Glaucous-winged Gulls Larus Glaucescens Research Articles

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.

Inventory of Lowland-Breeding Birds on the Alaska Peninsula

Abstract We conducted the first systematic inventory of birds in the lowlands (areas ≤100 m above sea level) of the Alaska Peninsula during summers of 2004–2007 to determine their breeding distributions and habitat associations in this remote region. Using a stratified random survey design, we allocated sample plots by elevation and land cover with a preference for wetland cover types used by shorebirds, a group of particular interest to land managers. We surveyed birds during 10-min counts at 792 points across 52, 5 km × 5 km sample plots distributed from south of the Naknek River (58.70°N,157.00°W) to north of Port Moller (56.00°N,160.52°W). We detected 95 bird species including 19 species of shorebirds and 34 species (36% of total) considered at the time to be of conservation concern for the land managers in the region. The most numerous shorebirds on point counts were dunlin Calidris alpina, short-billed dowitcher Limnodromus griseus, and Wilson's snipe Gallinago delicata. We found the breeding-season endemic marbled godwit Limosa fedoa beringiae at 20 plots within a 3,000-km2 area from north of Ugashik Bay to just north of Port Heiden and east to the headwaters of the Dog Salmon and Ugashik rivers. The most abundant passerines on point counts were American tree sparrow Spizelloides arborea, Lapland longspur Calcarius lapponicus, and savannah sparrow Passerculus sandwichensis. Sandhill crane Antigone canadensis, glaucous-winged gull Larus glaucescens, and greater scaup Aythya marila were also relatively abundant. We categorized habitat associations for 30 common species and found that lowland herbaceous vegetation supported wetland-focused species including sandhill crane, marbled godwit, short-billed dowitcher, and dunlin; whereas, dwarf shrub-ericaceous vegetation supported tundra-associated species such as willow ptarmigan Lagopus lagopus, rock sandpiper Calidris ptilocnemis, and American pipit Anthus rubescens. Tall shrub vegetation was important to several species of warblers and sparrows, as well as one species of shorebird (greater yellowlegs Tringa melanoleuca). We found that point counts augmented with incidental observations provided an almost complete inventory of lowland-breeding species on the study area. These data form a baseline to monitor any future changes in bird distribution and abundance on the Alaska Peninsula.

RADIONUCLIDES IN MARINE FISHES AND BIRDS FROM AMCHITKA AND KISKA ISLANDS IN THE ALEUTIANS: ESTABLISHING A BASELINE

Amchitka Island (51degrees N lat, 179 degrees E long) was the site of three underground nuclear tests from 1965-1971. There have been no substantive studies of radionuclides in marine fishes and birds in the area since the mid-1970's. In this study, levels of 60Co, 52Eu, 90Sr, 99Tc, 129I, 137Cs, and the actinides (241Am, 238Pu, 239,240Pu, 234U, 235U, 236U, and 238U) were studied in ten marine fish species (including Pacific Cod Gadus macrocephalus and Pacific Halibut Hippoglossus stenolepis) and five marine bird species (including Glaucous-winged Gulls Larus glaucescens, Tufted Puffins Fratercula cirrhata, and Common Eider Ducks Somateria mollissima) from Amchitka. The same species were collected at a reference site, Kiska Island (52 degrees N lat; 177 degrees E long), about 130 km west of Amchitka. Each sample was a composite of edible muscle from five or more individual fish or birds of similar size (+/-15%) from the same sampling station. The null hypotheses of no differences among species or between Amchitka and Kiska were tested. Most analytic results were below the minimum detectable activity (MDA), even when 1,000 g sizes and 72 h counting times were used. The only radionuclides detected above the MDA were 137Cs, 241Am, 239,240Pu, 234U, 235U, and 238U. There were significant differences in 137Cs as a function of species, but not location, for top predatory fishes. Of the fishes, eight of ten species had 137Cs values above the MDA for some samples; only one bird, Glaucous-winged Gull, had 137Cs values above the MDA. The highest concentrations of 137Cs were in Dolly Varden [Salvelinus malma, 0.780 (Bq kg(-1) wet weight)] and Pacific Cod (0.602 Bq kg(-1)). In aggregate for any actinides, 73 of 234 (31%) composites for fish were above the MDA, compared to only 3 of 98 (3%) for birds. 234U and 238U, radionuclides that are primarily natural in origin, were routinely detected in these biological samples, but there were no significant differences in mean concentrations between Amchitka and Kiska. The concentrations of all radionuclides examined at Amchitka are similar to those of other uncontaminated Northern Hemisphere sites, and are lower than those reported for fishes and birds from the Irish Sea in the vicinity of the Sellafield nuclear reprocessing facility, an area with known contamination.

Size- and Sex-Selective Mortality of Adult Sockeye Salmon: Bears, Gulls, and Fish Out of Water

Abstract Pacific salmon Oncorhynchus spp. exist as reproductively isolated breeding populations and display marked variation in size and age at maturity within and among populations. We conducted a detailed study of mortality on adult sockeye salmon O. nerka in Hansen Creek, a small stream in southwestern Alaska, to test the prediction that predation by brown bears Ursus arctos and death by stranding during upstream migration would selectively remove males and large (old) individuals. During the 3 years of this study, 13.7% of the mature salmon died in shallow water at the creek's mouth before reaching the spawning grounds. Males had proportionally higher mortality at the mouth than females (17.6% versus 10.8%), and the fish of both sexes that died at the mouth were larger and older than those that survived to ascend the creek. Of the fish that died at the mouth, females were more often attacked (chiefly scavenged) by glaucous-winged gulls Larus glaucescens than males, and the gulls tended to attack fish ...

