The rapid destruction of habitat in biodiversity hotspots calls for the urgent formulation of conservation strategies. In this study, macro-scale biogeographical data for 33 species of Psittacines were used to select networks of priority areas, using an algorithm based on the complementarity concept. Human population size was also incorporated as a cost in the selection process, and the two networks of priority areas (with and without cost) were compared. In the comparison the number of cells selected to represent all species did not differ, but a rearrangement occurred between them. Two of the four cells were located in the same place, and the others changed location but stayed aggregated within the same regions. The study shows that it is possible to minimize human population size and represent all species in a network of priority areas.

Seabirds are one of the most threatened avian taxa and are hence a high conservation priority. Managing seabirds is challenging, requiring conservation actions at sea (e.g. Marine Protected Areas - MPAs) and on land (e.g. protection of breeding sites). Important Bird and Biodiversity Areas (IBAs) have been successfully used to identify sites of global importance for the conservation of bird populations, including breeding seabirds. The challenge of identifying suitable IBAs for tropical seabirds is exacerbated by high levels of dispersal, aseasonal and asynchronous breeding. The western Indian Ocean supports ~19 million breeding seabirds of 30 species, making it one of the most significant tropical seabird assemblages in the world. Within this is the British Indian Ocean Territory (BIOT), encompassing 55 islands of the Chagos Archipelago, which supports 18 species of breeding seabird and one of the world’s largest no-take MPAs. Between January and March in 1975 and 1996, eight and 45 islands respectively were surveyed for seabirds and the data used to designate 10 islands as IBAs. A further two were proposed following an expedition to 26 islands in February/March 2006. Due to the historic and restricted temporal and spatial nature of these surveys, the current IBA recommendations may not accurately represent the archipelago’s present seabird status and distribution. To update estimates of the BIOT breeding seabird assemblage and reassess the current IBA recommendations, we used seabird census data collected in every month except September from every island, gathered during 2008–2018. The maximum number of breeding seabirds for a nominal year was 281,596 pairs of 18 species, with three species making up 96%: Sooty Tern Onychoprion fuscatus - 70%, Lesser Noddy Anous tenuirostris - 18% and Red-footed Booby Sula sula - 8%. Phenology was a complex species-specific mix of synchronous and asynchronous breeding, as well as seasonal and aseasonal breeding. Nine of the 10 designated IBAs and the two proposed IBAs qualified for IBA status based on breeding seabirds. However, not every IBA qualified each year because Sooty Terns periodically abandoned breeding islands and Tropical Shearwater Puffinus bailloni breeding numbers dropped below IBA qualifying criteria in some years. Further, one survey per year does not always capture the periodic breeding of some tropical seabirds. We propose therefore, that IBAs in BIOT are better designated at the island cluster level rather than by specific island and require two surveys six months apart per year. This work highlights the merits of long-term, systematic, versus incidental surveys for breeding tropical seabirds and the subsequent associated designation of IBAs.

Seabirds face a diverse array of threats and are considered to comprise one of the most threatened avian groups globally. Development of appropriate conservation action requires a knowledge of the marine distribution of seabirds, furnished either by tracking the movements of individuals, or from at-sea surveys. Obtaining information on the distribution of the smallest seabird species, the storm-petrels Hydrobatidae, is challenging, but the recent development of <1 g GPS tracking tags now enables high-precision tracking and this study reports the first multi-year high-precision tracking of European Storm-petrels Hydrobates pelagicus from their largest UK breeding colony. A total of 42 successful tag deployments were made over four breeding seasons during incubation, brooding and post-brood phases, and there was no evidence of adverse impacts on adult body mass or nest survival rates. Foraging trips lasted between one and three days and ranged up to 397 km from the colony (median = 159 km). Foraging range and total distance covered were positively correlated with trip duration but did not differ across breeding stages. Storm-petrels did not feed to the west of the colony at the edge of the continental shelf where high concentrations have been reported in previous decades from boat surveys, but rather, foraging was restricted to shallow waters south of the colony, consistent across individuals, breeding stages and years. Two areas were identified that exceed the threshold criteria for marine Important Bird Area status and should be considered for statutory protection. The home range estimated across all three breeding stages overlapped with 206 active hydrocarbon wells and 14 operating platforms which represent potential threats as sources of surface pollution or through attraction of birds to gas flares. Improved understanding of the foraging distribution of storm-petrels from this protected colony greatly assists the identification of potential threats and informs appropriate marine spatial planning.

