Climate change presents a particularly complex challenge in the context of flyway scale conservation of migratory bird species as it requires coordinated action by multiple countries along these species’ migratory routes. Coordinating conservation responses requires understanding the vulnerability of species and their habitats to climate change at the flyway scale throughout each species’ annual cycle. To contribute to such understanding, we used species distribution models to assess the exposure to climate change of waterbird species that are the focus of the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA). We found that the species with the smallest proportion of their current range projected to be climatically suitable by 2050 (those whose distributions respond to changes in water availability but that do not perform synchronised migration) are dispersive species in the Afrotropical biogeographic realm, and migratory species in their breeding season, particularly Arctic breeding waders. These species also have the most limited availability of newly suitable areas. Projections for most other Palearctic migratory waterbird species suggest that losses of suitable areas in their current passage and wintering ranges may be largely offset by new areas becoming climatically suitable. The majority of migratory Palearctic waterbirds in the breeding season and Afrotropical waterbirds are widely dispersed with only a small proportion of their populations currently supported by ‘Critical Sites’ (i.e. sites that are either important for Globally Threatened Species or support 1% of the bioregional population of any waterbird species). This makes it unlikely that climate change adaptation measures focusing only on key sites will be sufficient to counter the predicted range losses. Therefore, climate change adaptation responses should also be implemented at the landscape scale for Afrotropical waterbirds and for breeding populations of Palearctic migrant waterbirds.

Nearly 300 species of landbirds, whose populations total billions, migrate between the Neotropics and North America. Many migratory populations are in steep decline, and migration is often identified as the greatest source of annual mortality. Identifying birds’ needs on migration is therefore central to designing conservation actions for Nearctic-Neotropical migratory birds; yet migration through the Neotropics is a significant knowledge gap in our understanding of the full annual cycle. Here, we synthesise current knowledge of Neotropical stopover regions and migratory bottlenecks, focusing on long-distance, migratory landbirds that spend the boreal winter in South America. We make the important distinction between “true” stopover—involving multi-day refuelling stops—and rest-roost stops lasting < 24 hours, citing a growing number of studies that show individual landbirds making long stopovers in just a few strategic areas, to accumulate large energy reserves for long-distance flights. Based on an exhaustive literature search, we found few published stopover studies from the Neotropics, but combined with recent tracking studies, they describe prolonged stopovers for multiple species in the Orinoco grasslands (Llanos), the Sierra Nevada de Santa Marta (Colombia), and the Yucatan Peninsula. Bottlenecks for diurnal migrants are well described, with the narrowing Central American geography concentrating millions of migrating raptors at several points in SE Mexico, Costa Rica, Panama and the Darién. However, diurnally migrating aerial insectivores remain understudied, and determining stopover/roost sites for this steeply declining group is a priority. Despite advances in our knowledge of migration in the Neotropics, we conclude that major knowledge gaps persist. To identify stopover sites and habitats and the threats they face, we propose a targeted and collaborative research agenda at an expanded network of Neotropical sites, within the context of regional conservation planning strategies.

