Sympatric Breeding Auks Shift between Dietary and Spatial Resource Partitioning across the Annual Cycle

When species competing for the same resources coexist, some segregation in the way they utilize those resources is expected. However, little is known about how closely related sympatric breeding species segregate outside the breeding season. We investigated the annual segregation of three closely related seabirds (razorbill Alca torda , common guillemot Uria aalge and Brünnich’s guillemot U . lomvia ) breeding at the same colony in Southwest Greenland. By combining GPS and geolocation (GLS) tracking with dive depth and stable isotope analyses, we compared spatial and dietary resource partitioning. During the breeding season, we found the three species to segregate in diet and/or dive depth, but less in foraging area. During both the post-breeding and pre-breeding periods, the three species had an increased overlap in diet, but were dispersed over a larger spatial scale. Dive depths were similar across the annual cycle, suggesting morphological adaptations fixed by evolution. Prey choice, on the other hand, seemed much more flexible and therefore more likely to be affected by the immediate presence of potential competitors.     

Inter-breeding movements of little auks <Emphasis Type="Italic">Alle alle</Emphasis> reveal a key post-breeding staging area in the Greenland Sea

Seabirds are important components in marine ecosystems. However, knowledge of their ecology and spatial distribution during the non-breeding season is poor. More investigations during this critical period are required urgently, as marine environments are expected to be profoundly affected by climate change and human activities, with both direct and indirect consequences for marine top predators. Here, we studied the distribution of little auks (Alle alle), one of the most abundant seabird species worldwide. We found that after the breeding season, birds from East Greenland quickly travelled north-east to stay for several weeks within a restricted area in the Greenland Sea. Activity patterns indicated that flying behaviour was much reduced during this period, suggesting that this is the primary moulting region for little auks. Birds then performed a southerly migration to overwinter off Newfoundland. These preliminary results provide important information for the conservation of this species and emphasise the need for further studies at a larger spatial scale.     

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     

The diet of common eiders wintering in Nuuk,Southwest Greenland

Southwest Greenland provides wintering grounds for 70% (∼460,000) of the northern common eider (Somateria mollissima borealis) population. From 241 gullet samples (esophagus and proventriculus content) collected over three winters (1999–2002) near Nuuk, we identified 39 species consumed by the eiders. In contrast to studies elsewhere, fresh mass of the diet was dominated by soft-bottom species: the bivalve Mya eideri (32.8%) and the polychaete Pectinaria spp. (24.2%). The hard-bottom blue mussel (Mytilus edulis), usually the dominant prey of common eiders, was only the fourth most important diet species (7.5%). Overall, bivalves accounted for 56% of the diet. Twenty-seven prey species were minor foods with aggregate fresh mass of only 5.5%. Diets of males and females were similar, whereas juveniles consumed greater mass of crustaceans and less of bivalves. Diet diversity was higher in mid-winter than late winter, and higher in coastal habitats than in fjords. Within one important wintering area the results indicate that optimal size of blue mussels may be depleted over winter.     

Latitudinal gradients in sea ice and primary production determine Arctic seabird colony size in Greenland

Sea ice loss will indirectly alter energy transfer through the pelagic food web and ultimately impact apex predators. We quantified spring-time trends in sea ice recession around each of 46 thick-billed murre (Uria lomvia) colonies in west Greenland across 20 degrees of latitude and investigated the magnitude and timing of the associated spring-time primary production. A geographical information system was used to extract satellite-based observations of sea ice concentration from the Nimbus-7 scanning multichannel microwave radiometer (SMMR, 1979-1987) and the Defence Meteorological Satellite Programs Special Sensor Microwave/Imager (SSMI, 1987-2004), and satellite-based observations of chlorophyll a from the moderate resolution imaging spectroradiometer (MODIS: EOS-Terra satellite) in weekly intervals in circular buffers around each colony site (150 km in radius). Rapid recession of high Arctic seasonal ice cover created a temporally predictable primary production bloom and associated trophic cascade in water gradually exposed to solar radiation. This pattern was largely absent from lower latitudes where little to no sea ice resulted in a temporally variable primary production bloom driven by nutrient cycling and upwelling uncoupled to ice. The relationship between the rate and variability of sea ice recession and colony size of thick-billed murres shows that periodical confinement of the trophic cascade at high latitudes determines the carrying capacity for Arctic seabirds during the breeding period.     

