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

Landscape-scale experiment demonstrates that Wadden Sea intertidal flats are used to capacity by molluscivore migrant shorebirds

P>1. Whether intertidal areas are used to capacity by shorebirds can best be answered by large-scale manipulation of foraging areas. The recent overexploitation of benthic resources in the western Dutch Wadden Sea offers such an 'experimental' setting. 2. We review the effects of declining food abundances on red knot Calidris canutus islandica numbers, based on a yearly large-scale benthic mapping effort, long-term colour-ringing and regular bird-counts from 1996 to 2005. We focus on the three-way relationships between suitable foraging area, the spatial predictability of food and red knot survival. 3. For each benthic sampling position, red knot intake rate (mg AFDM s-1) was predicted by a multiple prey species functional response model, based on digestive rate maximization (this model explained diet and intake rate in earlier studies on red knots). This enabled us to derive the spatial distribution of the suitable foraging area, which in each of the 10 years was analysed with a measure of autocorrelation, i.e. Moran's I. 4. Over the 10 years, when accounting for a threshold value to meet energetic demands, red knots lost 55% of their suitable foraging area. This ran parallel to a decrease in red knot numbers by 42%. Although there was also a decrease in patchiness (i.e. less information about the location of the suitable feeding sites), this did not yet lead to additional loss of birds. 5. To cope with these landscape-scale declines in food stocks, an increase in the capacity for instantaneous food processing would be required. Although we show that red knots indeed enlarged their muscular gizzards, the increase in gizzard size was not enough to compensate for the decreased feeding area. 6. Survival of islandica knots in the western Dutch Wadden Sea, based on colour-ring resightings, declined from 89% in the first half of our study period to 82% in the second half of our study period and could account for almost half of the decline in red knot numbers; the rest must have moved elsewhere in winter. 7. Densities of red knots per unit suitable foraging area remained constant at 10 knots ha-1 between 1996 and 2005, which suggests that red knots have been using the Dutch Wadden Sea to full capacity

Changes in the waterbird community of the Parc National du Banc d'Arguin, Mauritania, 1980-2017

The Parc National du Banc d’Arguin in Mauritania hosts the largest concentrations of coastal waterbirds along the East Atlantic Flyway. In spite of this importance, a review of the changes in the numbers of waterbirds in the area is lacking since the first complete count in 1980. Here we analysed the seven complete waterbird counts made since then, and the additional yearly counts made in one subunit (Iwik region) since 2003.We present evidence for changes in the community composition of waterbirds over the past four decades. Total waterbird numbers showed a decrease between 1980 and 2017, with only Great White Pelican Pelecanus onocrotalus showing a significantincrease in numbers. Five species showed significant declines: Long-tailed Cormorant Phalacrocorax africanus, Red Knot Calidris canutus, Bar-tailed Godwit Limosa lapponica, Eurasian Curlew Numenius arquata, and Western Marsh Harrier Circus aeruginosus. In the remaining species, the variation in numbers between counts was too large, and the number of complete counts too small, for trends to be detected. The yearly counts at Iwik region also showed sharp decreases in the numbers of Red Knot, Bar-tailed Godwit, and Marsh Harrier, but not of Long-tailed Cormorant and Eurasian Curlew. A multivariate analysis revealed a significant effect of year on species composition, which was caused mainly by changes in the species depending on the intertidal mudflats for feeding (generally in decline) vs. the species depending on fish and crustaceans in the sublittoral and offshore zones (often showing increases)

Fuelling conditions at staging sites can mitigate Arctic warming effects in a migratory bird

Under climate warming, migratory birds should align reproduction dates with advancing plant and arthropod phenology. To arrive on the breeding grounds earlier, migrants may speed up spring migration by curtailing the time spent en route, possibly at the cost of decreased survival rates. Based on a decades-long series of observations along an entire flyway, we show that when refuelling time is limited, variation in food abundance in the spring staging area affects fitness. Bar-tailed godwits migrating from West Africa to the Siberian Arctic reduce refuelling time at their European staging site and thus maintain a close match between breeding and tundra phenology. Annual survival probability decreases with shorter refuelling times, but correlates positively with refuelling rate, which in turn is correlated with food abundance in the staging area. This chain of effects implies that conditions in the temperate zone determine the ability of godwits to cope with climate-related changes in the Arctic

The Bijagós Archipelago:a key area for waterbirds of the East Atlantic Flyway

The Bijagós Archipelago is a group of 88 islands and islets off the coast of Guinea-Bissau in W Africa. It is a site with an undisputable ecological value, recognized nationally by the implementation of three marine protected areas, and internationally by its classification as a Biosphere Reserve and Ramsar Site. Its relatively pristine ecosystem mostly arises from local community cultural traits that have limited the overexploitation of resources until recently. Among the diverse set of habitats, its extensive mangrove forests, totalling 524 km2, cover c. 30% of the area of the archipelago, and provide crucial ecosystem services, including nursery for several fish species, safe roosting areas for waterbirds, and organic matter input to adjacent habitats. The Bijagós Archipelago also features ca. 450 km2 of intertidal flats, among the largest in the world, which sustain highly diverse benthic communities. This site holds an important part of the regional populations of several waterbird species, especially migratory shorebirds. It is the third most important site on the East Atlantic Flyway for Palearctic migratory shorebirds during their non-breeding period, and second in Africa, after the Banc d’Arguin in Mauritania. Nevertheless, very steep declines in most shorebird species are being observed in the Bijagós Archipelago, in accordance with overall declines along the flyway, and in other important sites like the Banc d’Arguin. The reasons for these declines are not fully known. Conservation, research and monitoring efforts have been increasing in the area, in an attempt to gather baseline knowledge on different aspects of relevance to waterbirds, their habitats and the ecological processes they depend upon, ultimately aiming at protecting the extraordinary biodiversity value of the Bijagós Archipelago