The East Asian-Australasian Flyway supports the greatest diversity and populations of migratory birds globally, as well as the highest number of threatened migratory species of any flyway, including passerines (15 species). However it is also one of the most poorly understood migration systems, and little is known about the populations and ecology of the passerine migrants that breed, stop over and winter in the habitats along this flyway. We provide the first flyway-wide review of diversity, ecology, and conservation issues relating to 170 species of long-distance and over 80 short-distance migrants from 32 families. Recent studies of songbird migration movements and ecology is limited, and is skewed towards East Asia, particularly Mainland China, Taiwan, Russia, Japan and South Korea. Strong evidence of declines exists for some species, e.g. Yellow-breasted Bunting Emberiza aureola, but tends to be fragmentary, localised or anecdotal for many others. More species have small breeding ranges (< 250,000 km2) and/or are dependent on tropical forests as wintering habitat than those in any other Eurasian migratory system, and are thus more vulnerable to habitat loss and degradation throughout their ranges. Poorly regulated hunting for food and the pet trade, invasive species and collisions with man-made structures further threaten migratory songbirds at a number of stop-over or wintering sites, while climate change and habitat loss may be of increasing concern in the breeding ranges. A key conservation priority is to carry out intensive field surveys across the region while simultaneously tapping into citizen science datasets, to identify important stop-over and wintering sites, particularly for poorly-known or globally threatened species across South-East Asia and southern China for targeted conservation actions. Additionally, the advent of miniaturised tracking technology, molecular and isotopic techniques can provide novel insights into migration connectivity, paths and ecology for species in this migration system, complementing data from banding exercises and observation-based surveys, and could prove useful in informing conservation priorities. However, until most states along the East Asian-Australasian flyway ratify the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and other cross-boundary treaties, the relative lack of cross-boundary cooperation, coordination and information sharing in the region will continue to present a stumbling block for effective conservation of migratory passerines.

The Numeniini is a tribe of 13 wader species (Scolopacidae, Charadriiformes) of which seven are Near Threatened or globally threatened, including two Critically Endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian- Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species.

Rice fields provide functional wetlands for declining shorebirds and other waterbirds around the world, but fundamental aspects of their stopover ecology in rice fields remain unknown. We estimated the length of stay of Black-tailed Godwits Limosa limosa migrating through rice fields, and showed the international importance of Extremadura’s rice fields (south-west Spain) for this Near Threatened shorebird species. Overall, large numbers of Black-tailed Godwits en route to their breeding grounds had long lengths of stay in the rice fields (34.7 ± 1.7, 14.4 ± 2.0 and 8.3 ± 1.2 days in godwits radio-tagged in late January, early February, and late February, respectively). The long lengths of stay of godwits in rice fields, together with some aspects of their feeding ecology, suggest that rice fields are suitable staging habitats, and therefore they could play an important role as buffer habitats against the loss or degradation of natural wetlands. Extremadura’s rice fields supported at least 14% of the declining Western European population of Black-tailed Godwit, and its increasing number in south-west Spain probably reflects a population shift towards the northern part of the winter range. We strongly suggest the inclusion of Extremadura’s rice fields as a Special Protection Area for birds under the European Union Directive on the conservation of wild birds.

An estimated 19% of the world's 9,856 extant bird species are migratory, including some 1,600 species of land- and waterbirds. In 2008, 11% of migratory land- and waterbirds were classed by BirdLife International as threatened or near-threatened on the IUCN Red List. Red List indices show that these migrants have become more threatened since 1988, with 33 species deteriorating and just six improving in status. There is also increasing evidence of regional declines. Population trend data show that more Nearctic–Neotropical migrants have declined than increased in North America since the 1980s, and more Palearctic–Afrotropical migrants breeding in Europe declined than increased during 1970–2000. Reviews of the status of migratory raptors show unfavourable conservation status for 51% of species in the African–Eurasian region (in 2005), and 33% of species in Central, South and East Asia (in 2007). Land-use change owing to agriculture is the most frequently cited threat affecting nearly 80% of all threatened and near-threatened species. However, while agricultural intensification on the breeding grounds is often proposed as the major driver of declines in Palearctic–Afrotropical migrants, some species appear to be limited by the quantity and quality of available habitat in non-breeding areas, notably the drylands of tropical Africa. Forest fragmentation in breeding areas has contributed to the declines of Nearctic–Neotropical migrants with deforestation in non-breeding areas another possible factor. Infrastructure development including wind turbines, cables, towers and masts can also be a threat. Over-harvesting and persecution remain serious threats, particularly at key migration locations. Climate change is affecting birds already, is expected to exacerbate all these pressures, and may also increase competition between migratory and non-migratory species. The conservation of migratory birds thus requires a multitude of approaches. Many migratory birds require effective management of their critical sites, and Important Bird Areas (IBAs) provide an important foundation for such action; however to function effectively in conserving migratory species, IBAs need to be protected and the coherence of the network requires regular review. Since many migratory species (c. 55%) are widely dispersed across their breeding or non-breeding ranges, it is essential to address the human-induced changes at the wider landscape scale, a very considerable challenge. Efforts to conserve migratory birds in one part of the range are less effective if unaddressed threats are reducing these species' populations and habitats elsewhere. International collaboration and coordinated action along migration flyways as a whole are thus key elements in any strategy for the conservation of migratory birds.