Over 1,200 Important Bird Areas (IBAs) have been identified in Africa, each meeting at least one of four objective criteria that identify it as an area of high conservation importance for birds. Despite their biodiversity value, many IBAs are threatened by habitat degradation and a high proportion lack legal protection. We integrate an inventory of these IBAs with remote sensing data to identify patterns that could be used to assess priorities for monitoring and conservation. Land cover composition in IBAs differed significantly from that in buffer zones of the same area immediately surrounding them and was significantly more homogeneous. Agriculture and deforestation were the most prevalent threats to IBAs, particularly in IBAs containing a high proportion of dense forest or shrub. Human population density within IBAs was no lower than that immediately outside IBAs, and was around three times higher than the average for sub-Saharan Africa. However, projected human population growth was lower than the average for sub-Saharan Africa, with the projected increase greatest in IBAs with a high proportional cover of dense forest and mosaic woodland and lowest in IBAs with a higher grassland component. Fifty seven percent of IBAs fell within or overlapped Protected Areas, though this percentage differed between different categories of IBA. IBAs that were included within Protected Areas supported a greater number of globally threatened bird species and contained proportionally more dense forest, woodland and shrub than IBAs falling outside Protected Areas. IBAs outside Protected Areas contained a high proportion of mosaic woodland and open water, suggesting that such habitats are under-protected in Africa. We suggest that because the most prevalent threats to IBAs involve changes in land cover that could be detected from satellites, remote sensing could play an important role in the monitoring of African IBAs. This would permit monitoring of a wider range of sites than is possible solely by conventional, ground-based approaches.

Realistic population size estimates for waterbirds are crucial for the application of wetland conservation strategies, since the identification of internationally important wetlands is based on local numbers relative to the population size of the respective species. Central Asia is a poorly surveyed region that is situated at the intersection of migration routes that lead waterbirds from Western Siberia to the south-west (South-West Asia, East Africa) and to the south-east (South Asia, India). We calculated waterbird population estimates for the Tengiz–Korgalzhyn region, a large wetland complex in the steppe zone of Central Kazakhstan, based on waterbird surveys conducted between 1999 and 2004. For 20 of 43 species analysed the region supported more than 5% of the relevant flyway populations. Five species occurred with more than 40% of the flyway totals, including the Endangered White-headed Duck Oxyura leucocephala and the Vulnerable Dalmatian Pelican Pelecanus crispus. Peak numbers were recorded in summer and autumn and for most species numbers were more than an order of magnitude lower on spring migration compared with autumn migration. We identified 72 individual sites that held more than 20,000 waterbirds or more than 1% of a particular flyway population at least once. These sites are likely to constitute priorities for conservation. The general conservation status of the region is favourable, since many of the important sites are located within a strict nature reserve. However, outside the reserve hunting, fishing and powerline casualties represent conservation issues that should be monitored more carefully in the future.

Seabird populations breeding in the UK Overseas Territories remain relatively understudied compared to UK seabird populations, despite their international importance. Here we present results from one of the first seabird tracking studies in the Caribbean region, of Brown Boobies Sula leucogaster breeding on the Important Bird Area (IBA) of Dog Island, Anguilla. Birds were tracked for 5–7 days during the chick-rearing period using GPS data loggers. We assess how representative the at-sea areas of use (utilisation distributions) identified from our sample of 16 birds are likely to be of those of the whole breeding colony, and examined the effect that grid cell size used in the ‘time-in-area’ analytical approach has on these predictions. We also assess the effectiveness of the BirdLife International’s seaward extension approach to marine IBA designation, where terrestrial IBAs are buffered a set distance using existing information on the foraging radii of the same or similar breeding species. Foraging trips were 125.3 ± 54.4 (SD) km long and lasted for 5.6 ± 1.95 hrs on average. Birds travelled into the waters of four neighbouring territories; Saint Martin, Saba, Saint Eustatius and Saint Barthelemy. Our models suggest that many more individuals would need to be tracked to fully identify important at-sea areas for this colony, although this depends on the scale that important areas are defined. Whilst a smaller grid cell size may be necessary for assessing fine-scale habitat use, a larger grid cell size may be more appropriate for marine spatial planning processes. Although the BirdLife Seaward extension approach using maximum foraging distance recorded from Brown Boobies at a Mexican colony predicted a smaller foraging area than that used by Dog Island birds this approach still incorporated at least 99% of their 50% UD, 98% of their 75% UD and 86% of the 95% UD.

