Joanna B. Wong

Countries have committed to expanding the marine protected area (MPA) network to 30% of the world's ocean by 2030, more than tripling current coverage, and focusing on areas important for biodiversity. For such expansion to translate into effective conservation of marine biodiversity, it must rely on the best available knowledge. Here, we analyze tracking data on > 13,000 individuals (44 species, eight families) to map the distribution of highly mobile seabirds in the Atlantic Ocean and adjacent seas throughout the year. We identify regions important year‐round or seasonally. The High Seas are as important as national waters for highly mobile seabirds but are even less protected. Current Atlantic MPAs hold < 14% of tracked species density, but their expansion to 30% of the ocean could protect up to two thirds. We share this new knowledge layer to support national and international efforts and policies to strategically expand the Atlantic MPA network.

Many migratory animals use spatial variation in the Earth's magnetic field for orientation and navigation. This raises the possibility of exploiting these same cues to geolocate and track migratory animals throughout their annual journeys. Magnetic‐based geolocation could be particularly valuable for small aerial and aquatic species, for which the most precise pressure‐based geolocation cannot be applied. We developed a novel geolocation method, implemented in the R package GeoMagR ( https://geopressure.org/GeoMagR/ ) that uses three‐axis magnetic field measurements from lightweight multi‐sensor tags. The workflow consists of: (i) tilt compensation and magnetic calibration; (ii) extraction of time series of magnetic intensity and inclination; and (iii) generation of spatial likelihood maps using the World Magnetic Model (WMM). We evaluated the method using field data to assess achievable spatial precision and potential complementarity with other geolocation techniques. Magnetic geolocation achieved a typical spatial accuracy of ~150 km in latitude but provided little constraint in longitude. When combined with light‐based geolocation, which offers high longitudinal accuracy but poor latitudinal resolution, the integration markedly improved overall position estimates. Magnetic geolocation is a viable complementary tool for tracking small avian species, particularly in contexts where pressure‐based methods cannot be used. By independently resolving latitude, it enhances spatial inference when integrated with other geolocation data sources. This processing of 3D magnetic and acceleration data from geolocators also extends their use beyond positioning, enabling applications in studies of behaviour and navigation.

Understanding how migratory birds balance energetic costs of movement with wintering benefits requires quantifying their energy expenditure across the full annual cycle. Here, we present a novel approach to reconstruct annual energy budget from multi-sensor geolocator data on atmospheric pressure and activity. We apply this method to tracking data of Eurasian Wrynecks from a European breeding population exhibiting striking variation in migration distance: short-distance migration to southern Europe, medium-distance to northern Africa, and long-distance to sub-Saharan Africa. Long-distance migrants had 21-26% lower annual energy expenditure than shorter-distance migrants, primarily due to reduced thermoregulation costs during boreal winter. However, they faced extreme physiological demands during migration, with daily energy expenditure exceeding 9.5 times basal metabolic rate. Since 1950, climate warming has progressively reduced winter thermoregulation demands disproportionately benefiting and potentially promoting shorter-distance strategies. These results reveal shifting energetic trade-offs under climate change, potentially driving evolution of migration patterns.

Understanding migration strategies in closely related species is essential to assess population-specific threats and to identify the ecological drivers of speciation. To compare migration strategies and environmental conditions across the annual cycle, we tracked Western Black-eared Wheatears, Eastern Black-eared Wheatears and Pied Wheatears. Individual migration routes were reconstructed from multi-sensor loggers and light-level geolocator data. Western Black-eared Wheatears breeding in Spain migrated south-west to Mauritania and Mali, overwintering at a single site in arid regions at the Sahara’s edge. Eastern Black-eared Wheatears breeding in Greece crossed the Mediterranean and Sahara to reach the Sahel, using single non-breeding sites in Nigeria, Chad, and Niger, much further west than previously assumed. Pied Wheatears breeding in Romania migrated via Turkey and the Arabian Peninsula, and overwintered in Somalia, with some individuals shifting sites during winter. Migration strategies differed: Eastern Black-eared Wheatears performed large-scale loop migration. Pied Wheatears used direct routes and did not follow their presumed former range expansion around the Black Sea. Environmental data suggested that non-breeding conditions contrasted stronger than breeding conditions: Western Black-eared Wheatears occupied arid non-breeding sites at the edge of the Sahara that remained dry throughout their stay, Eastern Black-eared Wheatears arrived in the Sahel at the end of the rainy season, and Pied Wheatears had two rainy seasons in the Horn of Africa. These results highlight distinct migration strategies and non-breeding conditions in three closely related wheatears, underlining the importance of species-specific or even population-specific tracking to refine non-breeding range delineation and inform conservation.

The natural history of migration comprises a set of population-specific ecological and flexible traits, that will undergo fundamental changes under current climate alterations, but basic features remain undiscovered for many species and populations. Here, we provide the first spatiotemporal annual cycle information of individual Tree Pipits ( Anthus trivialis ), one of the most common long-distance African-Palearctic migrants. Male pipits from Czechia showed a large variation in migration routes and African nonbreeding residence sites. In autumn, birds crossed the Mediterranean basin over a wide range from its western to eastern part to reach nonbreeding sites in West Africa, Nigeria, and the Lake Chad area. Nonbreeding residence period lasted on average 160 days, wherein 28% of males showed site itinerancy of 100 km and 400 km between overwintering sites. Northbound spring migration routes differed entirely or in the North-African European portion from autumn (post-breeding) routes, resulting in seasonally different passage regions. Departure periods from the breeding sites in autumn and the nonbreeding sites in spring spanned over a 1.5- and 1 month period, respectively. Migration duration per bird in spring lasted 20 days (median) which was 61% shorter than the duration of autumn migration (median: 52 days). Our study shows that Tree Pipits from a single breeding population pass through and reside across vast areas and thus, experience a wide array of environmental conditions outside their breeding season. To establish a causal link between environmental conditions and the population trajectory of Tree Pipits, further tracking information are required especially from northern and eastern European breeding populations.