Austral migrants are species that breed in temperate areas of South America and migrate north, towards or into Amazonia, for the southern winter. Migrations among these species are the most extensive of Southern Hemisphere migrations, and the austral system represents a third major migration system, in the sense that the term has been applied to Northern Hemisphere temperate-tropical migration. The geography of South America greatly influences the austral system. Lack of east-west geographical barriers and the shape of the continent promote a pattern of partially overlapping breeding and wintering ranges. The suboscine family Tyrannidae, the tyrant-flycatchers, is the largest group of austral migrants, with other major families including Emberizidae, Anatidae, Furnariidae, Accipitridae and Hirundinidae. Tyrant-flycatchers constitute more than one-half of the passerine austral migrants and roughly one-third of total austral migrants, a taxonomic domination seen in no other global migration system. Parallels exist, however, between austral migration and the Nearctic and Palearctic systems. Many of the same families, including Hirundinidae, Anatidae and Charadriidae, exhibit similarly high degrees of migratory behavi-our in each system. Passerine migration in the austral system is similar in numbers to that of the Nearctic-Neotropical system, but species migrate shorter distances and breed in more open and scrubby habitats. Possible differences in year-round resource availability between South American and North American temperate forests, in addition to differing availability of these habitats, may contribute to the low numbers of forest-dwelling austral migrants.

We present the first study of the spatial and temporal dynamics of raptors and large soaring birds from the Isthmus of Tehuantepec, Mexico. Using systematic migration counts from multiple localities in the southern states of Oaxaca and Chiapas, as well as observations of their flight trajectories during eight consecutive years (2007–2014), we describe the magnitude of these movements, their geographic extent, and the phenology of the most abundant species in both spring and fall seasons. The most abundant species were Turkey Vulture Cathartes aura, Swainson’s Hawk Buteo swainsoni, Broad-winged Hawk Buteo platypterus, Wood Stork Mycteria americana, American White Pelican Pelecanus erythrothynchos, Franklin’s Gull Leucophaeus pipixcan, and American Kestrel Falco sparverius. In spring, the seasonal average magnitude of migration was over 28,000 birds, while in autumn the average was over one million. The aggregated seasonal phenologies recorded illustrate a variety of migration patterns. The inter-annual variation is lower in autumn than in spring. Migrating raptors and other soaring birds did not seem to use any topographical feature as a leading line for their movements in spring, while in autumn they did. We estimated the main axis of spring flights to run along a SE–NW vector, while autumn migration follows a WNW–ESE general trajectory. Our results place the isthmus as one of the five most important sites in the world for raptors and soaring migrants. Sustaining annual migration counts at these sites is of high importance to track substantial portions (> 90%) of the global population of Turkey Vulture and Swainson’s Hawk, as well as over 10% of the global population of Broad-winged Hawk. Autumn migration counts have the potential for long-term population monitoring.