The Philippine islands hold a concentration of species diversity and endemism of global importance, yet few studies have analyzed biogeographic patterns or attempted to prioritize areas for conservation within the archipelago. We analyzed distributions of 386 species on 28 Philippine islands and island groups, documenting intense concentration of species richness, especially of endemic species, on the two largest islands, Mindanao and Luzon. Factors identified as influencing species richness included island area, maximum elevation, and Pleistocene patterns of connection and isolation. Reserve systems were developed based on heuristic complementarity algorithms, and compared with the existing Integrated Protected Areas (IPAS) system in the country, showing that IPAS is an impressive first step towards protecting avian diversity in the country. Addition of presently proposed reserves on Palawan and Mindoro would make IPAS a near-optimal reserve design, at least at the level of island representation. Important challenges remain, however, with regard to design of reserve systems within islands to represent complete island avifaunas.

China makes a unique and vital contribution to maintaining global and regional waterbird diversity and conservation. Despite considerable historical conservation efforts, the continued loss of waterbird diversity and abundance necessitates a contemporary review of Chinese sites of conservation significance. The Ecological Protection Red Line (EPRL) was proposed by China’s Central Government in 2013 to protect areas providing crucial ecosystem services and provides the opportunity for such a review to enhance waterbird conservation in China. By incorporating various sources of data, surveys and information, we identified a suite of sites of waterbird conservation significance in China, following the Ramsar Site Criteria/Important Bird and Biodiversity Area (IBA) Criteria. In total, we identified 422 sites, of which the existing 286 IBA sites formed the basis of the site safeguard network. Altogether, these sites of waterbird conservation significance constitute over 727,000 km2 (7.6% of China’s land surface). Over half of the area of these sites is outside China’s national nature reserves, thus confirming the importance and urgency of including them in the EPRL for the effective conservation of waterbird sites. We suggest that this assessment of sites of waterbird importance offers a useful model to apply to other taxa, such as terrestrial birds and mammals.

Important Bird and Biodiversity Areas (IBAs) are sites identified as being globally important for the conservation of bird populations on the basis of an internationally agreed set of criteria. We present the first review of the development and spread of the IBA concept since it was launched by BirdLife International (then ICBP) in 1979 and examine some of the characteristics of the resulting inventory. Over 13,000 global and regional IBAs have so far been identified and documented in terrestrial, freshwater and marine ecosystems in almost all of the world’s countries and territories, making this the largest global network of sites of significance for biodiversity. IBAs have been identified using standardised, data-driven criteria that have been developed and applied at global and regional levels. These criteria capture multiple dimensions of a site’s significance for avian biodiversity and relate to populations of globally threatened species (68.6% of the 10,746 IBAs that meet global criteria), restricted-range species (25.4%), biome-restricted species (27.5%) and congregatory species (50.3%); many global IBAs (52.7%) trigger two or more of these criteria. IBAs range in size from < 1 km2 to over 300,000 km2 and have an approximately log-normal size distribution (median = 125.0 km2, mean = 1,202.6 km2). They cover approximately 6.7% of the terrestrial, 1.6% of the marine and 3.1% of the total surface area of the Earth. The launch in 2016 of the KBA Global Standard, which aims to identify, document and conserve sites that contribute to the global persistence of wider biodiversity, and whose criteria for site identification build on those developed for IBAs, is a logical evolution of the IBA concept. The role of IBAs in conservation planning, policy and practice is reviewed elsewhere. Future technical priorities for the IBA initiative include completion of the global inventory, particularly in the marine environment, keeping the dataset up to date, and improving the systematic monitoring of these sites.

