Wintering waterbird assemblages in the central part of the Gulf of Gabès in southern Tunisia

Hamza, F., Hammouda, A. & Selmi, S. (2016). Wintering waterbird assemblages in the central part of the Gulf of Gabès in southern Tunisia. Ostrich 87:  217–223. doi: 10.2989/00306525.2016.1207721


Although the Gulf of Gabès is recognised as an Important Bird Area, several aspects of the ecology of waterbirds inhabiting this area still need to be investigated. We observed how waterbird foraging guilds varied among habitats. In total, 49 species belonging to 16 families were recorded. Winter visitors accounted for 73% of counts. The avifauna was dominated by shorebirds (52% of records), followed by large wading birds (25%), open-water birds (18%) and waterfowl (5%). However, the structure of local waterbird communities and their composition in terms of foraging guilds varied according to habitat type. The bird communities of sandy beaches were dominated by open-water birds, whereas large mudflats were dominated by shorebirds, and wadi estuaries showed a more even representation of foraging guilds. Locally rare species had narrow distributions, whereas locally abundant species were found widely within the gulf. For four species the 1% population level criterion of the Ramsar Convention was exceeded. Overall, our results show that the Gulf of Gabès hosts important numbers of waterbirds with different ecological requirements, which confirms the importance of this gulf as a wintering area for Palearctic waterbirds.

Rassemblements hivernaux chez les oiseaux aquatiques de la zone centrale du Golfe de Gabes en Tunisie méridionale

Bien que le Golfe de Gabes soit reconnu comme une zone importante pour la conservation des oiseaux, de nombreux aspects de l’écologie des oiseaux d’eau qui y vivent restent peu connus. Ainsi, l’objectif de ce travail était de décrire la diversité de l’avifaune hivernante dans ce golfe et d’étudier la variation de sa composition, en termes de guildes alimentaires, entre les différents types d’habitat qu’abrite cette région. Au total, 49 espèces appartenant à 16 familles ont été recensées. Les hivernants représentent 73% des effectifs enregistrés. Cette avifaune est dominée par les limicoles (52% des effectifs enregistrés) suivis par les grands échassiers (25%), les laridés (18%) et les canards (5%). Cependant, la structure des communautés locales et leurs compositions en termes de guildes varient en fonction de d’habitat. C’est ainsi que les avifaunes des plages sableuses sont dominées par les laridés, celles des vasières par les limicoles, alors que les estuaires des oueds abritent une avifaune plus équilibrée. Les espèces localement rares ont une répartition restreinte, tandis que les espèces localement abondantes ont une large distribution dans le golfe. D’autre part, pour quatre des espèces recensées, le critère de 1% de la Convention de Ramsar est atteint. Globalement, nos résultats montrent que le Golfe de Gabes abrite un effectif important d’oiseaux d’eau ayant des affinités écologiques variées, ce qui confirme l’importance de ce golfe pour l’avifaune Paléarctique.

Eurasian Spoonbill, Spatule blanche (Platalea leucorodia) ringed in The Netherlands and observed here in gulf of Gabès, Tunisia.

Eurasian Spoonbill, Spatule blanche (Platalea leucorodia). This bird was ringed in summer 2015 in The Netherlands. During the autumn migration, this spoonbill was observed in the gulf of Gabès, Tunisia. Usually, spoonbills from the Netherlands use the East Atlantic flyway and it is uncommon to observe them in Tunisia. This recovery of Dutch spoonbill is the 4th in Tunisia and the first for the gulf of Gabès (Foued HAMZA)


Species richness patterns of waterbirds wintering in the gulf of Gabès in relation to habitat and anthropogenic features

Hamza, F., Hammouda, A. & Selmi, S. (2015). Species richness patterns of waterbirds wintering in the gulf of Gabès in relation to habitat and anthropogenic features. Estuarine, Coastal and Shelf Science 165: 254-260.
doi: 10.1016/j.ecss.2015.05.025
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Identifying factors affecting waterbird diversity is a major topic in avian ecology, as well as for conservation purposes. In this work, we investigated the relevance of habitat features and human presence in predicting the diversity of waterbirds wintering in the gulf of Gabès, an important but poorly known wintering area of palearctic waterbirds. This includes two major sources of bias in macroecological studies, namely species imperfect detection and spatial non-independence among sampled communities. Our results showed that species richness overall varied among sites according to habitat quality and tidal area use by humans. In particular, large intertidal areas, characterized by high numbers of tidal channels, elevated amounts of mud and organic materials in the sediment and important coverage of seagrass, hosted a greater diversity of waterbirds with different ecological requirements than did the small and relatively homogeneous sandy beaches. Moreover, we found that intertidal area use by humans for clam harvesting was associated with high diversity of waterbirds, particularly shorebirds, suggesting positive effects of clam harvesting on shorebirds. Further investigations of habitat selection processes and foraging behaviors are however needed to more profoundly understand the role of traditional human activities in the intertidal areas of the gulf of Gabès in shaping wintering waterbird communities.

Calidris alba (Sanderling - Bécasseau sanderling): ringed in Iceland in 2011, and wintering in the Gulf of Gabès, Tunisia

Sanderling (Calidris alba). This bird was ringed in Iceland in 2011, and wintering in the gulf of Gabès, Tunisia, January 2013. (Foued Hamza / Birding in Tunisia).