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Publication number 74. Stichting WIWO

Title: Waterbirds in the Gulf of Gabès and other wetlands in Tunisia, Autumn 1999
Authors: J.F.F.P. Bos, G.M. van der Geest, N.L.M. Gilissen, R. Pahlplatz, I. Essetti & F. Ayache
Publication date: 2001

Summary

Between 18 September and 8 October 1999 an ornithological expedition of the Foundation Working Group International Waterbird and Wetland Research (WIWO) was carried out in Tunisia. Aims of the expedition were:

  • to assess the international importance of the Gulf of Gabès for waterbirds in autumn;
  • to assess the international importance of a number of coastal and inland wetlands in other parts of Tunisia for waterbirds in autumn;
  • to develop a procedure for preparing and performing integral counts of waterbirds in Kneiss;
  • to collect sight records of ringed birds and search for Slender-billed Curlews.

The largest wetland in the Gulf of Gabès is Kneiss. It is one of the most important tidal wetlands in the Mediterranean, with the biggest numbers of migrating and wintering waders in the region. We visited Kneiss from 22 to 29 September and counted approximately 77,000 waterbirds in Kneiss, including 775 grebes an herons, 1,180 Spoonbills, 3,940 Flamingos, 60,500 waders and 10,600 gulls and terns. The most numerous wader was Dunlin, totalling 27,700. The total number of waterbirds counted in Kneiss in autumn 1999 was lower than numbers counted in winter (February/March) during previous WIWO-expeditions. Wader numbers mainly account for these differences. However, this does not mean that the total number of birds using of the area in autumn is lower, because turnover in migration seasons is likely to be higher than in winter. This implies that higher proportions of populations might use Kneiss as a staging area than actually counted. The low numbers can also be explained by early passage of migrant waders before September, depending on the species and population. The 1% threshold for use in the Ramsar Convention was met for eight species, i.e. Spoonbill, Greater Flamingo, Kentish Plover, Grey Plover, Curlew Sandpiper, Dunlin, Redshank and Slender-billed Gull. Our results show that in autumn Kneiss is a wetland of major importance for waders and waterbirds.
The total number of waterbirds in the whole Gulf of Gabès was 113,277. Apart from Kneiss, 1%-tresholds were exceeded in the following areas: Golfe du Rass Rinel (Spoonbill: 1%), Intertidal zone between El Kantara and Sebkha Oum ez Zessar (Gourine) (Greater Flamingo: 1.6%; Slender-billed Gull: 1.4%), Sebkhet Sidi Garous (Lesser Crested Tern: 2.8%), Thyna Salinas (Greater Flamingo: 6.3%; Spoonbill: 2.4%).
A total of 16 wetlands outside the Gulf of Gabès were visited and waterbirds were counted. One percent thresholds were exceeded in six wetlands. The barrages at Cap Bon proved to be very important for three globally threateded duck species: Marbled Teal, Ferruginous Duck and White-headed Duck. A count of 4,250 Marbled Teals was made on one single day at Barrage Oued El Khatf and Barrage Lebna and was at the time the highest ever in Tunisia. Moreover, it was the first count showing that population estimates of both breeding and wintering numbers were too low.. The Cap Bon barrages are not only important autumn staging sites for Marbled Reals, but also the major remaining area all year round for the Tunisian population of White-headed Duck and regularly hold important concentrations of Ferruginous Duck.
A total of 21 ringed Greater Flamingo's were observed and these recoveries were submitted to the co-ordination organisations. No Slender-billed Curlews were found.

It is important that numbers and distrbution of waterbirds in Kneiss are monitored on a regular basis. However, organising and carrying out counts in large intertidal areas like Kneiss is complex. To quarantee sufficient quality of a count, ideally, a detailed plan should be available, taking into account accessibility of the area, timing of spring tide and expected locations of bird concentrations. Such a plan additionally should include counting methods, counting sections, counting routes and timetables for counters. Two scenarios to count the Kneiss area, based on experiences gained from WIWO-expeditions, are presented. The optimal scenario aims at counting as accurate as possible. A more 'pragmatic' scenario is limited by facilities and the number of participating counters.


The report contains:
  • Summary in both English and French
  • Results of waterbird counts
  • Scenarios for integral waterbird counts in Kneiss
  • Discussion on consequences for population estimates and distribution of Marbled Teals