The waterbirds of Parc National du Banc d’Arguin: Evaluation of all complete winter counts, workshop proceedings, and a future perspective

This is the report of an initiative to evaluate the results and methodology of all shorebird counts of the Banc d’Arguin in Mauritania. This was done by means of a workshop with all participants of the 2017 count expedition and a selection of researchers in the area, and an analysis of the 2017 census in the perspective of previous censuses. The goals of this initiative were (a) to gain more knowledge on the (causes of) temporal dynamics in the shorebird numbers at Banc d’Arguin, (b) to discuss the optimal design for future shorebird monitoring of the Banc d’Arguin, and (c) to improve the collaboration between all involved parties. Total bird numbers have been declining since the first complete census in 1980 (2,384,000 birds) with 1,725,000 birds counted in the 2017 census, a slightly higher total estimate than the previous census in 2014 (1,459,000 birds). All seven total censuses combined showed a significant temporal linear trend for six species (all negative, expect for one). For all other species, the data proved insufficient to determine temporal trends on the species level. An ordination analysis of all species per section suggests that species dependent on the intertidal mudflats decline more than species depending on the sublitoral and outer sea. Trends in population growth rates confirm this pattern. Discussions during and after the workshop led to a list of recommendations for future monitoring. To determine population trends, a complete count should be undertaken more frequently, by a trained Mauritanian team. Besides more data, this will lead to more experience and a better census. This is a preferred scenario, but it will take considerable investments, particularly in the installation of a permanent, skilled and motivated team of observers. Senior bird counters, trend analysis professionals, and a local guide should be involved to train this team. A course in count data analysis should be organised the Netherlands, and frequent training sessions should be organized in Mauritania, independent of the actual counts.