Stable isotopes (δD, δ13C, δ15N) were measured in adult and juvenile Amur Falcon Falco amurensis feathers to understand the migratory connectivity of this species. Using the OIPC (Online Isotopes in Precipitation Calculator) and a calibration curve for American Kestrels Falco sparverius we predicted the breeding range of South African Amur Falcons in the Palaearctic. δD values for juvenile feathers (mean ± SE = -58.1 ± 2.5‰, range -83.9 to -25.7‰) and predicted Palaearctic annual precipitation values indicated that juvenile Amur Falcons in South Africa originated from across their entire Palaearctic range. This rejects the leapfrog migration hypothesis and suggests the widespread movement of birds south, with a funnelling effect into the subregion where they become concentrated over a narrower distribution range. Adult δDf values were more depleted (-37.4 ± 1.8‰, range = -71.3 to -9.3‰) than predicted annual precipitation values for sites where feathers moulted in South Africa (-20.2 ± 0.9‰) but there was no correlation between δDp and δDf. This, together with significant variation of δ13C among sites and annual fluctuations in roost sizes, suggests that roost site fidelity is low in the overwintering range. Populations not confined to breeding sites in South Africa are able to move widely across the subregion, feeding on a broad range of arthropods that become seasonally abundant during the austral summer. Total population estimates for South Africa are significantly lower than global estimates so a significant proportion of the population may not overwinter in South Africa or global populations are significantly lower than estimated. In South Africa, roosts that number hundreds to thousands of individuals are often in large exotic trees, e.g. Eucalyptus sp. They are often tolerant of disturbance at roosts which may be of little concern for their conservation. Habitat changes in the overwintering range in South Africa though, particularly due to agriculture, afforestation and strip mining, may affect global population numbers. There is also concern over the persecution of birds along their migratory route.

The southern portion of South America plays an important role for the conservation of many waterfowl and waders. Migratory movements were, till recently, known only for Arctic or Patagonian species. The only exception was the Southern Pochard Netta peposaca, with a west—east winter migration from the lower Parana River valley to south Brazil coastal wetlands. The banding studies that have been conducted by the Centro de Pesquisas para a Conservação das Aves Silvestres (CEMAVE/IBAMA) since 1980, directly or through agreements with local organizations, showed more details of this migration, plus indications that other aquatic species such as Chilean Flamingo Phoenicopterus chilensis, other duck species, Neotropic Cormorant Phalacrocorax olivaceus and White-faced Plegadis chihi may follow the same pattern. A migration into the same area the Pantanal population of the Wood Stork Mycteria americana was only recently discovered, and other species may also do likewise when the Pantanal is seasonally flooded. The studies of such bird migration or movements between the main South American wetlands are of great importance to understanding their conservation needs, especially when international cooperation among the countries plays a most important role. The region has been suffering human pressures of various types, from land reclamation for pasture and/or agriculture to the operation, in the last 30 years, of big hydroelectric dams which affect the natural flow of rivers or keep flood-plains under water. The impending construction of the Hidrovia Paranà/Paraguay, a large project for heavy river use as a main transportation route, may represent an enormous impact on such rich aquatic habitats, demanding immediate cooperation among the countries involved to mitigate negative effects on the environment. The impact may be similar to what happened in the Mississippi valley early this century. The west-east movements between the Paranà River valley and south Brazil are of special conservation interest, as a nationally threatened species (in Brazil) is involved (the Chilean Flamingo) as well as duck species targeted for the hunting season in the area.

Mapping migratory routes and the distribution of species during migration requires information collected over large scales (e.g. survey data), or the ability to follow specific movements (e.g. using tracking devices), which is often limited to a few individuals. For endangered species, such techniques may be impractical, but developments in flight range modelling allow inferences about migratory routes and potential site occupancy, given a few morphological parameters. We modelled flight range in a rapidly declining population of continental Black-tailed Godwits Limosa limosa limosa departing from a staging site in Iberia during spring migration and found that the vast majority of godwits are able to reach the breeding grounds in a single flight. Contrary to the traditional use of staging sites in France (and Morocco), godwits currently staging in Iberia are predicted to fly directly to The Netherlands and be present at breeding locations earlier than previously expected and observed. Despite harbouring approximately 75% of the total population during spring migration, Iberian staging sites currently lack any legal protection. Our example of the Black-tailed Godwit illustrates the potential of this approach to identify migration strategies and locate staging sites for species of conservation concern for which such information may be virtually absent.

