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Tiny tern takes flight
Tiny Tern's journey begins! Arctic terns make the longest migration of any species. Every year, they fly from the northern Arctic to the southern Antarctic--and back--spending most of the year in flight. As the days grow shorter and colder, Tiny Tern and his flock prepare to leave the Arctic and begin their journey towards sunlight and warmth. The terns travel all the way to the other side of the world. Along the way, they encounter many dangers. Experience a bird's-eye view of getting lost in heavy storms, protecting hatchlings from predators, and finally reaching your destination. Following the story, discover more educational content about arctic terns. Read about what they eat, how they fly, and everything they encounter during their time in the Arctic and Antarctic.
CHILDBOOK
Arctic terns from circumpolar breeding colonies share common migratory routes
The Arctic tern is an iconic seabird, famous for its annual migrations between the Arctic and the Antarctic. Its wide geographical range has impeded knowledge of potential population bottlenecks during its annual bi-hemispheric movements. Although Arctic terns breed in the Pacific, Atlantic, and Arctic coasts of North America, few tracking studies have been conducted on North American Arctic terns, and none in Canada, which represents a significant proportion of their circumpolar breeding range. Using light-level geolocators, we tracked 53 Arctic terns from 5 breeding colonies across a wide latitudinal and longitudinal range within North America. We compared the routes taken by birds in our study and migration timing to those previously tracked from Greenland, Iceland, The Netherlands, Sweden, Norway, Maine (USA), and S. Alaska (USA). Most Arctic terns tracked globally used one of 3 southbound migration routes: (1) Atlantic West Africa; (2) Atlantic Brazil; and (3) Pacific coastal, and one of 2 northbound migration routes: (1) Mid-ocean Atlantic and (2) Mid-ocean Pacific. Some other trans-equatorial seabirds also used these migration routes, suggesting that Arctic tern routes may be important for other species. The migration timing for southbound and northbound migrations was generally different between tracked tern colonies worldwide but generally fell within a 1–2 mo window. Our research suggests that conservation management of Arctic terns during their migration should dynamically adapt with the times of the year that terns use parts of their route. Future identification of common multi-species seabird flyways could aid the international negotiations required to conserve pelagic seabirds such as Arctic terns.
Journal Article
Variation in migration behaviors used by Arctic Terns (Sterna paradisaea) breeding across a wide latitudinal gradient
Arctic Terns (Sterna paradisaea) share a few routes to undertake the longest annual migrations of any organism. To understand how the wide spatial range of their breeding colonies may affect their migration strategies (e.g., departure date), we tracked 53 terns from five North American colonies distributed across 30° of latitude and 90° of longitude. While birds from all colonies arrived in Antarctic waters at a similar time, terns nesting in the Arctic colonies migrated back north more slowly and arrived to their breeding grounds later than those nesting in the colony farther south. Arrival dates in Antarctic waters coincided with the start of favorable foraging conditions (i.e., increased ocean productivity), and similarly arrival dates at breeding colonies coincided with the start of local favorable breeding conditions (i.e., disappearance of snow and ice). Larger birds followed a more direct southbound migration route than smaller birds. On both southbound and northbound migrations, daily distances traveled declined as time spent in contact with the ocean increased, suggesting a trade-off between resting/foraging and traveling. There was more unexplained variation in behavior among individuals than among colonies, and one individual had a distinctive stop around Brazil. Terns nesting in the Arctic have a narrow time window for breeding that will likely increase with continuing declines in sea ice and snow. Departing Arctic Terns likely have few clues about the environmental conditions they will encounter on arrival, and their response to environmental changes at both poles may be assisted by large individual variation in migration strategy.
Journal Article
Inuit knowledge of Arctic Terns (Sterna paradisaea) and perspectives on declining abundance in southeastern Hudson Bay, Canada
The Arctic Tern ( Sterna paradisaea ; takatakiaq in Inuttitut) breeds in the circumpolar Arctic and undertakes the longest known annual migration. In recent decades, Arctic Tern populations have been declining in some parts of their range, and this has been a cause of concern for both wildlife managers and Indigenous harvesters. However, limited scientific information is available on Arctic Tern abundance and distribution, especially within its breeding range in remote areas of the circumpolar Arctic. Knowledge held by Inuit harvesters engaged in Arctic Tern egg picking can shed light on the ecology, regional abundance and distribution of this marine bird. We conducted individual interviews and a workshop involving 12 Inuit harvesters and elders from Kuujjuaraapik, Nunavik (northern Québec), Canada, to gather their knowledge of Arctic Tern cultural importance, ecology, and stewardship. Interview contributors reported a regional decline in Arctic Tern numbers which appeared in the early 2000s on nesting islands near Kuujjuaraapik. Six possible factors were identified: (1) local harvest through egg picking; (2) nest disturbance and predation; (3) abandonment of tern nesting areas (i.e., islands that have become connected to the mainland due to isostatic rebound); (4) climate change; (5) natural abundance cycles within the Arctic Tern population; and (6) decline of the capelin ( Mallotus villosus ) in the region. Recommendations from Inuit contributors related to Arctic Tern stewardship and protection included: (1) conduct more research; (2) let nature take its course; (3) conduct an awareness campaign; (4) implement an egg picking ban; (5) coordinate local egg harvest; (6) start ‘tern farming’; (7) protect Arctic Terns across their migration route; and (8) harvest foxes predating on terns. Our study highlighted complementarities between Inuit knowledge and ecological science, and showed that Inuit harvesters can make substantial contributions to ongoing and future Arctic tern research and management initiatives.
