Autumn Migration Routes Research Articles

Autumn migration of black-necked crane (Grus nigricollis) on the Qinghai-Tibetan and Yunnan-Guizhou plateaus.

Despite previous research efforts, the majority migration routes of the black-necked cranes (Grus nigricollis) have remained veiled. In this study, we utilized satellite telemetry data from 45 cranes between 2015 and 2021 to unveil critical insights. Our results revealed 11 distinct autumn migration routes and one sedentary flock, of which eight routes and the sedentary flock were previously undocumented. Our findings highlighted the remarkable diversity in the migration routes of black-necked cranes, especially in terms of migration orientations, spatial-temporal patterns, and altitudinal movement patterns. Cranes breeding on the eastern, northern, and central Qinghai-Tibetan Plateau migrated southward, while those on the northern slopes of the Himalayas migrated eastward, westward, northward, or opted to remain sedentary. Moreover, we expanded the known range of migration distances to 84-1520 km at both ends (excluding sedentary individuals) and identified two long-term (Da Qaidam and Chaka) and one short-term (Gyatong grassland) stopover sites. Furthermore, our study revealed that the breeding colonies in the Qilian Mountains on the northeastern Qinghai-Tibetan Plateau utilized long-term stopover sites before embarking on significant altitude ascent, while other flocks displayed more urgent migration patterns, preferring to roost only at night. By unveiling the near-complete autumn migration routes of black-necked cranes, our research has contributed to discovering the critical habitats and connectivity among various breeding colonies, which is instrumental in developing effective seasonal conservation plans.

Life-cycle analysis of an endangered migratory goose to assess the impact of conservation actions on population recovery

Evaluating the effectiveness of conservation actions is challenging for migratory species because a population can be impacted anywhere along its route. Conservation actions for the critically endangered Fennoscandian lesser white-fronted goose population include culling of red foxes in the breeding area and habitat improvements and reduction of illegal hunting in the non-breeding areas. One goal of the predator control strategy is to prevent adult birds from using an autumn migration route through western Asia, where mortality is believed to be higher than on the migration route through eastern Europe. We used 23 years of count data obtained at different staging areas to parameterize a seasonal state-space model describing the full-annual cycle dynamics of this population and evaluate whether the recent population recovery was linked to these conservation efforts. The results did not provide evidence that predator control influenced population recovery, as survival on the European route did not appear higher than on the allegedly riskier Asian route. However, adult survival at staging areas on both routes and at wintering sites may have improved in the last decade, suggesting a positive effect of the other conservation initiatives. These results emphasize the importance of including the non-breeding dynamics in population assessments of migratory species and highlight the challenge of evaluating the efficacy of separate conservation actions when a proper experimental design is unfeasible. Our study, which is a unique case of cross-national, coordinated conservation efforts, exemplifies how to model complex population dynamics to assess the influence of costly conservation initiatives.

Loop-migration and non-breeding locations of British breeding Wood Warblers Phylloscopus sibilatrix

ABSTRACT Capsule: British breeding Wood Warblers Phylloscopus sibilatrix show a clockwise loop migration incorporating stops in southern Europe, the Sahel, and the humid forest zone of West Africa. Aims: To determine autumn and spring migration routes, the location and duration of stopover sites on migration, and the location of non-breeding areas of British breeding Wood Warblers. Methods: In 2016 and 2018 we deployed geolocators to male Wood Warblers on Dartmoor, Devon, and in the New Forest, Hampshire. We retrieved four geolocators from returning birds in 2017, 2019, and 2020. Results: Male Wood Warblers departed breeding sites in late July and stopped for most of August in central southern Europe, crossed the Sahara by a non-stop night and day flight immediately followed by a short stop, and then migrated west to a longer stopover in the Sahel. Final non-breeding destinations were in an area of West Africa covering Guinea, Sierra Leone, and Liberia. Two were tracked on spring migration, again crossing the Sahara via a non-stop flight before migrating through Western Europe to complete a clockwise loop migration back to Britain. Conclusion: All tracked Wood Warblers used stopovers for at least three weeks in three distinct regions, in central southern Europe, in the Sahel, and in the humid zone of West Africa. Although the limitations of geolocation prevent matching locations with habitat, these regions are broadly characterized by distinct forest or woodland habitat types, which differ from breeding habitat. All four tracks showed similar patterns in route, stopover behaviour, and timings, suggesting they may be representative of males in these breeding populations, and potentially of other British and western European Wood Warbler populations.