Migratory species rely on several distant sites during the annual cycle which makes their conservation more complex than that of non-migratory species. Even one of the most extensively studied migratory shorebirds - the Red Knot Calidris canutus - is currently ‘Near Threatened’ at the global level. Conflicting observations of migratory routes cast uncertainty on the subspecies classification and migratory connectivity of Red Knots in the Pacific coasts of the Americas. To fill essential information gaps, we present the first detailed population morphometrics of Red Knots during the non-breeding season in the southern Pacific coast, along with resightings of these birds throughout the Americas. We also estimated daily rate of weight gain during fuelling based on body mass at captures and known departure dates. Resightings demonstrate reliance on staging areas in both the Mid-continental and Atlantic flyways during the northward migration, and additionally in the Pacific Flyway during southward migration. In addition to the strong connection with several areas also used by C. c. rufa on the North American Atlantic coast, our results show morphometric differences within the ranges of both C. c. rufa and C. c. roselaari. Given the threats faced by Red Knots, the population in Chiloé Archipelago should be treated as a separate conservation unit within interhemispheric conservation programmes for endangered shorebirds within the Americas.

The increasing pressure of anthropogenic development in areas with high natural value poses a huge challenge for wildlife conservation worldwide. The Tagus estuary in southern Portugal is among the most important wetlands for migratory shorebirds in the East Atlantic Flyway (EAF). However, in 2020 the Portuguese government approved the construction of the new Lisbon international airport at the heart of the Tagus estuary. Intense aircraft traffic, flying at low altitudes during both approach and take-off, is expected to cross the estuary, overlapping to a great extent the important intertidal foraging areas. Here, we aim to quantify the potential loss of conservation value of the intertidal areas of the Tagus estuary for shorebirds resulting from the disturbance (noise) caused by overflying aircraft. Using a comprehensive dataset of wintering shorebird abundance and distribution in the whole intertidal estuarine area we first identified priority areas for conservation using a spatial prioritization approach. We then performed a replacement cost analysis by excluding the areas likely to become unsuitable or severely underused by birds due to intense air traffic noise. Our results suggest that the implementation of the new Lisbon airport may lead to a loss of up to 30% of the conservation value of the Tagus estuary in terms of intertidal feeding areas of wintering birds alone. The global impact will likely be greater when effects on supratidal roosts, as well as on passage birds, are also considered. The Tagus estuary, which is internationally important for six of the 10 species included in our analysis, is just one of a network of already depleted sites along the EAF. Thus, negative impacts on bird populations on the Tagus estuary will have repercussions and undermine conservation efforts elsewhere. The plight of shorebirds at the Tagus estuary is thus a matter of international conservation concern.

A narrow coastal plain located between the Greater Caucasus and the Caspian Sea was recently discovered to be a major avian flyway through Transcaucasia. Here at the Besh Barmag bottleneck in Azerbaijan an estimated 1.24–1.51 million migrants passed through in autumn 2011 and a further 0.65–0.82 million in spring 2012, elevating this bottleneck to international importance. Furthermore, 34 bird species were observed in numbers in excess of the 1% threshold of world or flyway population in at least one of the observation seasons. Due to the high concentration of these species, any dangers affecting this passage can be threatening at a population scale. This study therefore aims to describe the migratory behaviour of these 34 species and subsequently to identify the dangers involved in passage through the area. Collision with anthropogenic obstacles was regarded as the main threat in the coastal plain. Ten (40%) of the species studied and observed in autumn 2011 were flying at the lowest altitudes and are therefore under threat on migration through the bottleneck due to overhead power lines, buildings, traffic and hunting. Planned infrastructural developments with heights of up to 200 m (e.g. towers, wind farms) pose a future threat for an additional 13 (52%) of the study species observed in autumn, making a total of 23 species that would be threatened. Only two species, Pygmy Cormorant Microcarbo pygmaeus and Grey Heron Ardea cinerea, can be expected to maintain their currently safe passage in future as they migrate mainly above 200 m above ground level. In spring 2012, all 14 (100%) of the species that used the coastal plain as flyway, migrated below 50 m and are therefore imminently threatened by collision. Although birds migrating over the Caspian Sea were concentrated at the lower altitudes, there was no identifiable threat for migrants using this flyway, but hazards can be expected in the oil production areas further south.

