For migratory seabirds, staging and wintering areas may be important targets for conservation. Declines of Roseate Tern Sterna dougallii populations have led to conservation initiatives at breeding sites on both sides of the North Atlantic. However, these could be compromised by environmental conditions in non‐breeding areas. The migratory ecology of Roseate Terns is poorly known and we used light‐level biologgers (geolocators) to identify the migratory routes, staging and wintering areas of Roseate Terns from two European colonies. Most birds wintered off the Ghanaian coast in the Gulf of Guinea, but some wintered further west off Sierra Leone and Liberia, or changed locations during the winter. In these areas, cold‐water upwellings of the Guinea Current Large Marine Ecosystem (GCLME) may provide vital foraging resources. Geolocations in combination with temperature measurements and satellite sea‐surface temperature data show that cold‐water upwellings of the Canary Current Large Marine Ecosystem (CCLME) were important areas for migratory staging, particularly on the return migration which was slower than the outward journey. These results emphasize the importance of productive cold‐water upwellings in the migratory ecology of Roseate Terns. The GCLME and CCLME are under threat from over‐exploitation, pollution and climate change; effective conservation of these environments will be important to secure the long‐term future of these and other seabirds.
Albatrosses and other seabirds are generally highly philopatric, returning to natal colonies when they achieve breeding age. This is not universal, however, and cases of extraordinary vagrancy are rare. The Tristan Albatross (Diomedea dabbenena) breeds on Gough Island in the South Atlantic Ocean, with a small population on Inaccessible Island, Tristan da Cunha, ca 380 km away. In 2015, we observed an adult male albatross in Gonydale, Gough Island, which had been ringed on Ile de la Possession, Crozet Islands in 2009 when it was assumed to be an immature Wandering Albatross (D. exulans). We sequenced 1109 bp of the cytochrome b mitochondrial gene from this bird, and confirmed it to be a Tristan Albatross, meaning its presence on Crozet 6 years previous, and nearly 5000 km away, was a case of prospecting behaviour in a heterospecific colony. Given the challenges in identifying immature Diomedea albatrosses, such dispersal events may be more common than thought previously.
The provision of artificial nest structures is used in the conservation of a broad range of bird groups including raptors, owls, ducks, passerines and seabirds, with varying degrees of success.
Artificial nestboxes have been provided to increase the density and breeding success of Roseate Tern pairs at colonies in north‐west Europe and the eastern seaboard of the USA and Canada, but their effect on breeding productivity has never been comprehensively quantified.
Using 15 years of monitoring data, based on daily nest monitoring visits, we carried out a comparative analysis of the breeding performance of Roseate Tern pairs utilizing artificial nestboxes with those in open nests, on Rockabill Island (Ireland), to evaluate the effectiveness of nestbox installation as a conservation measure.
Nestboxes were used ahead of open sites early in the season, likely by the experienced breeding pairs. Hatching success and fledging success were higher for pairs in nestboxes compared with those in open nest sites. Earlier clutches were more successful than later ones, independent of the effects of nest site type.
The results of this study show definitively that Roseate Terns nesting in nestboxes perform better than those using open nest sites at their largest European colony and that nestboxes are chosen ahead of other sites, likely by the experienced breeding pairs. We recommend the continued and expanded use of nestboxes to help maximize the densities and breeding performance of the Roseate Tern.
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