Autumn migration routes of fledgling Chinese Egrets (Egretta eulophotes) in Northeast China and their implications for conservation

The Chinese Egret (Egretta eulophotes) is a globally threatened bird species living on the coast and islands of Liaoning, northeastern China, mainly in summer. To further protect the breeding population of Chinese Egrets, it is important to understand the current protection status of their distribution sites at pre-migration period and migration routes. Thirty-three individuals were tagged with satellite transmitters at Fantuo Island in Changhai and Xingren Island in Zhuanghe, Liaoning Province, northeastern China, in July of 2016, 2017, and 2018, to identify important distribution sites during the pre-migration period, as well as detailed migration routes. The results showed that coastal mudflats in Liaoning and the west coast of North Korea were important feeding and roosting sites for fledgling Chinese Egrets from August to September. The home range sizes in August were significantly larger than in September. The eastern coast from Shandong to Guangdong, as well as Taiwan, China, and Manila Bay and Galileo Islands in the Philippines, were important stopover sites during fall migration. Specifically, we found that the egrets’ autumn migration could be divided into four routes, i.e., sea-crossing migration (SCM), coastal migration (CM), inland migration (IM), and mixed migration (MM). The migration distance, timing, speed, and straightness of the four routes also differed. The SCM routes were the straightest, and had the fastest migration speed and shortest travel time, while the IM routes had the lowest straightness and speed, and the longest duration. Manila Bay and Bohol Island in the Philippines, the west coast of Tanintharyi in Myanmar, and the Zengwun River Estuary in Taiwan, China, were wintering sites. Our findings on the key distribution sites along pre-migration and fall migration routes, including some stopover sites, have important implications for the conservation of and global action plan development for the vulnerable Chinese Egret.

Autumn migration routes and wintering areas of juvenile Chinese Egrets (Egretta eulophotes) revealed by GPS tracking

BackgroundThe vulnerable Chinese Egret (Egretta eulophotes) is a long-distance migratory waterbird whose migration and wintering information is poorly understood. This study aims to identify the autumn migration routes and wintering areas of juvenile Chinese Egrets and determine the migration movement traits of this species.MethodsThirty-nine juvenile Chinese Egrets from the Fantuozi Island, an uninhabited offshore island with a large breeding colony of Chinese Egrets in Dalian, China, were tracked using GPS/GSM transmitters. Some feathers from each tracked juvenile were collected for molecular identification of sex in the laboratory. The GPS locations, recorded at 2-h intervals from August 2018 to May 2020, were used for the analyses.ResultsOf the 39 tracked juveniles, 30 individuals began their migration between September and November, and 13 successfully completed their autumn migration between October and November. The juveniles migrated southward via three migration routes, coastal, oceanic and inland, mainly during the night. The migration duration, migration distance, flight speed, and stopover duration of the 13 juvenile egrets that completed migration averaged 5.08 ± 1.04 days, 3928.18 ± 414.27 km, 57.27 ± 5.73 km/h, and 23.08 ± 19.28 h, respectively. These juveniles wintered in the coastal wetlands of Southeast Asia including those in the Philippines, Vietnam, and Malaysia, and only one successfully began its spring migration in June 2020.ConclusionsThis study newly finds that the oceanic route taken by juvenile Chinese Egrets, suggesting that the juveniles are able to fly over the Pacific Ocean without a stopover. Moreover, our novel data indicate that coastal wetlands along the East Asian–Australasian Flyway are important areas for both autumn migration stopover and the wintering of these juveniles, suggesting that international cooperation is important to conserve the vulnerable Chinese Egret and the wetland habitats on which it depends.

Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird.

Many migratory species are declining and for most, the proximate causes of their declines remain unknown. For many long-distance Neotropical migratory songbirds, it is assumed that habitat loss on breeding or non-breeding grounds is a primary driver of population declines. We integrated data collected from tracking technology, community science and remote sensing data to quantify migratory connectivity (MC), population trends and habitat loss. We quantified the correlation between forest change throughout the annual cycle and population declines of a long-distance migratory songbird, the Connecticut warbler (Oporornis agilis, observed decline: -8.99% yr-1). MC, the geographic link between populations during two or more phases of the annual cycle, was stronger between breeding and autumn migration routes (MC = 0.24 ± 0.23) than between breeding and non-breeding locations (MC = -0.2 ± 0.14). Different Connecticut warbler populations tended to have population-specific fall migration routes but overlapped almost completely within the northern Gran Chaco ecoregion in South America. Cumulative forest loss within 50 km of breeding locations and the resulting decline in the largest forested patch index was correlated more strongly with population declines than forest loss on migratory stopover regions or on wintering locations in South America, suggesting that habitat loss during the breeding season is a driver of observed population declines for the Connecticut warbler. Land-use practices that retain large, forested patches within landscapes will likely benefit breeding populations of this declining songbird, but further research is needed to help inform land-use practices across the full annual cycle to minimize the impacts to migratory songbirds and abate ongoing population declines.

Autumn Migration Route and Stopover Sites of Black-Necked Crane (Grus nigricollis) Breeding in Yanchiwan Nature Reserve, China

From July to November 2018, 10 Black-necked Crane (Grus nigricollis) juveniles were tracked using GPS-GSM satellite transmitters to study their migration routes and stopover sites in Yanchiwan Nature Reserve, Gansu Province, China. By the end of the autumn migration in November 2018, more than 25,000 GPS locations had been obtained during tracking. Migration routes, migration distances and stopover sites were determined, and the stopover home range was estimated for each individual. Individuals moved away from Yanchiwan during 2-25 October 2018 and migrated through Da Qaidam, Golmud City, Qumarleb County, Zadoi County, Zhidoi County, and Nagqu City. In mid-November 2018, the birds arrived in Linzhou County, Tibet, China to winter. The migration routes of all individuals were the same, and the average migration distance was 1,500 ± 120 km. Da Qaidam Salt Lake was an important stopover site, with an average stopover duration of 27.11 ± 8.43 d, and the average stopover range of the Black-necked Cranes at Da Qaidam was 27.4 ± 6.92 km2. Through field monitoring and satellite maps, the main habitats were determined to be grasslands and wetlands.

Migration routes and strategies of Grey Plovers (Pluvialis squatarola) on the East Atlantic Flyway as revealed by satellite tracking

BackgroundWhile the general migration routes of most waders are known, details concerning connectivity between breeding grounds, stopover sites and wintering grounds are often lacking. Such information is critical from the conservation perspective and necessary for understanding the annual cycle. Studies are especially needed to identify key stopover sites in remote regions. Using satellite transmitters, we traced spring and autumn migration routes and connectivity of Grey Plovers on the East Atlantic Flyway. Our findings also revealed the timing, flight speed, and duration of migrations.MethodsWe used ARGOS satellite transmitters to track migration routes of 11 Grey Plovers that were captured at the German Wadden Sea where they had stopped during migration. Birds were monitored for up to 3 years, 2011‒2014.ResultsMonitoring signals indicated breeding grounds in the Taimyr and Yamal regions; important staging sites on the coasts of the southern Pechora Sea and the Kara Sea; and wintering areas that ranged from NW-Ireland to Guinea Bissau. The average distance traveled from wintering grounds to breeding grounds was 5534 km. Migration duration varied between 42 and 152 days; during this period birds spent about 95% of the time at staging sites. In spring most plovers crossed inland Eastern Europe, whereas in autumn most followed the coastline. Almost all of the birds departed during favorable wind conditions within just 4 days (27‒30 May) on northward migration from the Wadden Sea. In spring birds migrated significantly faster between the Wadden Sea and the Arctic than on return migration in autumn (12 vs. 37 days), with shorter stopovers during the northward passage.ConclusionsOur study shows that satellite tags can shed considerable light on migration strategies by revealing the use of different regions during the annual cycle and by providing detailed quantitative data on population connectivity and migration timing.

