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Capsule: Using ring recovery records collected in Britain and Ireland from 1935 to 2015, we investigated philopatry and dispersal in Black Guillemots Cepphus grylle ringed as nestlings and ...

Capsule: One of the southernmost populations of the Black Guillemot Cepphus grylle is currently endangered, and the risk may be exacerbated by climate change. Aims: We evaluated the future vulnerability of the Black Guillemot by predicting the impact of climate change on the geographic distribution of its breeding and foraging range in the Baltic Sea. Methods: We used MaxEnt, a species distribution modelling technique, to predict the current and future breeding grounds and foraging sites. Results: We found that although the foraging range is expected to increase in the southern Baltic Sea in future, these areas will no longer be suitable as breeding grounds due to a changing climate, creating a spatial mismatch. Conclusion: Our predictions indicate where threats to the species may be most severe and can be used to guide conservation planning. We advocate conservation measures which integrate potential future threats and focus on breeding sites across the current and future potential geographic range of the Black Guillemot.

Capsule Dive behaviour in Black Guillemots Cepphus grylle was close to that predicted for a benthic forager by allometry based on body mass.Aims To report the diving behaviour of Black Guillemots in Northern Ireland.Methods A time-depth-recorders and GPS logger were deployed on four chick-rearing breeding Black Guillemots.Results Dive shape implied most dives were benthic with a small number at the start of each bout associated with searching. Diving only occurred during daylight hours, but dive depth was unrelated to light availability outside of the twilight periods. Dive durations (max = 90 s; mean = 54 s) were shorter and dive depths (max = 15 m; mean = 9 m) were shallower than recorded for guillemots elsewhere. The birds dived a maximum of 1.8 km from the colony.Conclusions Black Guillemots' dive duration was similar to the value predicted from allometry, and is therefore likely representative of this species. Bathymetry likely influences the dive behaviour of this benthic-feeding species because mos...

Surveys of adult Black Guillemots associated with breeding habitat in the pre-breeding period recorded totals of 6883 in Orkney and 12,008 in Shetland. These populations are much larger than was previously thought, largely due to improved census methods and coverage. Although the distribution of suitable sites influenced the distribution of nests, breeding was widespread with most colonies comprising fewer than 20 birds. Nest sites accessible to ground predators were used on islands free from Brown Rats or Stoats but on infested islands Black Guillemots bred only in higher cliffs. The lowest breeding densities were in Yell Sound and it is likely that the population there was still recovering from the effects of a large oil spill.