Common Guillemot Uria Aalge Research Articles

Monitoring the Atlantic Puffin Fratercula arctica, Common Guillemot Uria aalge and Black-legged Kittiwake Rissa tridactyla breeding populations on Hornøya, northeast Norway, 1980-2000

The breeding populations of Atlantic Puffins Fratercula arctica, Common Guillemots Uria aalge and Black-legged Kittiwakes Rissa tridactyla have been monitored on Hornøya, East Finnmark since 1980 as part of the Norwegian seabird monitoring programme. Whereas numbers of Puffin burrows in plots monitored in 1981 - 1993 increased at a rate of 2.6% per year, there was no subsequent trend in counts made in a new scheme of circular plots started in 1990. Numbers of Common Guillemots collapsed between 1985 - 1987 but have since increased in all plots at a rate of 11.6% per year. Kittiwake numbers dropped significantly (1.5% per year) between 1980 - 1994, but stabilised between 1994 - 2000. Suggestions are made for improvements to the monitoring scheme to overcome inconsistencies in changes in numbers between plots (e.g. of Kittiwakes), to increase the sensitivity of the counts and for additions to help explain why any changes in the populations occur.

The rise and fall of cliff-breeding seabirds in Sør-Varanger, NE Norway, 1970-2002

Surveys of seabirds breeding along the coast of Sør-Varanger, NE Norway were carried out in 1989, 1996, 1999 and 2002 as a continuation of a monitoring study started in 1970. Until 1983, by which time 47 colonies were occupied, there had been a rapid increase in numbers of Black-legged Kittiwakes Rissa tridactyla and European Shags Phalacrocorax aristotelis breeding in the area while the Great Cormorant P. carbo population had first increased and then declined. Between 1983 and 2002, the Kittiwake and Shag populations declined by ca. 60% and 85% respectively while that of Cormorants first continued to decline and then recovered to levels recorded in the 1970s. The decline in Common Guillemot Uria aalge and Razorbill Alca torda numbers recorded since 1970 culminated in 1989 when no birds were seen in the region. Since then, one individual Common Guillemot was seen in 1999. In 2002 approximately 7500 pairs of Kittiwake, 770 pairs of Cormorant and 15 pairs of Shag bred in 23 colonies. Possible causes for the main population changes are briefly discussed.

Seabird bycatch in European waters

AbstractThe incidental capture (bycatch) of seabirds is a global conservation issue and a top threat to European species that demands urgent conservation and management action. Here, we present the first European review of seabird bycatch data, considering all fishing gears and data collection methods available in the region. We calculate seabird bycatch numbers per species, family, country and European marine region and assess the reliability of the data available. The cumulative bycatch estimate extracted from this review suggests that about 195,000 seabirds (ranging from around 130,000 to 380,000) are bycaught in European waters annually. The most affected seabird species is the Common Guillemot Uria aalge with over 31,000 birds killed per year. The marine region with the highest bycatch estimate is the Northeast Atlantic (over 115,000 seabirds year−1). Gillnet fisheries are responsible for the highest bycatch levels, with over 95,000 seabirds year−1, followed by longline fisheries. The families most affected by bycatch are Anatidae and Alcidae. These numbers are likely an underestimation since we were unable to find bycatch estimates, or to extrapolate estimates from available bycatch data for 12 (out of 34) European coastal states. Our assessment also identified significant data gaps in key areas such as Gran Sol (in the north‐east Atlantic), the central and Eastern Mediterranean and the Black Sea. Combining systematic data collection with immediate implementation of mitigation measures will be crucial to fill in knowledge gaps, reduce current mortality levels and meet international conservation commitments such as those of the European Union and the Convention on Migratory Species.

