Breeding density and population of little auks (Alle alle) in a Northwest Greenland colony

The little auk population of the Thule district in Greenland is generally believed to be the largest anywhere and to comprise more than half of the world population, although published numbers have largely been conjectural. In 1996/1997 we estimated breeding density of little auks at Hakluyt Island in this district by colour-marking a number of birds in three study plots and subsequently counting marked and unmarked birds present in the plots. The density estimate considered most representative of the colony was 1.8 birds/m² or 0.73 pairs/m² (±7%). From surveys of the inhabitated area of the scree slopes, this density implies a total little auk population for the island of 130,000 pairs. An extrapolation to the entire Thule district suggests a population in the area of at least 15 million pairs, which is in general agreement with previously published assumptions. Accepted: 3 January 2000     

Visual prey availability and distribution of foraging little auks (Alle alle) in the shelf waters of West Spitsbergen

As diving seabirds use vision underwater, it is presumed they should preferentially select sites where their preferred food items are not only abundant but also clearly visible. To test this, we studied the optical properties of the seawater in the West Spitsbergen Shelf, in combination with zooplankton abundance in the feeding grounds of the planktivorous little auks from the nearby colonies in Hornsund. We estimated the relative attractiveness of the foraging sites using a novel parameter—visual prey availability (VPAv), which relates density and proportion of the preferred food item (Calanus glacialis) of the little auk, in total zooplankton, to the optical properties of the seawater. We found a significant positive correlation between the density of foraging little auks and VPAv values. Birds chose areas where C. glacialis was both abundant and clearly visible, because of the clarity of the water and low proportion of other zooplankton species. The birds avoided foraging over the warmer Atlantic-type waters, characterised by a high abundance of zooplankton taxa mostly ignored by birds and where VPAv values were low. VPAv values could potentially also be applied to other visual planktivores for which prey preference and visual acuity are known.     

Flexibility in the bimodal foraging strategy of a high Arctic alcid, the little auk Alle alle

A bimodal foraging strategy has previously been described for procellariiform seabird species and is thought to have evolved in response to local resource availability being too low for adult birds to meet chick requirements and simultaneously maintain their own body condition. Here, we examine the dual foraging trip pattern of an alcid, the little auk Alle alle , at five colonies with contrasting oceanographic conditions. In spite of large variation in local conditions, little auks at all colonies showed the same general pattern of alternating a single long-trip with several consecutive short-trips. However, we found that the foraging pattern was flexible and could be adjusted at three levels: (1) the length of long-trips, (2) the frequency of short-trips, and (3) the total time spent foraging. Birds facing unfavorable conditions increased the duration of long-trips and reduced the number of short-trips. These adjustments resulted in reduced provisioning rates of chicks despite the fact that birds also increased the time allocated to foraging. Travel times during foraging trips were positively correlated to the total duration of the trip suggesting that differences in trip length among colonies were partly driven by variation in the distance to foraging areas. Most birds spent substantially more time traveling during long compared to short-trips, indicating that they accessed distant foraging areas during long-trips but remained close to the colony during short-trips. However, the difference in travel times was small at the site with the most favorable conditions suggesting that bimodal foraging in the little auk may be independent of the existence of high-quality areas at distance from the breeding ground.     

Distribution of little auk (Alle alle) breeding colonies in Thule District, northwest Greenland

Large areas with hydrocarbon prospects offshore northwest Greenland necessitate seabird studies in this region. The little auk population breeding in Thule District is the largest seabird population in northwest Greenland, as well as the largest known population of this species. In 1994 and 1995 we mapped the distribution of little auk colonies in Thule District during aerial surveys. Most colonies are situated in sloping screes facing the sea, some as far as 11 km from the coast in valleys or facing glaciers. The total horizontal extent of the colonies is about 400 km. Our surveys generally confirm previous and local knowledge, although the information obtained is more detailed. Received: 11 November 1996 / Accepted: 21 September 1997     

No evidence of extra-pair paternity in the little auk Alle alle

Extra-pair paternity is typically rather infrequent in seabirds, as in most other long-lived and socially monogamous birds. Here we report the first paternity study of the little auk Alle alle , a high arctic seabird which raises only a single chick per year. Parentage was determined using three highly polymorphic microsatellite markers. We found that all 26 chicks in our sample were true genetic offspring of their social parents, with an upper 95% confidence limit of 10.88% for the frequency of extra-pair paternity. This level of extra-pair paternity is not significantly different from frequencies reported from the closely related common Uria aalge and Brünnich's guillemots U. lomvia .     