We documented the geographical distributions and habitat selection of Neotropical migrants in South America along a successional gradient in the lowlands of Amazonian Peru, and along elevational gradients in the Andes of south-eastern Peru and of eastern and western Ecuador. Most of the 30 species of northern migrants that regularly winter in South America appear to be concentrated in the western edge of the Amazon basin and on the lower slopes (2,000 m) of the Andes. Migrants in a lowland site were documented more often in early successional habitats than in primary forest, and no species were confined to mature forest habitats. The number of species and relative abundance of migrants in primary forest, however, increased with elevation up to about 1,200 m and decreased above that elevation. Several species (Contopus borealis, Dendroica cerulea and Wilsonia canadensis) were largely confined to primary forest in the 1,000-2,000 m elevational zones in both Peru and Ecuador. Migrants on the western slope of the Ecuadorean Andes included several species that primarily winter further north. In general, the species richness of migrants and residents was inversely correlated, both on a biogeographical and a local scale. Migratory birds are most likely to be adversely affected by deforestation of the lower slopes of the Andes, which is proceeding at a rapid pace. The impact of human alterations of Amazonian forests will be greater on resident than on migratory birds. The loss of mid-successional lowland forests, however, might have a negative effect on several species.

The study area at Zait Bay, Egypt (c. 700 km2) is situated in the middle of the West Asian-East African migration flyway used by very large numbers of soaring migrants. At this site the corridor narrows into a bottleneck. There exist only very few bottlenecks of this magnitude in the world. Observations were performed at all hours between sunrise and sunset at 26 observation sites, situated 5 km apart. The northern part of the area under investigation (19 observation sites) was situated within the Gebel El Zeit IBA (criteria A1 and A4iv), while the southernmost part (8 observation sites) was outside. The overall evaluation has shown that 179,681 soaring birds including 122,454 storks and 36,976 raptors were observed in total. Within a radius of 2.5 km from each observation site 97,143 soaring birds including 59,308 storks and 30,489 raptors were observed during the 604 hours of observation. Eleven species were recorded in numbers that exceed 1% of their flyway populations. Of special concern regarding bird conservation are those birds resting or flying in the first 200 m of elevation. In total 6,624 soaring birds were seen resting (2,252 within a radius of 2.5 km). Thirty-three percent of the storks and 47% of the raptors were observed resting or flying at heights within the lowest 200 m. The median height of flying birds varied between 5 m (harriers) and 500 m (Common Crane Grus grus). According to the raw data, criteria for nomination of the area as an IBA (20,000 raptors and storks in one migration season, globally threatened species) were fully met outside the existing IBA. Also, to the south of the study area, very high numbers of migrants were confirmed by spontaneous, non-systematic observations. Accordingly, a change of the boundaries is suggested. The regional analysis, based on extrapolations, has to be regarded as a preliminary study. The analysis failed to show a geographical trend for any single species. The data from this study establish a high concentration of gliding and soaring birds in the study area, within and adjacent to the already designated IBA.

Migratory wader populations face global threats, mainly related to increasing rates of habitat loss and disturbance driven by human activities. To a large extent, the long-term survival of these populations requires the conservation of networks of sites along their migratory flyways. The Tagus estuary, Portugal, is among the most important wetlands for waders in the East Atlantic Flyway. Annual winter wader counts have been carried in this wetland since 1975 and a monthly roost-monitoring programme was implemented in 2007. Wintering populations of three out of the five most abundant species, Dunlin Calidris alpina, Grey Plover Pluvialis squatarola and Redshank Tringa totanus, showed significant population declines over the past three decades, which are most likely due to the loss and degradation of roost sites as a result of increasing human activity. The situation is unlikely to improve, as a high proportion of the wintering waders use roost sites that are situated in highly urbanised areas with no legal protection. The use of different roost sites by waders is highly variable both temporally and spatially, thus emphasizing the need for a network of good quality roost sites. Additionally, during migration, 60–80% of all the waders of the Tagus estuary concentrate at a single refuge, thus increasing the risk for wader populations during these periods.