Assessing the importance of individual‐ and colony‐level variation when using seabird foraging ranges as impact assessment and conservation tools

Knowledge of seabird distributions plays a key role in seabird conservation and sustainable marine management, underpinning efforts to designate protected areas or assess the impact of human developments. Technological advances in animal tracking devices increasingly allow researchers to acquire information on the movement of birds from specific colonies. Nevertheless, most seabird colonies have not been subject to such tracking and another means must be found to assess their likely foraging distribution. Consequently, foraging range data collated and summarized across other tracking studies has often been used to estimate species‐level foraging distances for use within applied settings. However, generic species‐specific foraging ranges must be used with caution because of the amount of variation in seabird foraging behaviour at both the individual and colony levels. Specifically, although current reviews of seabird foraging ranges provide summary estimates of maximum foraging range, they typically do not assess the extent of among‐colony or among‐individual variation around such estimates. To address this, we conducted a variance component analysis of the maximum distance reached from the breeding colony per foraging trip (foraging range) using multi‐colony tracking datasets to estimate the degree of between‐individual, between‐year and between‐colony variation in foraging range in four UK breeding seabirds (Black‐legged Kittiwake Rissa tridactyla, Common Guillemot Uria aalge, Razorbill Alca torda and European Shag Gulosus aristotelis). We also provide updated estimates of typical foraging ranges for each species and quantify the influence of breeding stage and colony size. Overall, between‐colony variation was typically the largest variance component, explaining 20–30% of the observed variation in foraging range across the four species. Individual‐level variation was also relatively large among Shag. In Kittiwake, Guillemot and Shag, but not Razorbill, average foraging ranges were positively associated with colony size. In addition, Kittiwake and Razorbill travelled further during incubation than during chick‐rearing. More generally, our estimates of mean foraging ranges for each species were subject to a high degree of uncertainty, which should be incorporated into impact assessments carried out using such data.

Diet and prey size preference in Razorbills Alca torda breeding at Stora Karlsö, Sweden

The Razorbill Alca torda is one of three auk species breeding in Sweden, often occurring in colonies with Common Guillemot Uria aalge. The largest colony in the Baltic Sea is situated on the island Stora Karlsö west of Gotland. During the chick-rearing phase, Razorbills forage at sea and return to feed the young with single or multiple prey carried sideways in the bill, unlike Common Guillemots that carry a single fish in the middle of the bill. Clupeids, especially sprat Sprattus sprattus, are the main prey of Baltic Sea Razorbills, but studies are scarce. Here, we investigate the diet preference of Razorbills at Stora Karlsö with regard to prey taxonomy and size, analysing photographs and applying morphometric equations. We show that most feeding attempts involved a single clupeid (88% of known fish taxonomy), in most cases likely sprat. The average prey size (115 mm) and prey species was similar to that of Common Guillemots in the same colony. The variation in size was much smaller in the Razorbill diet than the size distribution of clupeids at sea, indicating a strong prey size selectivity. The Razorbills’ high specialisation underlines the importance of maintaining strong populations of clupeids in their foraging area, as these fish are also targeted by industrial fisheries.

Energetic synchrony throughout the non‐breeding season in common guillemots from four colonies

The non‐breeding season presents significant energetic challenges to birds that breed in temperate or polar regions, with clear implications for population dynamics. In seabirds, the environmental conditions at non‐breeding sites drive food availability and the energetic cost of regulatory processes, resulting in variation in diet, behaviour and energetics; however, very few studies have attempted to understand if and how these aspects vary between populations. We investigated whether non‐breeding location influenced diet, behaviour and energetics in the common guillemotUria aalge. We studied guillemots from four UK breeding colonies, two located on the west coast of Scotland and two on the east. We quantified non‐breeding distribution, foraging behaviour and activity budgets of 39 individuals from July to March, using geolocation–immersion loggers and time‐depth recorders, and used feather stable isotope signatures to infer diet during the post‐breeding moult. We calculated energy expenditure and investigated whether the peak (an indicator of the potential vulnerability to marine threats) varied between colonies. Individuals were spatially segregated according to the coastline they breed on, with west coast guillemots distributed off the west coast of the UK and east coast guillemots distributed off the east coast. Diet and behaviour were more similar in guillemots that shared a breeding coastline than those that did not, as west coast guillemots foraged at a lower trophic level, spent less time diving and engaged in more pelagic foraging than east coast guillemots. However, energy expenditure was remarkably similar between colonies, peaking during late February/early March, indicating that, during our study period, there was high synchrony between colonies in the timing of potential vulnerability to marine threats. Therefore, any anthropogenic changes that result in decreased food availability or increased energy expenditure during late winter may have greater impacts on energy balance, with consequences for population dynamics.