Potentially pathogenic yeast isolated from the throat and cloaca of an Arctic colonial seabird: the little auk (Alle alle)

Yeasts are a distinctive group of microfungi, but compared to other microorganisms, their ecological function and biodiversity are poorly known. This is especially so where polar ecosystems are concerned. With climate changes and increasing pollution levels in the Arctic, it can be anticipated that there will be an increase in the prevalence and diversity of fungi colonizing live organisms. With these changes, it is crucial to investigate and monitor species diversity and prevalence of fungi in this fragile environment. In this study, yeasts were examined from throat and cloaca of a small colonial seabird, the little auk (Alle alle), a keystone species in the Arctic ecosystem. Samples were collected from 94 adults and 17 nestlings in breeding colony in Magdalenefjorden (NW Spitsbergen) in 2009. In total, twelve species of yeast from eight genera were found in 12 % of the samples, with the Dipodascus genus being the most prevalent. All yeast species were found in the adults, but only one species, Cryptococcus macerans, was found in a single nestling. In individuals where fungus was isolated, it was only isolated from either the throat or the cloaca, except for two cases, where fungus was found in both throat and cloaca. The presence of yeast was not related to sex but age of the birds, with adults being more prone to colonization by yeasts than the nestlings. The relatively low prevalence and diversity of yeast in little auks suggest that these birds are random carriers of fungi, with minor health impacts.     

Composition of chick meals from one of the main little auk (Alle alle) breeding colonies in Northwest Greenland

During the last decade, increasing information on little auk (Alle alle) biology, ecology and behaviour has been reported. However, only a few of these studies have focused on the breeding population in the Avanersuaq (Thule) district of Northwest Greenland, where 80 % of the global little auk population is estimated to breed. This study reports on the chick diet composition from one of the largest colonies, the Paakitsoq colony, located on the south-eastern margin of the North Water (NOW) Polynya. Results revealed the highest proportion of Calanus hyperboreus, a large lipid-rich copepod, in chick diet reported for any little auk colony. Results confirmed that the cold, highly productive waters of the NOW Polynya are favourable foraging grounds for the little auks during the breeding season. Species diversity within and between the chick meals was low, which probably reflects a high availability of a few preferred prey species. Individual chick meals were generally low in number of prey items and total energy content compared with other published results. This may be explained by a higher feeding frequency or by the samples being collected late in the breeding period (during late chick rearing), when chicks have a reduced growth rate and may require less energy than at earlier developmental stages.     

Winter diet of the little auk (Alle alle) in the Northwest Atlantic

The little auk (Alle alle) is one of the most numerous seabirds in the world, but their winter prey selection has never been thoroughly studied. In the present study, we analyzed the proventricular contents of 205 little auks caught in coastal areas off southwest Greenland during December–February and off Newfoundland in March. Large Calanoid copepods are known to be the main prey during summer. We found krill to become the crucial winter prey in both areas, followed by Themisto spp. and young capelin (Mallotus villosus). No difference was found between the diet of juvenile and adult birds. Copepods constituted around 1 % of the diet and close to all copepods were in birds caught near Cape Farwell in December. These findings provide new and important insight into the forage ecology of the little auk, and they support other studies showing that large Calanoid copepods in the Arctic decent for winter hibernation at depths that are below the diving range of the little auks. More studies to determine offshore diet and annual variation are, however, needed in order to get a more complete picture.     

Summer at-sea distribution of little auks Alle alle and harp seals Pagophilus (Phoca) groenlandica in the Fram Strait and the Greenland Sea: impact of small-scale hydrological events

Among the most numerous seabird and pinniped species of the Fram Strait and the Greenland Sea, little auks Alle alle and harp seals Pagophila (Phoca) groenlandica are very abundant in the mixed Polar/Arctic Waters at the front between the two water masses. This must reflect the presence of very high concentrations of their food, Arctic zooplankton and nekton, massively attracting their predators. Such a high biological production seems to be depending on new primary production based on upwelling and high nutrient concentration. This usually takes place at the ice edge (e.g. July 2005), but hydrological conditions such as eddies can modify its position, east of the front in open water as caused by a subsurface eddy (August 2005), or in ice-covered areas if westerly winds push the pack ice to the east, eventually covering an eddy and causing very high concentrations of little auks and harp seals (July 2008). On the other hand, a dramatic decrease of pack ice coverage can move this water mass farther north and west, making it inaccessible to little auks during their breeding season, and apparently causing breeding failure in Jan Mayen in July 2005. In future years, if a much stronger diminution in sea ice coverage will take place, similar to the retreat in 2005 and 2007, the failure might affect the whole Spitsbergen population, as well as other seabird species feeding mainly at the ice edge.     

The finding of a cestode in the little auk Alle alle on Franz Josef Land

One of 14 dovekeys (Alle alle) investigated in August 1993 on Hooker Island (Franz Joseph Land) was found to harbour a single specimen of an early immature dilepidid cestode attributed as Alcataenia sp. The rostellum bears a double crown of 22 hooks, 0.025-0.027 mm in length. Except Threlfall (1971) there was no information concerning dovekey's parasites.     