Новое «узкое место» на осеннем миграционном маршруте хищных птиц через Каракорум

С 70-х гг. казахстанскими орнитологами на перевале Чокпак в предгорьях Западного Тянь-Шаня вёлся регулярный учёт мигрирующих птиц, на основании которого стала понятна особая важность данного участка для мигрантов из Южной и Средней Сибири. Дальнейшие исследования миграции крупных хищных птиц посредством спутниковой телеметрии и GPS/GSM-трекинга лишь подтвердили предположение о том, что большая часть крупных хищных птиц из Алтае-Саянского региона (даже из восточной части Республики Тыва), летит на Аравийские, Иранские, Пакистанские и Индийские зимовки в обход высокогорий Тянь-Шаня и Памиро-Алая, проходя первое на своём пути наиболее масштабное «бутылочное горлышко» преимущественно в 150-ти километровом коридоре через Каратау на границе Казахстана и Киргизии. Тем не менее, некоторые хищные птицы, причём трёх разных видов, показали движение через высокогорный район Кунь-Луня, Каракорума и Гималаев, на котором акцентировано внимание в данном сообщении.

Representing migration routes from re-encounter data: a new method applied to ring recoveries of Barn Swallows (Hirundo rustica) in Europe

Bird ringing was established more than a century ago to gather information on bird movements. Since then, ornithologists have systematically collected huge databases of records of birds ringed and subsequently re-encountered, but, to date, there have been few quantitative attempts to identify migratory routes from ringing data. Here, we develop a novel, quantitative method for describing migration routes using ringing data and we applied it to a dataset of 72,827 ring recoveries of the Barn Swallow (Hirundo rustica) through western and central Europe from the EURING and SAFRING databanks spanning 1908–2011. We considered movements of 332 individuals during spring migration and 1509 during autumn migration. The results indicate that, in spring, Barn Swallows enter western Europe through Gibraltar or by crossing the Mediterranean Sea through the Balearic Islands, Sardinia, and the Italian peninsula. They then spread over a wide front. In northern France, Belgium and the Netherlands routes diverge, pointing toward either the British Isles or Denmark and Scandinavia. Autumn migration routes are similar to those in spring. The general migration pattern that emerged from the analyses was consistent with previous descriptions of migratory movements of this well-known species. However, this analysis also revealed some previously undocumented migration patterns. For instance, in spring, some migrants moved from the Balearic Islands to Corsica and Italy, thus making a rather long eastward crossing of the Mediterranean Sea. In autumn, some migrants moved from the Balkan Peninsula westwards toward Italy. Analyses restricted to recoveries within the same spring or the same autumn and to birds found dead showed similar patterns. Our procedure was, therefore, able to identify migration patterns over a large geographical area, and may be extended to those species for which large datasets of ring recoveries or sight-resight data are available.