Because migrant birds occur in different parts of the world in different seasons, their numbers may be limited by the size of the smallest area they inhabit during the year. In addition, restricted ranges make populations more susceptible to local perturbations such that range size is frequently considered a correlate of species vulnerability. Despite this, little is known about the balance between seasonal ranges in the migrant populations of partially migratory species. These migrants are difficult to segregate from sedentary conspecifics in winter grounds and thus the extent of their ranges is difficult to assess. Here, we studied the extent of potential breeding and wintering ranges of 10 partial migratory passerines moving to winter in the Iberian Peninsula and the Maghreb. After testing migratory connectivity of the individual species, we used niche modelling to calculate the extent of potential breeding and wintering ranges in 1,113 pairs of ring recoveries linking individuals between breeding and wintering localities. The results indicate that most species show migratory connectivity and that all of them show range compression in winter relative to the breeding range, with scores ranging between 19% and 58% (mean 37%) of breeding ranges. We discuss the importance of non-breeding grounds for conserving migratory passerines in the Western Mediterranean Basin, an area under pressure from climate change and agricultural intensification.

The Sahel in West Africa is a major wintering area for many western Palearctic migrants. The breeding populations of many of these have declined over the past 50 years. However, there have been few intensive field studies on migrant ecology in the Sahel and these were generally within a very restricted area. Consequently our knowledge of the distribution of species within this extensive area and the habitat associations of these species is limited. Understanding these habitat associations is essential for the effective conservation management of populations. We brought together a group of experts and consulted a wider group by email to assess the main Sahelian habitat types used by 68 African-Eurasian migrant bird species. Those species that showed strongest declines during 1970–1990 were associated with more open habitats than those newly declining during 1990–2000, when declining species were associated with habitats with more shrubs and trees. Populations of species that winter in the Sahel are generally stable or increasing now as rainfall has increased and is now near the long-term average for the Sahel. Those which use the Sahel only as a staging area are, in many cases, in rapid decline at present.

Birds that are long-distance migrants partition their annual cycle among a number of locations over a large spatial range. The conservation of these species is particularly complex because it requires attention to a number of different and distant habitats based on knowledge of migratory phenology, routes and staging areas. In the case of the globally threatened Aquatic Warbler Acrocephalus paludicola, a habitat specialist that breeds in Europe and spends the boreal winter in sub-Saharan Africa, non-breeding staging areas were widely unknown until recently. We applied light-level geolocators to adult male Aquatic Warblers at breeding sites in Belarus and Ukraine. Data from eight retrieved geolocators confirmed a south-west and then westward migration route through Europe via the northern Mediterranean with staging sites on the Iberian Peninsula and occasionally France and north-west Africa. In sub-Saharan Africa, final staging areas were in Mali, either in the Inner Niger Delta or at (presumably) small water bodies in the desert, with one bird most likely staying in the north of Ivory Coast south of the previously assumed range. The birds probably stayed in the final staging areas for most of the non-breeding season, but the logger on only one bird provided data throughout the entire migration cycle. Pre-nuptial migration of the latter was by a more easterly route than the southward migration. Our study suggests that conservation strategies for Aquatic Warbler north of the Sahara should include consideration of unknown staging sites in the northern Mediterranean as well as on the Iberian Peninsula and in north-west Africa. South of the Sahara, our study demonstrates the importance of the Sahel for the conservation of the Aquatic Warbler, including both the major floodplains of the Niger River and small Sahelian wetlands that are under pressure from human development.