Variation in faecal corticosterone metabolites in an Arctic seabird,the Little Auk (Alle alle) during the nesting period

Glucocorticoids participate in the control of whole body homoeostasis and an organism’s response to stress. Corticosterone, which is the principal glucocorticoid in birds, has been shown to increase in response to different energetic demands and perturbations that individuals have to cope with. In this study, a non-invasive method to examine the corticosterone secretion by measuring faecal corticosterone metabolites (FCM) has been established for an Arctic seabird, the Little Auk (Alle alle). A group-specific immunoassay was successfully validated for adults and chicks using an adrenocorticotropic challenge test. Then, FCM levels were investigated under different energetic and physiological demands, determined by weather conditions, week of chick rearing in adults, and age in chicks. The amount of rainfall had no effect on FCM levels in adults, whereas it negatively affected FCM levels in chicks. There was no variation in FCM concentrations among weeks of chick rearing in adults. In chicks, the FCM levels increased with age. Moreover, chicks with higher FCM levels had lower body mass and fledged later than chicks with lower FCM levels. This study demonstrates that environmental stress such as poor weather conditions can trigger significant changes in corticosterone levels in seabird chicks. Furthermore, the results indicate that corticosterone may be involved in the physiological and behavioural adjustments necessary for successful fledging and post-fledging survival.     

Rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata breeding in a seasonal environment

We removed first eggs from early‐laying females to measure rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata at Triangle Island, British Columbia, Canada. Based on egg size and composition, the investment that Cassin's auklets made in first eggs was very close to that predicted from adult body mass, whereas rhinoceros auklets invested more. In both species, a high percentage of females relaid (90% of Cassin's and 87% of rhinoceros auklets). Breeding success declined weakly with later laying among control Cassin's auklet pairs, but pairs that we induced to relay bred more successfully than naturally late pairs, and similar to values predicted from laying dates of their first eggs. Their chicks also fledged heavier and younger than late control chicks, and similar to values in early control chicks, but followed the population‐wide seasonal decline in wing length at fledging. Nestling diets were dominated by Neocalanus copepods until late in the season, a sign that feeding conditions remained favourable until late. In contrast, rhinoceros auklet pairs induced to relay followed the population‐wide seasonal decline in breeding success, which was driven by a decline in hatching success. Pacific sandlance Ammodytes hexapterus, thought to be a preferred prey species, virtually disappeared from nestling diets in mid‐to‐late season, yet there was no seasonal decline in fledging mass. However, chicks from replacement eggs followed the declines among control chicks in both age and wing length at fledging. Despite the female having produced a replacement egg, and despite delayed breeding, there appeared to be little immediate consequence associated with relaying for Cassin's auklets, except for a tendency for their chicks to fledge with short wings. Consequences were more marked in rhinoceros auklets (greatly reduced hatching success, and having their chicks fledge with short wings), and this may have been due to the large investment made in eggs, and/or to delayed breeding. Results of this study show that attributes of Cassin's and rhinoceros auklets that lay at different times in the season can be important in driving seasonal declines in breeding performance, as found in studies on other Alcidae. They also show how decisions taken during the egg stage can have variable yet potentially important implications for fitness, even in relatively long‐lived species that lay single‐egg clutches.     

Eggs in the freezer: energetic consequences of nest site and nest design in Arctic breeding shorebirds

Birds construct nests for several reasons. For species that breed in the Arctic, the insulative properties of nests are very important. Incubation is costly there and due to an increasing surface to volume ratio, more so in smaller species. Small species are therefore more likely to place their nests in thermally favourable microhabitats and/or to invest more in nest insulation than large species. To test this hypothesis, we examined characteristics of nests of six Arctic breeding shorebird species. All species chose thermally favourable nesting sites in a higher proportion than expected on the basis of habitat availability. Site choice did not differ between species. Depth to frozen ground, measured near the nests, decreased in the course of the season at similar non-species-specific speeds, but this depth increased with species size. Nest cup depth and nest scrape depth (nest cup without the lining) were unrelated to body mass (we applied an exponent of 0.73, to account for metabolic activity of the differently sized species). Cup depth divided by diameter(2) was used as a measure of nest cup shape. Small species had narrow and deep nests, while large species had wide shallow nests. The thickness of nest lining varied between 0.1 cm and 7.6 cm, and decreased significantly with body mass. We reconstruct the combined effect of different nest properties on the egg cooling coefficient using previously published quantitative relationships. The predicted effect of nest cup depth and lining depth on heat loss to the frozen ground did not correlate with body mass, but the sheltering effect of nest cup diameter against wind and the effects of lining material on the cooling coefficient increased with body mass. Our results suggest that small arctic shorebirds invest more in the insulation of their nests than large species.     