An Evaluation of Marine Bird Population Trends Following the ExxonValdez Oil Spill, Prince William Sound, Alaska

We examined post-spill trends (1989–1998) of marine bird populations in Prince William Sound (PWS) following the Exxon Valdez oil spill (EVOS) to evaluate recovery of injured taxa. Two criteria were employed. First, we examined population trends of injured taxa only in the oiled area of PWS using regression models. Second, we examined population trends of injured taxa in the oiled area relative to the unoiled area using homogeneity of the slopes tests. We considered a population recovering if there was a positive trend using either criteria. We considered a population not recovering if there was no trend using either criteria or a negative trend in the oiled area. A significant negative trend in the oiled area relative to the unoiled area was considered a continuing and increasing effect. Most taxa for which injury was previously demonstrated were not recovering and some taxa showed evidence of increasing effects nine years after the oil spill. Four taxa (loons Gavia spp, Harlequin Duck Histrionicus histrionicus, Bufflehead Bucephala spp, and North-western Crow Corvus caurinus) showed weak to very weak evidence of recovery. None of these taxa showed positive trends in both winter and summer. Nine taxa (grebes Podiceps spp, cormorants Phalacrocorax spp, Black Oystercatcher Haematopus bachmani, Mew Gull Larus canus, Glaucous-winged Gull Larus glaucescens, terns Sterna spp, murres Uria spp, Pigeon Guillemot Cepphus columba, and murrelets Brachyramphus spp) showed no evidence of recovery during summer or winter. Four taxa (scoters Melanitta spp, mergansers Mergus spp, goldeneyes Bucephala spp, and Black-legged Kittiwake Rissa tridactyla) showed evidence of continuing, increasing effects. We showed evidence of slow recovery, lack of recovery, and divergent population trends in many taxa which utilize shoreline and nearshore habitats where oil is likely to persist. Potential lingering spill effects and natural variability appear to be acting in concert in delaying recovery of many PWS bird populations.

Ecological interactions and habitat modification in nesting Common Murres, Uria aalge

SummarySeabird populations suffer from a variety of natural and human-induced sources of mortality and loss of lifetime reproductive output. On the outer coast of Washington State, Common Murre Uria aalge populations have been in decline for approximately the last decade and are currently reproductively active only at Tatoosh Island. These murres nest in two basic habitat types: crevices (25% of the population) and larger cliff-top subcolonies (75%). Murres in cliff-top subcolonies have suffered dramatic reductions in reproductive success in recent years relative to conspecifics nesting in the crevices, primarily due to egg predation by Glaucous-winged Gulls Larus glaucescens and Northwestern Crows Corvus caurinus, facilitated by the presence of Bald Eagles Haliaeetus leucocephalus. Because predator removal is not feasible and creation of additional crevice habitat is difficult, expensive and potentially ineffective, we have designed a temporary habitat modification (the “silk forest”) which replaces the natural vegetation cover and modifies the interaction between murres and eagles. Within the test subcolony, murres nesting under and immediately adjacent to the silk forest produced nearly twice as many eggs per square metre as their conspecifics nesting in adjacent exposed-ground areas.

Effects of predation by birds on gooseneck barnacle Pollicipes polymerus Sowerby distribution and abundance

The California mussel Mytilus californianus Conrad and gooseneck barnacle Pollicipes polymerus Sowerby arc common, competitively dominant organisms inhabiting wave-swept rocky shores along the west coast of North America. Throughout much of their ranges, California mussels arc far more abundant than are gooseneck barnacles and previous investigators have cited morphologic constraints and interactions between these species to explain this disparity. Surfbirds Aphriza virgata (Grnelin) and gulls, primarily western gull Larus occidentalils Audubon and glaucous-winged gull Larus glaucescens Naumann, occur each winter in flocks of ≥40–100 individuals along the coast of California. On their wintering grounds, they feed almost exclusively in the intertidal zone and consume large numbers of gooseneck barnacles. A bird-exclusion experiment showed that winter feeding by shorebirds and gulls significantly reduced the abundance of Pollicipes barnacles in plots accessible to birds compared to plots from which birds had been excluded. However, predation by birds was found to be both spatially and temporally patchy. Predation by birds may account for the distribution and abundance of gooseneck barnacles along the coast of northern California. No evidence was found that either physical factors or losses through interspecific competition with the California mussel restricts the distribution of this species.

Total Body Water and Its Turnover in Free-Living Nestling Glaucous-Winged Gulls with a Comparison of Body Water and Water Flux in Avian Species with and without Salt Glands

Total body water (TBW) and its turnover were measured in free-living nestling glaucous-winged gulls Larus glaucescens. Body mass (BM) was linearly related to age, and TBW was linearly related to BM in nestlings aged 4-38 days. Equilibration of intravenously (i.v.) injected tritiated water (TOH) was complete in ½ h; intraperitoneally (i.p.) injected TOH in 1 hour. TBW, ml = -28.4 + 0.88 BM, g(r² = .99; 48 determinations, TOH dilution in nestling gulls). TBW decreased rapidly at the end of the maturation period with the largest nestlings (5) having TBW of 83.2% BM, which was higher (P < .001) than that of fledglings (5), 73.9% BM, which was higher (P < .025) than that of adults (5), 66.0% BM. TBW by TOH dilution exceeded that by desiccation to constant weight. Tissue tritium retention in growing gulls was negligible. Mean daily water flux (WF) in adult gulls (6) was 18.1% BM, and mean daily nestling water efflux (WE) was 28.6% BM, linearly related to BM over the growth period and the same during rainy and fair periods. Analysis of published data TOH studies showed that species with salt glands tended to have higher TBW and had significantly (P < .05) greater water flux: WF = 1.03 BM0.75 than species lacking salt glands, WF = 0.52 BM0.73.