Ten grams and 13,000\xa0km on the wing \u2013 route choice in willow warblers Phylloscopus trochilus yakutensis migrating from Far East Russia to East Africa

BackgroundHigh-latitude bird migration has evolved after the last glaciation, in less than 10,000–15,000 years. Migrating songbirds rely on an endogenous migratory program, encoding timing, fueling, and routes, but it is still unknown which compass mechanism they use on migration. We used geolocators to track the migration of willow warblers (Phylloscopus trochilus yakutensis) from their eastern part of the range in Russia to wintering areas in sub-Saharan Africa. Our aim was to investigate if the autumn migration route can be explained by a simple compass mechanism, based on celestial or geomagnetic information, or whether migration is undertaken as a sequence of differential migratory paths possibly involving a map sense. We compared the recorded migratory routes for our tracked birds with simulated routes obtained from different compass mechanisms.ResultsThe three tracked males were very similar in the routes they took to their final wintering sites in southern Tanzania or northern Mozambique, in their use of stopover sites and in the overall timing of migration. None of the tested compass mechanisms could explain the birds’ routes to the first stopover area in southwest Asia or to the destination in Southeast Africa without modifications. Our compass mechanism simulations suggest that the simplest scenarios congruent with the observed routes are based on either an inclination or a sun compass, assuming two sequential steps.ConclusionsThe birds may follow a magnetoclinic route coinciding closely with the tracks by first moving west, i.e. closer to the goal, and thereafter follow a constant apparent angle of inclination to the stopover site. An alternative would be to use the sun compass, but with time-adjustments along the initial part of the migration to the first stopover, and thereafter depart along a new course to the winter destination. A combination of the two mechanisms cannot be ruled out, but needs to be confirmed in future studies.

Around the Mediterranean: an extreme example of loop migration in a long‐distance migratory passerine

An important issue in migration research is how small‐bodied passerines pass over vast geographical barriers; in European–African avian migration, these are represented by the Mediterranean Sea and the Sahara Desert. Eastern (passing eastern Mediterranean), central (passing Apennine Peninsula) and western (via western Mediterranean) major migration flyways are distinguished for European migratory birds. The autumn and spring migration routes may differ (loop migration) and there could be a certain level of individual flexibility in how individuals navigate themselves during a single migration cycle. We used light‐level loggers to map migration routes of barn swallows Hirundo rustica breeding in the centre of a wide putative contact zone between the northeastern and southernwestern European populations that differ in migration flyways utilised and wintering grounds. Our data documented high variation in migration patterns and wintering sites of tracked birds (n = 19 individuals) from a single breeding colony, with evidence for loop migration in all but one of the tracked swallows. In general, two migratory strategies were distinguished. In the first, birds wintering in a belt stretching from southcentral to southern Africa that used an eastern route for both the spring and autumn migration, then shifted their spring migration eastwards (anti‐clockwise loops, n = 12). In the second, birds used an eastern or central route to their wintering grounds in central Africa, shifting the spring migration route westward (clockwise loops, n = 7). In addition, we observed an extremely wide clockwise loop migration encompassing the entire Mediterranean, with one individual utilising both the eastern (autumn) and western (spring) migratory flyway during a single annual migration cycle. Further investigation is needed to ascertain whether clockwise migratory loops encircling the entire Mediterranean also occur other small long‐distance passerine species.

Detours in long-distance migration across the Qinghai-Tibetan Plateau: individual consistency and habitat associations.

Migratory birds often follow detours when confronted with ecological barriers, and understanding the extent and the underlying drivers of such detours can provide important insights into the associated cost to the annual energy budget and the migration strategies. The Qinghai-Tibetan Plateau is the most daunting geographical barrier for migratory birds because the partial pressure of oxygen is dramatically reduced and flight costs greatly increase. We analyzed the repeated migration detours and habitat associations of four Pallas’s Gulls Larus ichthyaetus across the Qinghai-Tibetan Plateau over 22 migration seasons. Gulls exhibited notable detours, with the maximum distance being more than double that of the expected shortest route, that extended rather than reduced the passage across the plateau. The extent of longitudinal detours significantly increased with latitude, and detours were longer in autumn than in spring. Compared with the expected shortest routes, proximity to water bodies increased along autumn migration routes, but detour-habitat associations were weak along spring migration routes. Thus, habitat availability was likely one, but not the only, factor shaping the extent of detours, and migration routes were determined by different mechanisms between seasons. Significant between-individual variation but high individual consistency in migration timing and routes were revealed in both seasons, indicating a stronger influence of endogenous schedules than local environmental conditions. Gulls may benefit from repeated use of familiar routes and stopover sites, which may be particularly significant in the challenging environment of the Qinghai-Tibetan Plateau.