Timing of epiphyseal development in the flipper skeleton of the harbour porpoise (Phocoena phocoena) as an indicator of paedomorphosis

Epiphyseal development was investigated on X‐rays of flippers from 158 harbour porpoises from Danish waters. Development followed a proximodistal pattern similar to what is known in other cetacean species. Ossification of epiphyses was rare in the phalanges of the first and fifth digits and in the more distal phalanges of the second, third and fourth digits. Along with the morphology of the first metacarpal and the more distal phalanges this suggested paedomorphosis relative to delphinids. Male and female porpoises showed similar progression of epiphyseal development until approximately the sixth year. From then on, female porpoises showed more progressed development than males. This suggests a higher level of paedomorphosis in the male porpoise. The mechanism behind phocoenid paedomorphosis seems to be progenesis, probably as an adaptation towards a high reproductive rate relative to the delphinids.     

Declining trends in the majority of Greenland’s thick-billed murre (Uria lomvia) colonies 1981–2011

Large population declines were reported for the thick-billed murre (Uria lomvia) in Greenland for the period 1930s–1980s, but no national status has been published for the past 20 years. Meanwhile, the murres have gained more protection and several human-induced mortality factors have been markedly reduced. Here, we give an updated status based on the past 30 years of murre count data. The total Greenland population in 2011 was estimated to 468,300 birds (95 % CI 430,700–505,900) or around 342,000 breeding pairs, distributed within 19 colonies. This represents an overall reduction of 13 % since the mid-/late 1980s. In the same period, five colonies went extinct. Large and apparently stable colonies in Qaanaaq (Northwest Greenland) account for more than half the population (68 %), but most other colonies declined heavily, with up to 6 % p.a. in the most critical areas. So far, nothing indicates that food is a limiting factor in Greenland during the breeding season, although rather few colonies have been studied in details. In contrast, illegal hunting and disturbances during the breeding season are still a problem in Greenland, despite more restrictive hunting regulations, and may explain much of the continued population decline. In addition, recent studies from Svalbard indicate that a large-scale deterioration of the marine environment in the North Atlantic, due to oceanographic changes, may impact recruitment to some of the Greenland colonies. Murre colonies in southern Upernavik, Disko Bay, South Greenland and East Greenland are in urgent need of additional conservation initiatives to avoid further declines and local extinctions.     

Effects of implanted satellite transmitters on behavior and survival of female common eiders

Surgically implanted satellite transmitters have been widely used in studies of avian ecology, yet little is known about their potential impacts on birds. We implanted satellite transmitters with percutaneous antennae (approx. 50 g) in 17 female common eiders (Somateria mollissima) at a breeding colony in Arctic Canada. Among females implanted during incubation, 11 of 12 nests were abandoned within 1 week of being radioed. We observed no differences in the proportion of time that implanted female eiders allocated to basic behaviors. Radioed birds were more likely to pick or preen their abdominal (site of surgical incision) and posterior–dorsal (site of antenna exit) regions than unmarked females, although these behaviors were rare (approx. 0.3% of total time budget). Three of 10 females re-observed had a pronounced limp following surgery, but we observed no walking difficulties among these females in subsequent seasons, and we observed some implanted eiders nesting in subsequent years. Mark–resighting models suggest eiders with transmitters had lower apparent survival the year after implantation (67.0%; 85% CI: 47.8–81.9%) than did color-banded eiders (87.5%, 85% CI: 82.5–91.2%), but there was no model support for a survival difference in subsequent years. We conclude that transmitter implantation in common eiders leads to short-term changes in behavior and a decline in first year survival. We encourage researchers to collect similar data on their study subjects where possible and use it to determine the degree to which data are representative of the greater population. © 2011 The Wildlife Society.