Brunnich's Guillemot Uria Research Articles

Time allocation and foraging behaviour of chick‐rearing Brünnich's Guillemots Uria lomvia in high‐arctic Greenland

Data-loggers were used to measure the flight and diving activity of Brunnich's Guillemots Uria lomvia breeding in a colony in the North Water polynya. During a total of 51.1 bird-days the birds spent an average of 16.6% (4.0 h/day) of their time underwater, 7.1% in flight (1.7 h/day), 25.4% surface swimming and 50.9% on nest attendance. At-sea time budget included time spent commuting through the water column (8.0% of total time) bottom time available for chasing prey (8.6%), interdive breaks on the surface (9.9%) and long breaks between diving bouts (15.6%). Mean dive duration was 122.9 (± 45.4 sd) s (maximum 240 s). Median dive depth was 48.9 m, but birds showed highly individual depth preferences. Mean foraging trip duration was 8.9 ± 1.3 h, but differed significantly between individuals (range 1.37-20.4 h). The number of dives performed during a trip increased with trip duration, as did total time spent flying, suggesting long trips were used to reach distant foraging grounds and the whole trip was used for active foraging. The birds spent an average of 1.3 ± 0.8 h/day in flight, and estimated potential foraging range averages 42 ± 25.9 km; 67% of all trips could not have exceeded 50 km. Trip start and dive initiation were bimodally distributed with peaks morning and evening despite continuous daylight in the study area. Compared to studies of time allocation and trip duration in Common Guillemot populations, the high-arctic Brunnich's Guillemots seemed to work harder during the breeding season, and to have few options for further increasing foraging effort.

Predation by RavensCorvus coraxon Brunnich's GuillemotUria lomviaeggs and chicks and its possible impact on breeding site selection

We studied the behaviour of RavensCorvus coraxtaking the eggs or chicks of Brunnich's GuillemotsUria lomviaat East Digges Island, Northwest Territories, Canada. We classified the characteristics of the breeding sites attacked by Ravens according to their location on the cliffs, the width of the breeding ledge, the number of adjacent rock faces and the density of nearby breeding guillemots. Ravens selectively attacked peripheral sites near the top of the occupied area, those on narrow ledges and those with few close neighbours. The risk of predation at the most vulnerable sites was more than seven times the average. For the most part, breeding success at 419 sites near the cliff top conformed to predictions based on the observations of Raven predation. However, losses observed over 3 years suggested that more eggs fall accidentally than are taken by avian predators. We concluded that the risks of predation and of accidental dislodgement both contribute to choice of nest sites by Brunnich's Guillemots. The effect of multiple close neighbours in deterring predation by Ravens may be important in determining the density of guillemot breeding sites within the colony.

Small oil spill kills 10–20 000 seabirds in North Norway

An estimated 10–20 000 seabirds were killed by a very small oil spill off the coast of North Norway in March 1979. Despite the fact that over 90% of these were Brunnich's Guillemots Uria lomvia, the breeding population of this species was not considered to have been seriously threatened by this spill. On the other hand, this episode did illustrate how extremely vulnerable certain seabird species are to oil.