Long‐term within‐season changes in the diet of Common Guillemot (Uria aalge) chicks at a North Sea colony: implications for dietary monitoring

Over four decades (1982–2019) there were pronounced within‐season changes in the proportion of a key prey species (Lesser Sandeel Ammodytes marinus) in Common Guillemot Uria aalge chick diet. As Sandeels became scarcer their occurrence was largely confined to the early part of the chick period. Consequently, the mean annual proportion of Sandeels was poorly estimated if sampling occurred within a short time window, particularly if this was early or late in the season. Within‐season variation is rarely considered in diet monitoring but our results highlight the need for further analyses across other species and sites to develop a deeper understanding of how best to optimize sampling protocols.

Effects of competitive pressure and habitat heterogeneity on niche partitioning between Arctic and boreal congeners

The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey but also that of competitors (e.g. southerly species expanding their range into the Arctic). Species can respond to interspecific competition by segregating along different niche axes. Here, we studied spatial, temporal and habitat segregation between two closely related seabird species: common guillemot Uria aalge (a temperate species) and Brünnich’s guillemot Uria lomvia (a true Arctic species), at two sympatric sites in Iceland that differ in their total population sizes and the availability of marine habitats. We deployed GPS and temperature-depth recorders to describe foraging locations and behaviour of incubating and chick-rearing adults. We found similar evidence of spatial segregation at the two sites (i.e. independent of population sizes), although segregation in environmental space was only evident at the site with a strong habitat gradient. Unexpectedly, temporal (and, to a limited extent, vertical) segregation appeared only at the least populated site. Overall, our results show complex relationships between the levels of inferred competition and that of segregation.

Six pelagic seabird species of the North Atlantic engage in a fly-and-forage strategy during their migratory movements

Bird migration is commonly defined as a seasonal movement between breeding and non-breeding grounds. It generally involves relatively straight and directed large-scale movements, with a latitudinal change, and specific daily activity patterns comprising less or no foraging and more traveling time. Our main objective was to describe how this general definition applies to seabirds. We investigated migration characteristics of 6 pelagic seabird species (little auk Alle alle, Atlantic puffin Fratercula arctica, common guillemot Uria aalge, Brünnich’s guillemot U. lomvia, black-legged kittiwake Rissa tridactyla and northern fulmars Fulmarus glacialis). We analysed an extensive geolocator positional and saltwater immersion dataset from 29 colonies in the North-East Atlantic and across several years (2008-2019). We used a novel method to identify active migration periods based on segmentation of time series of track characteristics (latitude, longitude, net-squared displacement). Additionally, we used the saltwater immersion data of geolocators to infer bird activity. We found that the 6 species had, on average, 3 to 4 migration periods and 2 to 3 distinct stationary areas during the non-breeding season. On average, seabirds spent the winter at lower latitudes than their breeding colonies and followed specific migration routes rather than non-directionally dispersing from their colonies. Differences in daily activity patterns were small between migratory and stationary periods, suggesting that all species continued to forage and rest while migrating, engaging in a ‘fly-and-forage’ migratory strategy. We thereby demonstrate the importance of habitats visited during seabird migrations as those that are not just flown over, but which may be important for re-fuelling.

