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Confirmation of a wintering ground of Ross's Gull Rhodostethia rosea in the northern Labrador Sea 下载免费PDF全文
Ross's Gull Rhodostethia rosea is one of the world's least known seabirds; < 1% of the estimated global population can be accounted for at known breeding sites, and its wintering range has never been determined. Anecdotal reports over the last two centuries have prompted extensive speculation as to possible wintering areas used by this species in the north Pacific/Bering Sea region, but none has ever been confirmed. Using satellite and geolocator telemetry, we show that some Ross's Gulls from a colony in the Canadian Arctic winter in a restricted area of the northern Labrador Sea. Our discovery of a wintering area in the northwest Atlantic indicates that Ross's Gulls breeding in the Nearctic may be part of a disjunct population, or that birds breeding in the Palaearctic may winter off the east coast of North America. 相似文献
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2008-2010年,对青海可鲁克湖的水鸟季节动态进行了调查。共记录到54种34828只水鸟,隶属于6目11科,雁鸭类水鸟最多,共统计到28445只,占水鸟总数的81.7%;其次是鸥类和鸻鹬类。可鲁克湖在水鸟春秋季迁徙高峰期在4月和10月,这也是水鸟多样性较高的两个月,其主要原因是由于迁徙鸭类数量和种类的增加。卫星跟踪表明,可鲁克湖是青海湖繁殖渔鸥重要的停歇地,渔鸥在可鲁克湖的停歇天数每年也有所不同,2007年和2008年秋季较2006年停歇时间短一些,初步判断与当地的人为干扰有关。当地政府对道路进行修建,其正好位于渔鸥的活动区内,这对渔鸥的日常活动造成较大影响,迫使渔鸥提前离开可鲁克湖。春季停歇天数的不同主要与青海湖面冰融的时间有关,若青海湖由于温度较高,冰融的时间早一些,渔鸥可能提前离开可鲁克湖,前往青海湖进行繁殖活动。 相似文献
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Capsule Woodland birds were significantly less likely to occur in gardens in years of high beechmast crop. Aim To test the hypothesis that woodland species that feed on beechmast will have significantly lower occurrence rates at garden feeders in mast years. Methods Weekly winter occurrence rates at garden feeders between 1970/71 and 1999/2000 for 40 species were analysed in relation to annual beechmast abundance, classified into low, medium and high years. A repeated-measures logistic regression model was used to assess whether beechmast abundance explained further significant variation additional to underlying seasonal and annual trends. Results Seven species that commonly feed on beechmast showed significantly lower occurrence in gardens in years of highest beechmast abundance: Great Spotted Woodpecker Dendrocopos major, Woodpigeon Columba palumbus, Great Tit Parus major, Coal Tit Periparus ater, Nuthatch Sitta europaea, Jay Garrulus glandarius and Chaffinch Fringilla coelebs. Blackbird Turdus merula and Siskin Carduelis spinus, which showed similar significant patterns, are likely to take beechmast as elements of their diet. Pied Wagtail Motacilla alba was the only insectivorous species to show significant effects, but occurrence was lowest in years of intermediate beechmast abundance. For the latter species, this may have been due to confounding effects of temperature, but there were no such confounding effects of either temperature, or the number of bird feeders provided in gardens, for the other nine species. Conclusion Use of artificial food sources by birds in gardens is influenced by resources in the surrounding countryside, suggesting that food provided in gardens may play a significant part in the population dynamics of these species, that population monitoring without consideration of the garden habitat may be deficient, and that volunteer-based garden bird recording may provide data that can be used as an indicator of changes in the wider countryside. 相似文献
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Capsule The gulls adjust their diet composition and diversity according to refuse dump accessibility. Aims To examine the influence of the accessibility of open-air refuse dumps on the pre-laying diet of the adult Yellow-legged Gull. Methods We studied six colonies settled on six rocky islands off the southeastern coast of France. A comparative study of the diet of breeding adults from the six colonies was made through pellet analysis (a total of 848 pellets). We determined the main foraging habitat used (refuse dumps, terrestrial habitats, marine habitat) and the number of foraging habitats used simultaneously (one, two or three), from which we deduced the mean diet diversity. Results Refuse dumps were consistently the main foraging habitat (evidence in 53–74% of pellets) for the six colonies, even when refuse dump accessibility was low. The majority of pellets contained materials from two simultaneous foraging habitats (evidence in 50–64% of pellets). We demonstrated the influence of a gradient of refuse dump accessibility in terms of adjustment of the pre-laying adult's diet. Indeed, high refuse dump accessibility leads to a poorly diversified diet dominated by refuse. In contrast, when refuse dump accessibility is low, Yellow-legged Gulls broaden their trophic niche, with an increased exploitation of alternative foraging habitats, such as terrestrial habitats. Conclusion These results show the species' opportunistic feeding and high adaptability, two parameters which need to be known to foresee the consequences on population dynamics, feeding and predatory behaviour of a sudden and severe food shortage, for example due to closure of open-air refuse dumps. 相似文献