Although geolocator tracking of small passerines has become commonplace in the last two decades, this tool is still underutilized for gathering natural history data of migration in many species. Common Whitethroat (Curruca communis) is one of the most numerous Afro-Palearctic migrants. However, our knowledge of the species’ migration ecology remains limited. Here, we combine ring-recovery analyses with geolocator tracking to describe migration routes and population-specific non-breeding areas in this long-distance migrant. Linkages between breeding, passage and non-breeding areas based on ring-recovery records revealed a strong correlation in longitudes, indicating parallel migration system and population-specific non-breeding grounds in whitethroats. Migration route simulation using EURING data suggested a possible migratory divide in Central Europe in autumn, while broad front migration across the Mediterranean occurs in spring. Geolocator-tracked whitethroats from Czechia (Central Europe) and Latvia (North-eastern Europe) migrated to non-breeding sites in Central Africa, where they first resided in the Sahel region before moving farther to a second non-breeding site in November/December. Major stopovers were associated with crossing of ecological barriers. A single Latvian bird with a repeat track showed similar migration patterns in both years, possibly visiting the same non-breeding sites in consecutive years. Both ringing and tracking data revealed clockwise loop migration between breeding and non-breeding sites.

The barred warbler, Curruca nisoria, is an Afro-Palearctic migrating bird with a wide breeding distribution across eastern Europe to central Asia. Ring recoveries and direct observations have suggested they migrate to non-breeding grounds in East Africa. However, little is known about their migration routes and flight behaviour during migration and on the non-breeding grounds. Using geolocators and multi-sensor loggers, we tracked three barred warblers from a Czech breeding site to document their migration routes, stopover and non-breeding sites, and flight activity patterns across the annual cycle. All three tracked birds took south-eastern autumn migration routes through the Levant, with a shared stopover in Syria before crossing the Arabian Desert, the Red Sea and eastern Sahara Desert and stopping in Sudan for ca. two months. After 109 days (average), birds arrived at their main non-breeding sites of W Kenya or S Ethiopia. A single stopover on the Red Sea coast of Saudi Arabia was used during the spring migration before continuing NW across the Mediterranean. Pressure and acceleration data showed that warblers migrated exclusively at night, with the longest flights crossing the Sahara and travelling from Sudan to non-breeding sites. Daily diurnal activity patterns were uniform across all stationary sites.

The Lesser Grey Shrike is a typical Palaearctic songbird for which we have limited knowledge of its migration ecology. All that is known about its non-breeding movements is inferred from observational data of birds on passage. The few available ring recovery data do not link breeding and African non-breeding grounds. By deploying two types of loggers, light-level geolocators and multi-sensor loggers, on birds from a declining Slovak breeding population, we present the first direct evidence for non-breeding grounds, loop migration, stopover sites and the timing of annual cycle events. With barometric data, we provide details on flight altitudes during migration. The two tracked birds migrated in a clear anti-clockwise loop to S Africa. Autumn migration tracks went through the Balkan Peninsula, Mediterranean Sea towards Libya with unusually long stays around N Chad and Niger. The next stopovers were in Angola, and the main non-breeding sites were in Botswana. Spring migration commenced on March 29 and April 7 and the birds took routes along East African countries, with stopovers later in Somalia and Saudi Arabia, before crossing the eastern Mediterranean Sea. Nocturnal migration dominated, but for three days in August, while crossing the Sahara Desert, the bird extended flights into the day with a sudden increase in flight altitudes at dawn. Flight altitudes were higher during barrier crossing and during the last phase of spring migration compared to the remaining periods, with the most extreme event recorded at 4530 m asl.

Arctic ecosystems are changing rapidly. The tundra supports nesting migratory seabirds that spend most of their year over the ocean. Migrations are demanding, but it is unclear how physiological capability may equip organisms to respond to their changing environments. For two migratory seabird species nesting in Alaska, USA, the Arctic tern (n = 10) and the long-tailed jaeger (n = 8), we compared oxidative physiology and aerobic capacity measured during incubation and we recorded individual movement paths using electronic tracking tags. Within species, we hypothesized that individuals with longer-distance migrations would show higher oxidative stress and display better aerobic capacity than shorter-distance migrants. We examined blood parameters relative to subsequent fall migration in jaegers and relative to previous spring migration in terns. We present the first measurements of oxidative stress in these species and the first migratory movements of long-tailed jaegers in the Pacific Ocean. Arctic terns displayed positive correlation of oxidative variables, or better integration than jaegers. Relative to physiological sampling, pre-breeding northward migration data were available for terns and post-breeding southward data were available for jaegers. Terns reached a farther maximum distance from the colony than jaegers (16 199 ± 275 km versus 10 947 ± 950 km) and rate of travel northward (447 ± 41.8 km/day) was positively correlated with hematocrit, but we found no other relationships. In jaegers, there were no relationships between individuals’ physiology and southward rate of travel (193 ± 52.3 km/day) or migratory distance. While it is not clear whether the much longer migrations of the terns is related to their better integration, or to another factor, our results spark hypotheses that could be evaluated through a controlled phylogenetic study. Species with better integration may be less susceptible to environmental factors that increase oxidative stress, including thermal challenges or changes in prey distribution as the Arctic climate changes rapidly.