
passerine species, classified as globally Vulnerable. With its breeding grounds relatively
secure, a clear need remains for the monitoring and protection of the migration and
wintering grounds of this rare and endangered migrant. Recent research has shown that the
Aquatic Warbler migrates through northwest Africa in autumn and spring. The wintering
grounds are apparently limited to wetlands of sub-Saharan West Africa, with records from
only about 20 localities in Mauritania, Mali, Senegal and Ghana. Given the lack of knowledge
of its whereabouts, we decided to use the available data to predict the wintering distribution
of the Aquatic Warbler with the help of Geographic Information Systems (GIS). We used
a novel approach to model the distribution of rarely recorded species, which is based on a
combination of presence-only and presence–absence modelling techniques. Using the
program BIOMOD, we thus generated four progressively more conservative predictions of
where the Aquatic Warbler overwinters in Africa. Whereas the most permissive model
predicts the Aquatic Warbler to be found in a latitudinal band stretching from the Senegal
river delta all the way to the Red Sea coast, the most restrictive model suggests a much
smaller area concentrated within the regions around the Senegal river delta in northern
Senegal and southern Mauritania and around the Niger inundation zone in southern Mali
and eastern Burkina Faso. Such model predictions may be useful guidelines to focus further
field research on the Aquatic Warbler. Given the excellent model predictions in this study,
this novel technique may prove useful to model the distribution of other rare and endangered
species, thus providing a means to guide future survey efforts. | |
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