Differences in food abundance cause inter-annual variation in the breeding phenology of High Arctic waders

Previous work has shown that High Arctic waders in Greenland are “income breeders”, i.e. the resources used for egg formation are based almost entirely on biomass obtained on the breeding grounds. Thus, their breeding phenology is expected to be highly sensitive to inter-annual variation in food abundance during the pre-laying period. Early spring snow-cover may also influence timing of egg-laying either directly or mediated through food resources. Here, we report on the inter-annual variation in clutch initiation of three wader species breeding in High Arctic Greenland, Sanderling (Calidris alba), Dunlin (Calidris alpina) and Ruddy Turnstone (Arenaria interpres), in relation to spring snow-cover and spring arthropod abundance over ten breeding seasons at Zackenberg Research Station 1995–2005. Food abundance had the strongest effect on timing of clutch initiation, while the proportion of snow-free land had a weaker but still significant effect, i.e. more food and more snow-free land both result in earlier egg-laying. We hypothesize that food is most important when there is sufficient snow-free land to nest on, while snow-cover is of increasing importance in years with late snowmelt.     

The effect of egg size on post-hatching development in the Razorbill: an experimental study

A recent experimental study reported that Thick-billed Murre Uria lomvia chicks that hatched from large eggs grew their wing feathers more quickly than did small-egg chicks. There is little evidence of this (or any other) egg-size effect on post-hatching development in other birds. Thick-billed Murres are marine birds of the family Alcidae that employ the unique "intermediate" developmental strategy: chicks go to sea after 15-30 days at the nest site, at <30% of adult mass, accompanied by their male parent. Rapid feather growth during the brief nestling period is critical to enable chicks to make the transition from life at the nest site to life at sea quickly and safely. At the Gannet Islands, Labrador, Canada, in 1996 and 1997, I tested whether egg size has the same effect on wing-feather growth in the Razorbill Alca torda , another of the intermediate auks. To control for underlying correlations between egg size and other parental attributes, eggs were switched randomly among pairs. As in other birds, egg size strongly predicted hatchling mass, and to less extent hatchling size (tarsus length), but had no effect on the rate at which nestlings gained mass. However, egg size had the same effect on wing growth in Razorbills as in Thick-billed Murres: the wings of large-egg chicks began rapid, linear growth sooner, indicating that early development of wing feathers was enhanced in large-egg chicks. Differences in wing length established in this manner persisted through the nestling period. Egg-size effects on feather growth have not been detected in experimental studies on other birds, suggesting that effects of the magnitude seen in Razorbills and Thick-billed Murres might reflect evolutionary priorities in the post-hatching development of intermediate auks.     

A comparative study of the diet of auks killed during an oil incident in the Skagerrak in January 1981

Stomach contents were examined from guillemots Uria aalge (Pont.), Razorbills Alca torda Linnaeus and Little auks Alle alle (Linnaeus) killed by oil in the Skagerrak in January 1981. The range of prey species was small; the commonest fish found in the stomachs were Gobiusculus flavescens (Fabricius), Crystallogobius linearis (Düben), Sprattus sprattus (L.), Trisopterus minutus (L.) and Ammodytes sp. The relative importance of these fish depended on bird species and locality. Guillemots contained gadoids more frequently and sandeels less frequently than razorbills, and the composition of guillemot samples from Oslo Fjord differed from that of samples from Sweden. Invertebrate remains were uncommon in all bird species; the commonest items recorded were polychaete jaws. The frequency of occurrence of items in the diet of guillemots from Oslo Fjord was apparently influenced by the extent of oiling suffered by the birds.     

Maternal investment during egg laying and offspring sex: an experimental study of zebra finches

To study whether offspring sex is related to the amount of resources invested in eggs we performed an experiment on zebra finches, Taeniopygia guttata. By manipulating their food supply, we forced two groups of females either to increase or to decrease investment in subsequent eggs. Since zebra finches are sexually dimorphic and the reproductive value of the sexes may vary with maternal nutritional status, we predicted that females would adjust the sex of their offspring to egg quality. Females that received poor-quality food for 7 weeks before egg laying, then food supplemented with proteins after they laid the first egg, significantly increased the mass of subsequent eggs. An increase of egg mass with laying sequence was less pronounced in females that received high-quality food before laying and experienced food deterioration after starting to lay. The proportion of sons in subsequent eggs tended to increase in the latter group (although this was marginally significant) but was not related to laying sequence in the other group: these patterns differed significantly between the groups. Offspring sex was not related to egg mass, but newly hatched male chicks were heavier than female chicks. Furthermore, the hatching success of male eggs was lower than that of female eggs. We suggest that differential hatching success of the sexes and sex differences in mass at hatching may constitute important factors shaping brood sex ratios. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.