Honey buzzards don't always make a beeline.

(a) European honey buzzards breeding in Western Europe primarily use soaring flight to make annual long-range migrations via the Strait of Gibraltar to winter in West Africa; this adult male was photographed on migration near Gibraltar. Photo: Javier Elloriaga. (b) Autumn migration routes of 12 satellite tagged adult European honey buzzards (colour-coded lines); compared with the shortest possible straight-line routes (dashed lines), most routes involved substantial westerly detours in Africa. Adapted from Vansteelant etal. (2016). (c) In contrast, Montagu's harriers predominantly use flapping flight during their migrations; this adult male is carrying a satellite transmitter. Photo: Theo van Kooten. (d) Autumn migration routes of 34 satellite tagged adult Montagu's harriers; migratory tracks more closely approached straight-line routes, and typically involved longer sea crossings, than seen in European honey buzzards. Adapted from Trierweiler etal. (). In Focus: Vansteelant, W.M.G., Shamoun-Baranes, J., van Manen, W., van Diermen, J. & Bouten, W. (2017) Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway. Journal of Animal Ecology, 86, 179-191. Migratory birds often make substantial detours from the shortest possible route during their annual migrations, which may potentially increase the duration and energetic cost of their journeys. Vansteelant etal. () investigate repeated migrations of adult European honey buzzards between the Netherlands and sub-Saharan Africa, and find that they make large westerly detours in Africa on both the spring and autumn routes. These detours allow migrants to capitalise on more favourable winds further along the route, thus reducing energy expenditure. Lifelong tracking studies will allow researchers to identify how migration routes have evolved to exploit predictable atmospheric and oceanic circulation patterns.

Year-round spatiotemporal distribution of the enigmatic Semi-collared Flycatcher Ficedula semitorquata

We examined migration routes and non-breeding sites of a poorly studied long-distance migrant, the Semi-collared Flycatcher Ficedula semitorquata, by tracking adult birds with geolocators from an eastern European breeding population across two subsequent years. All 11 birds migrated in a clockwise loop fashion where autumn migration routes lay east from the spring migration routes. Non-breeding sites were located in Eastern-Central Africa, i.e. Uganda, Tanzania, Burundi, Rwanda, and east DR Congo, where birds spent on average 128 days. Non-breeding sites of two birds were located outside of the currently estimated species’ non-breeding range.

Microglia and neurons in the hippocampus of migratory sandpipers.

The semipalmated sandpiper Calidris pusilla and the spotted sandpiper Actitis macularia are long- and short-distance migrants, respectively. C. pusilla breeds in the sub-arctic and mid-arctic tundra of Canada and Alaska and winters on the north and east coasts of South America. A. macularia breeds in a broad distribution across most of North America from the treeline to the southern United States. It winters in the southern United States, and Central and South America. The autumn migration route of C. pusilla includes a non-stop flight over the Atlantic Ocean, whereas autumn route of A. macularia is largely over land. Because of this difference in their migratory paths and the visuo-spatial recognition tasks involved, we hypothesized that hippocampal volume and neuronal and glial numbers would differ between these two species. A. macularia did not differ from C. pusilla in the total number of hippocampal neurons, but the species had a larger hippocampal formation and more hippocampal microglia. It remains to be investigated whether these differences indicate interspecies differences or neural specializations associated with different strategies of orientation and navigation.