Journal Article
Seasonally specific responses to wind patterns and ocean productivity facilitate the longest animal migration on Earth
Migratory strategies of animals are broadly defined by species’ eco-evolutionary dynamics, while behavioural plasticity according to the immediate environmental conditions en route is crucial for energy efficiency and survival. The Arctic tern Sterna paradisaea is known for its remarkable migration capacity, as it performs the longest migration known by any animal. Yet, little is known about the ecology of this record-breaking journey. Here, we tested how individual migration strategies of Arctic terns are adapted to wind conditions and fuelling opportunities along the way. To this end, we deployed geolocators on adult birds at their breeding sites in Svalbard, Norway. Our results confirm fundamental predictions of optimal migration theory: Arctic terns tailor their migration routes to profit from (1) tailwind support during the movement phase and (2) food-rich ocean areas during the stopover phase. We also found evidence for seasonally distinct migration strategies: terns prioritize fuelling in areas of high ocean productivity during the southbound autumn migration and rapid movement relying on strong tailwind support during the northbound spring migration. Travel speed in spring was 1.5 times higher compared to autumn, corresponding to an increase in experienced wind support. Furthermore, with their pole-to-pole migration, Arctic terns experience approximately 80% of all annual daylight on Earth (the most by any animal), easing their strictly diurnal foraging behaviour. However, our results indicate that during migration daylight duration is not a limiting factor. These findings provide strong evidence for the importance of interaction between migrants and the environment in facilitating the longest animal migration on Earth.
Journal Article
Inuit knowledge of Arctic Terns
The Arctic Tern (Sterna paradisaea; takatakiaq in Inuttitut) breeds in the circumpolar Arctic and undertakes the longest known annual migration. In recent decades, Arctic Tern populations have been declining in some parts of their range, and this has been a cause of concern for both wildlife managers and Indigenous harvesters. However, limited scientific information is available on Arctic Tern abundance and distribution, especially within its breeding range in remote areas of the circumpolar Arctic. Knowledge held by Inuit harvesters engaged in Arctic Tern egg picking can shed light on the ecology, regional abundance and distribution of this marine bird. We conducted individual interviews and a workshop involving 12 Inuit harvesters and elders from Kuujjuaraapik, Nunavik (northern Québec), Canada, to gather their knowledge of Arctic Tern cultural importance, ecology, and stewardship. Interview contributors reported a regional decline in Arctic Tern numbers which appeared in the early 2000s on nesting islands near Kuujjuaraapik. Six possible factors were identified: (1) local harvest through egg picking; (2) nest disturbance and predation; (3) abandonment of tern nesting areas (i.e., islands that have become connected to the mainland due to isostatic rebound); (4) climate change; (5) natural abundance cycles within the Arctic Tern population; and (6) decline of the capelin (Mallotus villosus) in the region. Recommendations from Inuit contributors related to Arctic Tern stewardship and protection included: (1) conduct more research; (2) let nature take its course; (3) conduct an awareness campaign; (4) implement an egg picking ban; (5) coordinate local egg harvest; (6) start 'tern farming'; (7) protect Arctic Terns across their migration route; and (8) harvest foxes predating on terns. Our study highlighted complementarities between Inuit knowledge and ecological science, and showed that Inuit harvesters can make substantial contributions to ongoing and future Arctic tern research and management initiatives.
Journal Article
Nest‐site fidelity of Arctic terns Sterna paradisaea in a managed environment exposed to benign human activity
Human activity near seabird colonies is often equated with disturbance. Coping with human disturbance is a critical task in the management of seabird colonies where human access is an issue. Nest‐site fidelity and breeding dispersal were characterised in an Arctic tern population exposed to a high level of benign human activity from resident conservation staff and public visitors. The annual return rate of nesting birds was 90% over the 10‐year study period. Nest‐site fidelity was high with most birds returning to the same 2 × 2 m square in subsequent years, in particular to nest sites that were against walls and exposed to a high level of human activity at close range. This indicates that human activity was not a deterrent to nesting by Arctic terns. Breeding dispersal to other nearby colonies was low, except when related to colony abandonment. The data suggest that benign human activity from resident staff and public visitors can be a positive benefit, both within and across years, to Arctic tern colonies. Managed public access could be considered an effective management tool for Arctic tern conservation, as well as seabird colonies more widely.
