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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...

Capsule Black Guillemots Cepphus grylle were recorded diving in the Pentland Firth to an average depth of 32 metres and an overall maximal depth of 43 metres. The majority (88%) of dives were benthic with a median dive duration of 95 seconds, and a maximal dive duration of 131 seconds. The results provide empirical evidence that Black Guillemots use depths within the water column at which tidal turbines are likely to operate. Although limited, our data suggest the potential for interactions between Black Guillemots and marine renewable energy devices.

The progression of pre-breeding moult in adult Black Guillemots Cepphus grylle was observed at Bangor, Co. Down. Moult began as soon as early November, which is much earlier than more northerly populations in the UK. Moult was completed within ten weeks. Early return to the breeding colony and early moult may help individuals to obtain breeding sites.

The orientation of fish in the bill of Black Guillemots feeding young was studied in 1983–84 at a Shetland colony. Observations of marked birds revealed that only 20% of individuals exhibited a significant orientation preference, and that few showed strong preferences. Only one bird showed a consistent significant preference in both years. It is suggested that regular use of specific foraging sites may be an important factor in explaining apparent handedness, since adults might try to minimize the drag caused by long, flapping fish by holding the head pointing into wind.

The diurnal rhythm of colony attendance by Black Guillemots varied seasonally. No tidal effects were detected but in April attendance was lower when winds exceeded force 4. Numbers were most stable during 05.00–08.00 GMT in the pre-breeding period. Counts at this time and in winds of force 4 or less provide the best estimate of adult populations. Between late March and mid-May, counts of adults associated with breeding habitat account for most birds occupying suitable nest sites and censuses in northern Britain should be conducted in this period. As the proportion of non-breeding adults varies between colonies, no universal correction factor can be used to estimate the number of breeding attempts from counts of birds. Counts aimed at detecting maximum attendance provide greater accuracy than single counts made by flushing all birds on to the sea but take longer. Monitoring units should be stretches o-f coastline that include a number of colonies of different sizes.

The sequence and timing of moult in Shetland was similar to that found for the same subspecies in western Scandinavia. Winter sea surface temperature is similar in these areas and is probably a key factor affecting the timing of the spring body moult. Immatures began the spring moult later than, and the full autumn moult earlier than adults. Adults are flightless for 4–5 weeks, mostly during September, when they congregate in moult flocks.

Greatly increased ringing effort in recent years now permits a detailed analysis of Black Guillemot recoveries. The cause of death was unknown for 76% of recoveries, and human‐induced mortality factors accounted for relatively few deaths compared with the situation in Scandinavian countries. Oil pollution and marine salmon farming are underestimated as mortality factors by this anlaysis. There are distinct regional differences in the extent of movements: birds from the main groups of Orkney and Shetland islands rarely move outside the archipelago, whereas those ringed on the isolated islands of Foula and Fair Isle often move considerable distances in search of suitable sheltered feeding areas outside the breeding season. Therefore, ringing recoveries from isolated, exposed islands should not be taken as representative of the British and Irish population of this species.

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.