Satellite Telemetry of the Annual Migration of Baikal TealAnas formosaWintering at Katano-Kamoike, Ishikawa, Japan

Baikal Teal were tracked, by satellite telemetry, in order to identify their migration route between their wintering grounds at Katano-kamoike, Ishikawa, Japan and their breeding range in Russia, and to identify the staging sites they use during migration. In the winter of 2012, four Baikal Teal were captured and satellite transmitters were attached to each individual. From 2012 to 2013, we tracked two of the four teal throughout their annual migration. In the spring, they crossed the Sea of Japan in late March and used stopovers in the Khanka Plain and the Three Rivers Plain for about one month. In early June, they reached their Arctic summer sites in the estuaries of the Indigirka and Khroma rivers of the Sakha Republic, Russia. They remained there for about three months and commenced their autumn migration in early September. The autumn migration route as far as the Three Rivers Plain was similar to that in spring, but after leaving the Three Rivers Plain, they moved to the western part of South Korea and stayed at Seomjin River and other rivers for several weeks. Finally, one of them returned to Katano-kamoike in January and spent more than two months of the winter there. In this study, we identified a total of 19 wetlands as important sites for Baikal Teal; three wintering sites, 13 stopover sites, one stopover/wintering site and two summer sites.

Distribution and movements of Alaska-breeding Steller's Eiders in the nonbreeding period

ABSTRACT Steller's Eiders (Polysticta stelleri) that breed in Alaska, USA, are listed as threatened under the U.S. Endangered Species Act (ESA), yet the degree to which these individuals segregate during the nonbreeding period from conspecifics that nest in Russia is unknown. Likewise, very little is known about the timing of use and distribution of autumn migration routes, stopover sites, and molting and wintering areas by the Alaska-breeding population. To address this information need, we implanted 14 Steller's Eiders with satellite transmitters in 2000 and 2001 at their primary Alaskan breeding grounds near Barrow. We found no evidence for segregation of the Alaska-breeding population in midwinter because locations were well-distributed along the Alaska Peninsula, congruent with prevailing knowledge about the wintering distribution of Steller's Eiders that breed in Russia. During the wing molt, from late August to early October, 7 of 13 individuals used Kuskokwim Shoals, corroborating the importance o...

Trans-Gulf of Mexico loop migration of tree swallows revealed by solar geolocation

Abstract One of the greatest feats of avian migration is the non-stop crossing of extensive areas of inhospitable habitat such as deserts and seas. Differences in spring and autumn migration routes have been reported in species that cross such barriers, and are thought to have evolved in response to seasonal variation in prevailing wind direction. We tested the hypothesis that migration routes vary seasonally with respect to the Gulf of Mexico in the tree swallow Tachycineta bicolor using solar geolocators attached and retrieved at 4 breeding sites in central North America. We found that 100 % of birds (n = 10) made a trans-Gulf flight of >850 km from Louisiana south to their wintering grounds in the Yucatan Peninsula in 12–36 hours, achieving minimum ground speeds as high as 32 m/s. Although most days during autumn migration were characterized by unfavorable headwinds blowing to the northwest, migration over the Gulf mostly occurred on days with strong winds blowing to the south. In contrast, in 8 of 9 (88 %) birds on spring migration returned from the wintering grounds towards Louisiana following a clockwise loop pat tern flying over land to the west around the Gulf. During this spring period there were few days with prevailing winds from the south to assist northward migration. Results suggest that, despite being up to three times further (ca. 2,700 km), a coastal cir- cum-Gulf spring migration represents the less risky route when wind conditions are not favorable. These findings also help to re solve a long-standing dispute in the literature concerning migration patterns between the US Gulf coast and Mexico, and provide insight into the factors shaping migration strategies of small songbirds migrating across large bodies of water.

First indications of autumn migration routes and destination of common minke whales tracked by satellite in the North Atlantic during 2001–2011

First indications of autumn migration routes and destination of common minke whales tracked by satellite in the North Atlantic during 2001–2011