Journal Article
Trophic position influences the efficacy of seabirds as metal biovectors
Seabirds represent a well documented biological transport pathway of nutrients from the ocean to the land by nesting in colonies and providing organic subsidies (feces, carcasses, dropped food) to these sites. We investigated whether seabirds that feed at different trophic levels vary in their potency as biovectors of metals, which can bioaccumulate through the marine foodweb. Our study site, located on a small island in Arctic Canada, contains the unique scenario of two nearby ponds, one of which receives inputs almost exclusively from upper trophic level piscivores (Arctic terns, Sterna paradisaea) and the other mainly from lower trophic level molluscivores (common eiders, Somateria mollissima). We used dated sediment cores to compare differences in diatoms, metal concentrations and also stable isotopes of nitrogen (δ¹⁵N), which reflect trophic position. We show that the seabirds carry species-specific mixtures of metals that are ultimately shunted to their nesting sites. For example, sediments from the tern-affected pond recorded the highest levels of δ¹⁵N and the greatest concentrations of metals that are known to bioaccumulate, including Hg and Cd. In contrast, the core from the eider-affected site registered lower δ¹⁵N values, but higher concentrations of Pb, Al, and Mn. These metals have been recorded at their greatest concentrations in eiders relative to other seabirds, including Arctic terns. These data indicate that metals may be used to track seabird population dynamics, and that some metal tracers may even be species-specific. The predominance of large seabird colonies on every continent suggests that similar processes are operating along coastlines worldwide.
Journal Article
The Arctic tern Sterna paradisaea
Elucidating the ecological factors underpinning migratory strategies of seabirds is necessary for understanding resilience to environmental change. Arctic terns Sterna paradisaea breed in the Northern Hemisphere and are unique for the global scale of their migration. Geolocator data from 37 Arctic terns breeding in a low-latitude colony, 10 of which were re-tagged in successive years, were analysed to characterise their migratory behaviour and to test the hypothesis that individuals have repeatable migration strategies. Seawater immersion data suggested a fly−forage strategy, with birds remaining on the wing at night and only foraging during daylight. Southward movement was focused initially along Atlantic eastern-boundary upwelling systems. Most terns then reoriented eastwards, crossing the southern Indian Ocean before moving south to the Antarctic. Foraging intensity differed between migration phases. Indian Ocean foraging locations were diverse, and less frequent over deep ocean basins. Foraging intensity was highest in the later stages of return migration, particularly in and around the Azores Confluence Zone. High movement speeds and foraging intensity on return migration may be adaptations to optimise reproductive success. Some aspects of migration phenology were repeatable between years, but trajectories were displaced by wind. Repeat birds did not use the same foraging areas in different years, and their trajectories across the Indian Ocean also differed. The results of this study suggest that the Indian Ocean crossing is a behaviour pattern, surviving since the last ice age, enabling Arctic terns breeding at low-latitude northwest European colonies to arrive at fragmenting Antarctic sea ice when foraging conditions are suitable.
Journal Article
Foraging Behaviours of Breeding Arctic Terns Sterna paradisaea and the Impact of Local Weather and Fisheries
During the breeding season, seabirds are central place foragers and in order to successfully rear chicks they must adjust their foraging behaviours to compensate for extrinsic factors. When foraging, arctic terns Sterna paradisaea are restricted to the first 50 cm of the water column and can only carry a few prey items back to their nests at once. In Iceland, where 20–30% of the global population breed, poor fledging success has been linked to low food availability. Using GPS loggers, we investigated individual foraging behaviours of breeding adults during incubation from a large colony over four seasons. First, we tested whether foraging trip distance or duration was linked to morphology or sex. Second, we examined how trips vary with weather and overlap with commercial fisheries. Our findings reveal that arctic terns travel far greater distances during foraging trips than previously recorded (approximately 7.3 times further), and they forage around the clock. There was inter-annual variability in the foraging locations that birds used, but no relationship between size or sex differences and the distances travelled. We detected no relationship between arctic tern foraging flights and local prevailing winds, and tern heading and speed were unrelated to local wind patterns. We identified key arctic tern foraging areas and found little spatial or temporal overlap with fishing pelagic vessels, but larger home ranges corresponded with years with lower net primary productivity levels. This suggests that whilst changing polar weather conditions may not pose a threat to arctic terns at present, nor might local competition with commercial fisheries for prey, they may be failing to forage in productive areas, or may be affected by synergistic climatic effects on prey abundance and quality. Shifts in pelagic prey distributions as a result of increasing water temperatures and salinities will impact marine top predators in this region, so continued monitoring of sentinel species such as arctic terns is vital.
Journal Article