Habitat features and human presence as predictors of the abundance of shorebirds and wading birds wintering in the Gulf of Gabes, Tunisia

Understanding ecological factors and processes affecting waterbird abundance is a major question in ecology and important for conservation purposes. In the Mediterranean, studies dealing with the determinants of waterbird abundance and distribution have mainly been concerned with European coastal habitats, whereas less attention has been paid to coastal areas in North Africa. In this work, we used count data to investigate the relevance of habitat features and human presence as predictors of the abundance of shorebirds and wading birds wintering in the Gulf of Gabes, a particularly important wintering quarter for many Palearctic waterbirds in Tunisia. We found that the strength and direction of the relationships between bird abundance and both habitat and human parameters varied among species, depending on their ecological requirements. Most species occurred more abundantly in large mudflats compared to narrow sandy beaches, while one species showed an opposite trend. We also found that the studied sites were frequently visited by local people, mainly for clam harvesting, thus sharing the intertidal habitats with birds. However, the abundance of most species did not decrease with increasing human presence, suggesting that traditional clam-harvesting activity did not seem to disturb birds. Nonetheless, we believe that further investigations of the interactions between birds and clam-harvesters are needed to better understand the role of traditional clam-harvesting activity in shaping the abundance and diversity of waterbirds wintering in the Gulf of Gabes.