The Great Auk (Pinguinus impennis) had two brood patches, not one: confirmation and implications

Since the late 1600s it has been assumed that the Great AukPinguinus impenniswas similar to the Common GuillemotUria aalgeand Brünnich's GuillemotUria lomviain having a single, central brood patch. Through the examination of eight mounted museum specimens, we show that this is incorrect and that, like its closest relative the RazorbillAlca torda, the Great Auk had two lateral brood patches. We discuss how such misinformation persisted for so long. We also review the relationship between the number of brood patches and clutch size in the Alcidae. One implication of two brood patches is that the Great Auk would have incubated in a horizontal posture like the Razorbill, rather than in a semi‐upright posture like theUriaguillemots. Assuming that the Great Auk incubated like the Razorbill, it would probably have done so horizontally with its single egg pressed against one of the two lateral brood patches, positioned against the inside of one tarsus (and partially on the web of one foot), and with the wing on that side drooped to provide additional protection for the egg. Incubating in this way may have meant that the Great Auk's pyriform egg would have enabled it to use both level and sloping terrain, as in theUriaguillemots (but unlike the Razorbill). A horizontal incubation also has implications for estimates of their breeding density, which we estimate to have been around four pairs per square metre and, hence numbers on its largest known colony, Funk Island, Newfoundland (maximum 250 000 pairs).

Polycyclic aromatic hydrocarbons (PAHs) in seabird eggs in Ireland

Seabird eggs are considered a favourable matrix for monitoring marine pollutants and are widely used as higher trophic level indicators. Concentrations of Polycyclic aromatic hydrocarbons (Σ15PAH) were determined in the eggs of four piscivorous seabirds in Ireland from multiple colonies for the first time, Common Guillemot Uria aalge, Northern Gannet Morus bassanus, Common Tern Sterna hirundo and Arctic Tern S. paradisaea. PAH concentrations were generally lower than levels detected in eggs from other seabird studies and considerably lower than concentrations associated with no adverse effect in the eggs of domestic avian species. This study indicates potential site and species differences in PAH concentrations. Baseline data of PAHs in a range of seabird species from this study may provide an important reference point should a major pollution event occur in European waters, such as an oil spill.

Legacy and emerging contaminants in common guillemot Uria aalge eggs in Ireland and Wales

Guillemot eggs from multiple Irish colonies and one Welsh colony were analysed for legacy pollutants such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and other organochlorine compounds (OCs), as well as metals. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were measured in eggs to understand the influence of diet on contaminant levels detected. Wide-scope target and suspect screening techniques were used on a single guillemot egg, providing novel information on contaminants of emerging concern. Stable isotope ratio analysis showed that guillemots from Great Saltee Island and Lambay Island (Ireland's east coast) had a similar carbon source (δ13C) and fed at similar trophic levels (δ15N), pollutant levels were higher in eggs from Lambay Island near Dublin, Ireland's industrialised capital city. Guillemot eggs from Aughris Head (Atlantic west coast of Ireland), and Skomer Island (Wales) had differing isotopic niches to other colonies. Egg samples from Aughris Head had the lowest levels of pollutants in this study (with the exception of mercury) and amongst the lowest levels reported worldwide. In contrast, Skomer Island had the highest level of pollutants with higher concentrations of Σ16PCB, Σ6PBDE and HCB than Irish colonies, most likely a result of its proximity to historically industrial areas. Levels of PCBs, p,p’ –DDE and mercury in guillemot eggs have decreased over time according to this study, in concurrence with worldwide trends. Levels of pollutants in guillemot eggs, in this study, fall below existing thresholds for adverse effects in other species, with the exception of mercury.

Assessing bycatch risk from gillnet fisheries for three species of diving seabird in the UK

Incidental mortality (bycatch) in fisheries represents a threat to marine vertebrates. Research has predominantly focussed on bycatch in longline fisheries, but bycatch from gillnet fisheries is of increasing concern. To address this concern, we combined comprehensive biologging data sets and multiple sources of fishing effort data to assess the spatial overlap of 3 diving seabird species during the breeding season (common guillemotUria aalge, razorbillAlca tordaand European shagPhalacrocorax aristotelis) with UK gillnet fisheries. Species distribution models based on birds’ diving behaviour identified areas of elevated bycatch risk where high levels of diving activity and fishing effort coincided. In addition, we identified times of day and water depths where diving activity, and hence bycatch risk, may be concentrated. Bycatch risk hotspots for all 3 species were identified along the north-east coast of England. Risk hotspots were also identified along the Pembrokeshire coast for both auk species and along the Cornish coast for shag. Lack of fishing effort data for smaller vessels made it difficult to assess seabird-fishery overlap in Scottish waters. Across species, diving activity was lower at night. For razorbill and guillemot, dive depth tended to increase at sunrise and decrease after sunset. For shag, dive depth showed no diel pattern but was associated with water depth. Our findings should assist in targeting spatio-temporal measures and designing deterrent devices to reduce bycatch. However, scarcity of data on the behaviour of gillnet fishers at comparable spatio-temporal resolution as seabird movement data remains a constraint to fully understanding seabird-fisheries interactions.