Population size estimates of waders, gulls and terns passing through or breeding in Central Asia are very scarce, although highly important for global flyway population estimates as well as for targeting local conservation efforts. The Tengiz-Korgalzhyn region is one of the largest wetland complexes in Central Asia. We conducted surveys in this region between 1999 and 2008 and present estimates of population size as well as information on phenology and age structure for 50 species of Charadriiformes. The Tengiz-Korgalzhyn wetlands are especially important for Red-necked Phalaropes Phalaropus lobatus and Ruffs Philomachus pugnax with, respectively, 41% and 13% of their flyway populations using the area during spring migration. The region is also an important post-breeding moulting site for Pied Avocets Recurvirostra avosetta and Black-tailed Godwits Limosa limosa used by, respectively, 5% and 4% of their flyway populations. Besides its key importance as a migratory stopover site, the study area is a key breeding site for the Critically Endangered Sociable Lapwing Vanellus gregarius, the Near Threatened Black-winged Pratincole Glareola nordmanni and for Pallas’s Gull Larus ichthyaetus with 16%, 6% and 5% of their world populations, respectively. We identified 29 individual sites that held more than 1% of the relevant flyway populations of at least one species of Charadriiformes. Including data on other species of waterbirds (mainly waterfowl), there were 93 sites that qualify for Important Bird Areas (IBA). About half of them are protected in a state nature reserve, while an additional 20% are recognised as IBAs. Nevertheless, 28 important sites are currently not recognised as IBAs nor are they protected by other conservation means. These sites require conservation attention.

Vulture populations are in severe decline across Africa and prioritization of geographic areas for their conservation is urgently needed. To do so, we compiled three independent datasets on vulture occurrence from road-surveys, GPS-tracking, and citizen science (eBird), and used maximum entropy to build ensemble species distribution models (SDMs). We then identified spatial vulture conservation priorities in Ethiopia, a stronghold for vultures in Africa, while accounting for uncertainty in our predictions. We were able to build robust distribution models for five vulture species across the entirety of Ethiopia, including three Critically Endangered, one Endangered, and one Near Threatened species. We show that priorities occur in the highlands of Ethiopia, which provide particularly important habitat for Bearded Gypaetus barbatus, Hooded Necrosyrtes monachus, Rüppell’s Gyps rüppelli and White-backed Gyps africanus Vultures, as well as the lowlands of north-eastern Ethiopia, which are particularly valuable for the Egyptian Vulture Neophron percnopterus. One-third of the core distribution of the Egyptian Vulture was protected, followed by the White-backed Vulture at one-sixth, and all other species at one-tenth. Overall, only about one-fifth of vulture priority areas were protected. Given that there is limited protection of priority areas and that vultures range widely, we argue that measures of broad spatial and legislative scope will be necessary to address drivers of vulture declines, including poisoning, energy infrastructure, and climate change, while considering the local social context and aiding sustainable development.

We developed distributional models for 90 threatened bird species in China, and used heuristic complementarity algorithms to prioritize areas for conservation. The pixel-based area selection prioritized 20 areas for protection, which covered all species analysed. Area selecting for endangered species based on the existing biosphere reserve system included only 37-62 species in eleven reserves, leaving 28-53 species unprotected. We employed algorithms for area selection based on species richness and rarity and obtained two views of a most efficient reserve network. We used the distributional hypotheses to identify additions to the reserve system that would improve its effectiveness substantially. The pixel-based area selection approach includes species much more efficiently on a per-area basis, and thus offers exciting perspectives for improved protection of the country's endangered avifauna.

BirdLife International´s Important Bird and Biodiversity Areas (IBA) Programme has identified, documented and mapped over 13,000 sites of international importance for birds. IBAs have been influential with governments, multilateral agreements, businesses and others in: (1) informing governments’ efforts to expand protected area networks (in particular to meet their commitments through the Convention on Biological Diversity); (2) supporting the identification of Ecologically or Biologically Significant Areas (EBSAs) in the marine realm, (3) identifying Wetlands of International Importance under the Ramsar Convention; (4) identifying sites of importance for species under the Convention on Migratory Species and its sister agreements; (5) identifying Special Protected Areas under the EU Birds Directive; (6) applying the environmental safeguards of international finance institutions such as the International Finance Corporation; (7) supporting the private sector to manage environmental risk in its operations; and (8) helping donor organisations like the Critical Ecosystems Partnership Fund (CEPF) to prioritise investment in site-based conservation. The identification of IBAs (and IBAs in Danger: the most threatened of these) has also triggered conservation and management actions at site level, most notably by civil society organisations and local conservation groups. IBA data have therefore been widely used by stakeholders at different levels to help conserve a network of sites essential to maintaining the populations and habitats of birds as well as other biodiversity. The experience of IBA identification and conservation is shaping the design and implementation of the recently launched Key Biodiversity Areas (KBA) Partnership and programme, as IBAs form a core part of the KBA network.