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Kentaro Kazama 《Ecological Research》2007,22(4):613-618
In colonial seabirds, nesting density, egg-laying date and nest microhabitat affect the probability of eggs being taken by
avian predators. Jungle Crows (Corvus macrorhynchos) are dominant predators of eggs of Black-tailed Gulls (Larus crassirostris). Factors affecting the probability of gulls allowing the crows to attack their nests or depredate their eggs and the probability
of eggs being taken were studied by direct observation and egg census, respectively. The effect of vegetation heights, position
in the colony, egg-laying date and neighbour nests on the probability of eggs being taken were examined at multiple spatial
scales. Gull nests were depredated more easily by larger groups of crows. Nests in peripheral areas (<4 m from the edge of
the colony) were also depredated more easily by the crows walking on the ground. Although the nests where eggs were laid early
in the season were depredated more frequently, such nests highly synchronised in egg laying within a <2-m radius were less
likely to be depredated than less-synchronised nests. The nests in tall vegetation were less likely to be depredated though
those having neighbour nests in tall vegetation were not. The number of neighbour nests did not affect the probability of
eggs being taken. Antipredation effects of nesting microhabitats vary with spatial scales at which the crows search and attack
the nests of gulls. 相似文献
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Abstract. Fagus grandifolia var. mexicana seedling dynamics were studied in a relict forest inside the crater of a volcano where it is the only canopy tree species. The objectives of the study were (1) to determine changes in seedling density before and after a mast year, as well as to monitor seedling recruitment, mortality and growth rate in relation to the micro‐environment, and (2) to discuss the impact of masting on seedling dynamics of the population. Before masting, seedling density was 8.8 seedlings m–2, afterwards seedling density peaked at 51.5 seedlings m–2, then decreased by 50% in 3 months and by 85% after 8 months, down to levels of before the mast year (9.9 seedlings m–2) after 16 months. Seedlings in the forest floor before the mast‐seeding event showed a low relative growth rate – 0.14 mm mm–1 mo–1 against 1.27 mm mm–1 mo–1 for seedlings that emerged immediately after masting. Seed germination was high (83%) and rapid (L50= 7 days) following masting. Seedling growth was positively correlated with soil water content but not with temperatures and relative humidity. Data suggested that seed production in mast years is important in maintaining the seedling bank, and thus the viability of relict Fagus populations. 相似文献
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Eric W.M. Stienen Peter Desmet Bart Aelterman Wouter Courtens Simon Feys Nicolas Vanermen Hilbran Verstraete Marc Van de Walle Klaas Deneudt Francisco Hernandez Robin Houthoofdt Bart Vanhoorne Willem Bouten Roland-Jan Buijs Marwa M. Kavelaars Wendt Müller David Herman Hans Matheve Alejandro Sotillo Luc Lens 《ZooKeys》2016,(555):115-124
In this data paper, Bird tracking - GPS tracking of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast is described, a species occurrence dataset published by the Research Institute for Nature and Forest (INBO). The dataset (version 5.5) contains close to 2.5 million occurrences, recorded by 101 GPS trackers mounted on 75 Lesser Black-backed Gulls and 26 Herring Gulls breeding at the Belgian and Dutch coast. The trackers were developed by the University of Amsterdam Bird Tracking System (UvA-BiTS, http://www.uva-bits.nl). These automatically record and transmit bird movements, which allows us and others to study their habitat use and migration behaviour in great detail. Our bird tracking network is operational since 2013. It is funded for LifeWatch by the Hercules Foundation and maintained in collaboration with UvA-BiTS and the Flanders Marine Institute (VLIZ). The recorded data are periodically released in bulk as open data (http://dataset.inbo.be/bird-tracking-gull-occurrences), and are also accessible through CartoDB and the Global Biodiversity Information Facility (GBIF). 相似文献