МОРСКИЕ КОЛОНИАЛЬНЫЕ ПТИЦЫ ОСТРОВА МЕДНОГО (КОМАНДОРСКИЕ ОСТРОВА)

The results of colonial seabird surveys on Medny Island were presented and the changes in numbers and distribution over the past 20–30 years were analyzed. The number of colonies on the island has not changed. The total number of individuals belonging to19 species is more than 200 thousand pairs. The colonies are distributed on the island relatively evenly along the whole coast and are based on five species – northen fulmar Fulmarus glacialis,black-legged kittiwake Rissa tridactyla, red-legged kittiwake Rissa brevirostris and two species of guillemots. The most numerous species is Northen fulmar. The abundance of the common guillemot Uria aalge has noticeably increased. The glaucous-winged gull Larus glaucescens, the crested auklet Aethia cristatella, the moth horned puffin Fratercula corniculata and the tufted puffin Lunda cirrhata has increased less. The number of parakeet auklet Cyclorrhynchus psittacula has decreased. There was not found significant changes for the rest of species.

Abnormal eggs of the Common Guillemot Uria aalge: the role of stress

This study documents several types of abnormal eggs of the Common Guillemot Uria aalge collected from Bempton Cliffs, Yorkshire, UK, during the 1900s and currently housed in the Natural History Museum at Tring, Hertfordshire, UK. These eggs are abnormal in terms of size, shape, colour and surface topography. We suggest that the incidence of these abnormal eggs was relatively high because the manner in which they were collected — repeated visits to the breeding colony — caused considerable disturbance and stress that in turn disrupted the normal process of egg formation. We discuss the possibility of using abnormalities in avian eggs as a measurement of environmental stress.

Avian egg collections: museum collection bias driven by shape and size

Avian eggs exhibit substantial intra‐ and interspecific variation in shape, size and colour. Considerable efforts have been made to better understand the evolutionary drivers behind such variation, often using museum egg collections. Usually it is assumed that museum collections accurately represent the variation seen in natural populations, but this may not be the case if there is collection bias. Collection bias may lead to the over‐representation of certain egg traits in collections, due to the aesthetic (or other) preferences of collectors. The aim of this study is to begin to look for the occurrence of potential collection bias in museum egg collections by comparing three shape indices (pointedness/asymmetry, elongation and polar asymmetry) and egg volume between subsets of eggs in museum collections with those of recently sampled eggs in the field for three different bird species: common guillemot Uria aalge, razorbill Alca torda and northern fulmar Fulmarus glacialis. We found no evidence of collection bias in our sampled razorbill and northern fulmar museum collection eggs, but some evidence for a bias in sampled museum collection eggs of common guillemots. Since the guillemot's egg differs from most bird eggs in being pyriform, we suggest that collection bias by historic egg collectors may be more prevalent in species with extreme egg traits. Researchers using museum egg collections to examine questions relating to egg shape should be aware of collection bias risks and consider how to minimise the effect of these possible biases on accumulated datasets.