Important Bird Areas (IBAs) form a network of priority sites that are critical for the conservation of birds and biodiversity. A standard framework for monitoring IBAs is being implemented by the BirdLife Partnership globally. Scores are assigned on a simple ranked scale for state (condition), pressure (threats) and response (conservation action) at each site, from which IBA indices can be calculated. In Kenya, this scoring system was applied retrospectively using information in the national IBA directory (1999) and subsequent status reports (2004 and 2005). IBA indices for 36 IBAs show that their average condition deteriorated between 1999 and 2005, with the mean state score being between ‘unfavourable’ and ‘near favourable’. Pressures on IBAs showed a slight decline in intensity, especially from 2004 to 2005, coincident with an improvement in management that was reflected in increasing response scores. Compared to unprotected IBAs, officially protected sites had substantially greater conservation responses underway, were subject to marginally lower pressures and tended to be in slightly better condition. Other disaggregations of the data allow comparisons to be made for sites in different habitats, of different size, and managed by different agencies. This national example for Kenya suggests that the BirdLife IBA monitoring framework provides a simple but effective way of tracking trends in the state of IBAs, the pressures upon them, and the responses in place. The system is sensitive enough to detect differences between sites and over time, but simple enough to be implemented with little training and without sophisticated technology. The results provide vital information for managers of individual protected areas, management agencies responsible for suites of sites, and national governments, and can be used to track progress in tackling the global biodiversity crisis.

The mountains of south-eastern Nigeria are a western extension of the Cameroon mountain range, which is classified as an endemic bird area (EBA). Unlike its eastern extension in Cameroon, most of the ornithological surveys in the western extension of the Cameroon highlands in Nigeria have produced only limited checklists and inventories. There is a clear need for quantitative baseline data so that conservation problems can be identified. Twenty line transects covering a total transect length of 28.8 km were used to survey five sites (Afi Mountain Wildlife Sanctuary, Oban Division and Okwangwo Division of Cross River National Park, Sankwala Mountains and Mbe Mountains) in the westernmost extension of the Cameroon Mountains EBA in south-eastern Nigeria. Vegetation measurements were taken to control for the potential confounding effect of variation in vegetation density and structure on detectability of birds between sites. The 193 bird species recorded in Afi, 158 in Sankwala, 124 in Oban, 100 in Mbe and 73 in Okwangwo Division included most of the Cameroon highlands restricted range species. The results show that the mountains of south-eastern Nigeria are important parts of the Cameroon EBA, particularly Afi Mountain Wildlife Sanctuary. However these sites are threatened by fire and livestock grazing on the hilltops, shifting agriculture on the hillsides and lowlands, and logging for timber in some parts, as well as wildlife hunting for bushmeat.

We present an assessment of the Southern Paraguayan Grasslands using Important Bird Areas (IBAs) located in a grassland landscape mosaic. Eleven IBAs in southern Paraguay were evaluated 10 years after their designation, using the BirdLife International method to assess the state, pressure, and response of these areas, during 2017 and 2018. Overall, the Pressure from ecosystem modifications led by fire, and fire suppression, agricultural expansion, and intensification due to farming and grazing have been identified as the major threats to IBAs. Regarding the State, 64% of the IBAs presented Very poor habitat quality to support grassland bird communities. The level of conservation Response was mostly negligible when considering conservation designation, management planning and conservation actions for the trigger species. Our results provide useful information to partners to reconsider these areas as IBAs as most of them no longer fulfill international requirements, we also highlight the importance of strengthening national policies to adequately protect natural grasslands.

