While advances in biologging have revealed many spectacular animal migrations, it remains poorly understood how young animals learn to migrate. Even in social species, it is unclear how migratory skills are transmitted from one generation to another and what implications this may have. Here we show that in Caspian terns Hydroprogne caspia family groups, genetic and foster male parents carry the main responsibility for migrating with young. During migration, young birds stayed close to an adult at all times, with the bond dissipating on the wintering grounds. Solo-migrating adults migrated faster than did adults accompanying young. Four young that lost contact with their parent at an early stage of migration all died. During their first solo migration, subadult terns remained faithful to routes they took with their parents as young. Our results provide evidence for cultural inheritance of migration knowledge in a long-distance bird migrant and show that sex-biased (allo)parental care en route shapes migration through social learning.

Generalist predators may vary their diet and use of habitat according to both internal state (e.g. breeding stage) and external (e.g. weather) factors. Lesser black-backed gulls Larus fuscus (Linnaeus 1758) are dietary generalists, foraging in both terrestrial and marine habitats during breeding. We investigate what affects the gulls’ propensity to forage at sea or on land. We assess the importance of terrestrial foraging to gulls in the Baltic Sea (sub. sp. L. f. fuscus), looking especially at their use of agricultural fields. Through the GPS tracking of 19 individuals across 3 years we tracked 1038 foraging trips and found that 21.2 % of foraging trips were predominantly terrestrial, 9.0 % were a mix of terrestrial and marine, and 68.5 % were exclusively marine. Terrestrial trips were (1) more frequent when departing around sunrise, whereas marine trips occurred throughout the day. Additionally, trips with mostly land-based foraging decreased as the breeding season progressed, suggesting dietary switching coincident with the onset of chick provisioning. (2) During cloudy and cold conditions terrestrial foraging trips were more likely. (3) We found no differences between sexes in their land-based foraging strategy. (4) Gull individuals showed great variation in foraging strategy. Using observations of agricultural fields, carried out for one year, we found that (5) gulls preferentially foraged on fields with short vegetation, and there was a positive association with occurrence of waders and other species of gulls. (6) The availability and use of these preferred fields decreased through the breeding period. This study found high prevalence of terrestrial foraging during early breeding as well as support for dietary switching early in the breeding season. The overall tendency for marine or terrestrial foraging was consistent within individuals, with gull identity accounting for much of the variation observed in foraging trips. Our results suggest that anthropogenic terrestrial food sources may play a role in the low breeding success of these gulls through either variation in quantity and/or quality. Finally, our study demonstrates the potential of combining data from GPS-tracking of individual animals with the ‘ground-truthing’ of habitat visited to elucidate the otherwise nebulous behavior of a generalist predator.

With the rapid expansion of offshore windfarms (OWFs) globally, there is an urgent need to assess and predict effects on marine species, habitats, and ecosystem functioning. Doing so at shelf-wide scale while simultaneously accounting for the concurrent influence of climate change will require dynamic, multitrophic, multiscalar, ecosystem-centric approaches. However, as such studies and the study system itself (shelf seas) are complex, we propose to structure future environmental research according to the investigative cycle framework. This will allow the formulation and testing of specific hypotheses built on ecological theory, thereby streamlining the process, and allowing adaptability in the face of technological advancements (e.g. floating offshore wind) and shifting socio-economic and political climates. We outline a strategy by which to accelerate our understanding of environmental effects of OWF development on shelf seas, which is illustrated throughout by a North Sea case study. Priorities for future studies include ascertaining the extent to which OWFs may change levels of primary production; whether wind energy extraction will have knock-on effects on biophysical ecosystem drivers; whether pelagic fishes mediate changes in top predator distributions over space and time; and how any effects observed at localized levels will scale and interact with climate change and fisheries displacement effects.

Conflicts of interest between resource extraction and conservation are widespread, and negotiating such conflicts, or trade‐offs, is a key issue for ecosystem managers. One such trade‐off is resource competition between fisheries and marine top predators. Managing this trade‐off has so far been difficult due to a lack of knowledge regarding the amount and distribution of prey required by top predators. Here, we develop a framework that can be used to address this gap: a bio‐energetic model linking top predator breeding biology and foraging ecology with forage fish ecology and fisheries management. We apply the framework to a Baltic Sea colony of common guillemots Uria aalge and razorbills Alca torda, two seabird species sensitive to local prey depletion, and show that densities of forage fish (sprat Sprattus sprattus and herring Clupea harengus) corresponding to the current fisheries management target B_MSY are sufficient for successful breeding. A previously proposed fisheries management target for conserving seabirds, 1/3 of historical maximum prey biomass (B_1/3), was also sufficient. However, the results highlight the importance of maintaining sufficient prey densities in the vicinity of the colony, suggesting that fine‐scale spatial fisheries management is necessary to maintain high seabird breeding success. Despite foraging on the same prey, razorbills could breed successfully at lower prey densities than guillemots but needed higher densities for self‐maintenance, emphasizing the importance of considering species‐specific traits when determining sustainable forage fish densities for top predators. Synthesis and applications. Our bio‐energetic modelling framework provides spatially explicit top predator conservation targets that can be readily integrated with current fisheries management. The framework can be combined with existing management approaches such as dynamic ocean management, marine spatial planning and management strategy evaluation to inform ecosystem‐based management of marine resources.

Capsule: Foraging behaviour in the Razorbill Alca torda during breeding was similar to that found elsewhere, aside from dive shape. Aims: To investigate the foraging behaviour of Razorbills during the breeding season at the largest colony in the central Baltic Sea. Methods: A combination of global positioning system (GPS) and time-depth recorder (TDR) devices were used on Razorbills breeding on the island of Stora Karlsö, Baltic Sea, during the chick-rearing period. Results: Five GPS tracks and nine TDR logs were retrieved from 12 Razorbills, and 7399 dives were analysed. Razorbills foraged south and southwest of the colony. Maximum and mean (±sd) foraging range from the colony was 72.7 km and 13.1 ± 13.5 km, respectively. Mean dive depth (15.3 ± 2.4 m) and duration (53.1 ± 8.5 s) were similar to those of a more southern Baltic Sea Razorbill colony. Dive depth had a bimodal distribution, with 70% of dives deeper than 10 m and 30% shallower than 10 m. There was a clear diel foraging pattern with 89% of dives occurring during daytime and a higher proportion of shallow dives at night. Unexpectedly, dives were primarily U-shaped. The Razorbills spent 31% of their overall time activity budget flying or diving. Conclusion: Aside from dive shape, foraging behaviour was consistent with that reported at other colonies of Razorbills. Inconsistency in dive shape may be due to a bimodal foraging strategy, local prey behaviour or competition with the Common Guillemot Uria aalge.