New insights from old eggs – the shape and thickness of Great Auk Pinguinus impennis eggs

We compared the shape and eggshell thickness of Great Auk Pinguinus impennis eggs with those of its closest relatives, the Razorbill Alca torda, Common Guillemot Uria aalge and Brünnich's Guillemot Uria lomvia, in order to gain additional insights into the breeding biology of the extinct Great Auk. The egg of the Great Auk was most similar in shape to that of Brünnich's Guillemot. The absolute thickness of the Great Auk eggshell was greater than that of the Common Guillemot and Razorbill egg, which is as expected given its greater size, but the relative shell thickness at the equator and pointed end (compared with the blunt end) was more similar to that of the Common Guillemot. On the basis of these and other results we suggest that Great Auk incubated in an upright posture in open habitat with little or no nest, where its pyriform egg shape provided stability and allowed safe manoeuvrability during incubation. On the basis of a recent phylogeny of the Alcidae, we speculate that a single brood patch, a pyriform egg and upright incubation posture, as in the Great Auk and the two Uria guillemots, is the ancestral state, and that the Razorbill – the Great Auk's closest relative – secondarily evolved two brood patches and an elliptical egg as adaptations for horizontal incubation, which provides flexibility in incubation site selection, allowing breeding in enclosed spaces such as crevices, burrows or under boulders, as well as on open ledges.

The importance of observer effort on the accuracy of breeding success estimates in the Common Guillemot Uria aalge

ABSTRACT Capsule: A data-thinning approach was used to assess the effects of reducing the frequency of nest-checks on estimates of breeding success of Common Guillemots Uria aalge. Inter-year and inter-colony differences in fledging age and their implications for setting a minimum age after which a chick could be assumed to have fledged were evaluated. Aims: To assess the consequences of reducing sampling frequency on the estimation of breeding success, and on the robustness of the assumption that breeding has been successful if a chick survives to 15 days old. Methods: Breeding success, ages at fledging and loss of chicks were estimated from daily checks at two Scottish colonies over a six-year period. Data-thinning was used to assess the consequences of reducing checks from daily to every two or three days. Breeding success was recalculated assuming that all chicks surviving to 15 days fledged. Results: Reducing the frequency of checks from daily to every second or third day resulted in a small but statistically significant increase in the estimate of success. Between 20% and 25% of chick losses occurred when chicks were ≥15 days old. Assuming that these chicks had fledged resulted in significant increases in breeding success. Conclusion: Assumptions about whether or not a chick fledged had a greater impact on the estimate of breeding success than reducing the frequency of nest-checks from daily to every second or third day. There was no threshold age after which a chick could be assumed to have fledged. These findings are relevant to other monitoring schemes where there is pressure to reduce input. Sampling methods used in monitoring schemes need to be clearly stated and changes in protocols documented so that sampling effects can be incorporated into future analyses.

Effects of body size, sex, parental care and moult strategies on auk diving behaviour outside the breeding season

Information on seabird foraging behaviour outside the breeding season is currently limited. This knowledge gap is critical as this period is energetically demanding due to post‐fledging parental care, feather moult and changing environmental conditions. Based on species’ body size, post‐fledging parental strategy and primary moult schedule we tested predictions for key aspects of foraging behaviour (maximum dive depth (MDD), daily time submerged (DTS) and diurnal dive activity (DDA)) using dive depth data collected from three seabird species (common guillemot Uria aalge, razorbill Alca torda and Atlantic puffin Fratercula arctica) from the end of the breeding season (July) to mid‐winter (January). We found partial support for predictions associated with body size; guillemots had greater MDD than razorbills but MDD did not differ between razorbills and puffins, despite the former being 35% heavier. In accordance with sexual monomorphism in all three species, MDD did not differ overall between the sexes. However, in guillemots and razorbills there were sex‐specific differences, such that male guillemots made deeper dives than females, and males of both species had higher DTS. In contrast, there were no marked sex differences in dive behaviour of puffins in July and August in accordance with their lack of post‐fledging parental care and variable moult schedule. We found support for the prediction that diving effort would be greater in mid‐winter compared to the period after the breeding season. Despite reduced daylight in mid‐winter, this increase in DTS occurred predominantly during the day and only guillemots appeared to dive nocturnally to any great extent. In comparison to diving behaviour of these species recorded during the breeding season, MDD was shallower and DTS was greater during the non‐breeding period. Such differences in diving behaviour during the post‐breeding period are relevant when identifying potential energetic bottlenecks, known to be key drivers of seabird population dynamics.

Foraging behaviour of Razorbills Alca torda during chick-rearing at the largest colony in the Baltic Sea

ABSTRACTCapsule: 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.