Many migratory waterbird populations are in decline and loss of natural wetlands is one of the main causes. However, some species may respond positively to artificial wetland recreation. In Extremadura (south-west Europe), several large reservoirs were created for irrigation since the 1960s and some comparatively small reservoirs were built from the late 1990s onwards close to rice fields. Here we analyse the abundance of wintering dabbling ducks (Anas spp.) in Extremadura before (1991–1994) and after (2007–2010) the creation of these new reservoirs in order to address the current importance of the area for this guild within the East Atlantic Flyway (EAF). A mean of 25,277 dabbling ducks wintered in the study area during 1991–1994, increasing to 46,163 individuals during 2007–2010. After controlling for environmental variables, Northern Pintail Anas acuta, Common Teal A. crecca and Northern Shoveler A. clypeata experienced significant increases in the area between both periods, and only Eurasian Wigeon A. penelope suffered a significant decrease. Mallard A. platyrhynchos and Gadwall A. strepera populations did not show any significant trend. The large older reservoirs experienced overall population decreases between the two periods, with four new reservoirs holding more than 35,000 wintering dabbling ducks. Our results reflect an overall improvement in habitat conditions, driven by the creation of reservoirs near to rice fields that could have resulted in a partial redistribution of wintering dabbling ducks in the EAF. The area emerges as one of the most important wintering sites for dabbling ducks in southern Europe, regularly exceeding two of the Ramsar Convention criteria for the conservation of several populations. The protection of these new reservoirs by legal mechanisms would guarantee the existence of a large functional wetland area, which could also mitigate the loss of natural wetlands for populations using the EAF.

The Japanese Murrelet Synthliboramphus wumizusume is a rare, globally ‘Vulnerable’ seabird, endemic to Japan and South Korea. However, little is known of its at-sea distribution, habitat or threats. We conducted several years of at-sea surveys around Japan to model Japanese Murrelet density in relation to habitat parameters, and make spatial predictions to assess the adequacy of the current Japanese marine Important Bird and Biodiversity Area (IBA) network for the species. During a five-year period, 3,485 km of at-sea surveys recorded 3,161 Japanese Murrelets around four breeding locations. Maximum murrelet group size was 90 individuals with a mean group size of 2.9 ± 4.2 individuals. Models of Japanese Murrelet at-sea density around the two largest breeding locations predicted that almost all murrelets occur within 30 km of the breeding colony and most within 10 km. Murrelets were predicted closer to the colony in May than in April and closer to the colony at a neritic colony than at an offshore island colony. Additionally, murrelets breeding on an offshore island colony also commuted to mainland neritic habitat for foraging. The marine habitat used by Japanese Murrelets differed between each of the four surveyed colonies, however oceanographic variables offered little explanatory power in models. Models with colony, month and year generated four foraging radii (9–39 km wide) containing murrelet densities of > 0.5 birds/km2. Using these radii the Japanese marine IBA network was found to capture between 95% and 25% of Japanese Murrelet at-sea habitat while breeding and appears appropriately configured to protect near-colony murrelet distributions. Given the range of marine habitats that breeding murrelets inhabit, our simple models offer an applicable method for predicting to unsampled colonies and generating ecologically-informed seaward extension radii. However, data on colony populations and further at-sea surveys are necessary to refine models and improve predictions.

Networks of protected areas (PAs) where human activities are allowed at different degrees are fundamental to ensure the long-term conservation of biological diversity and ecological processes. However, studies aimed at assessing their effectiveness, focusing on several species simultaneously are scarce. We assessed the effectiveness of the system of protected areas (PAs) of Lombardy, Northern Italy, in conserving bird populations by comparing the changes from 1992 to 2013 in the occurrence of 54 breeding bird species censused in areas classified in different protection categories, namely Nature Reserves (NRs), areas designed predominantly for the protection of nature; Regional Parks (RPs), naturally valuable areas where human activities, including intensive agriculture, are allowed; and non-protected areas (NPAs). Overall, occurrence of common birds increased in Lombardy in the last 20 years and farmland and long-distance migrants (LDMs), which suffered sharp declines at a continental scale, showed stable and increasing trends, respectively. These trends were, however, the balance between those of species whose occurrence markedly increased, and those of species that dramatically declined. Species occurred more often in PAs than in NPAs, while temporal trends in occurrence were significantly more positive in RPs than in both NRs and NPAs. Hence, PAs seemed effective in preserving common bird communities. Occurrence of woodland and short-distance migrant species was higher in PAs than in NPAs, while occurrence of farmland species and LDMs was similar in all protection categories. PAs of Lombardy appear therefore effective only in protecting some categories of birds. Farmland and LDM birds would benefit more from ecologically sustainable land-use policies aiming at improving agro-ecosystem biodiversity than from protected areas.

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 significant increase 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 change in species composition over time, 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).