965 resultados para Seabird


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Mode of access: Internet.

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Senior thesis written for Oceanography 445

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Acknowledgements K. Ashbrook, M. Barrueto, K. Elner, A. Hargreaves, S. Jacobs, G. Lancton, M. LeVaillant, E. Grosbellet, A. Moody, A. Ronston, J. Provencher, P. Smith, K. Woo and P. Woodward helped in the field. J. Nakoolak kept us safe from bears. N. Sapir and two anonymous reviewers provided very useful comments on an earlier version of our manuscript. R. Armstrong at the Nunavut Research Institute, M. Mallory at the Canadian Wildlife Service Northern Research Division and C. Eberl at National Wildlife Research Centre in Ottawa provided logistical support. F. Crenner, N. Chatelain and M. Brucker customized the GPS at the IPHC-CNRS. KHE received financial support through a NSERC Vanier Canada Graduate Scholarship, ACUNS Garfield Weston Northern Studies scholarship and AINA Jennifer Robinson Scholarship and JFH received NSERC Discovery Grant funding. J. Welcker generously loaned some accelerometers. All procedures were approved under the guidelines of the Canadian Council for Animal Care.

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Partial migration has never been studied in pelagic seabirds, but investigating old unresolved questions in new contexts can provide useful fresh insights. We used geolocators and stable isotopes to investigate this phenomenon in a migratory pelagic seabird, the Cory’s shearwater (Calonectris diomedea). Although most birds migrated to the southern hemisphere, 8.1% of studied birds (N = 172) remained close to the breeding colony (Selvagem Grande, Madeira, Portugal), foraging within the Canary current. Almost all resident birds were males, while age or body size did not predict migratory status. Despite displaying a high repeatability (R = 0.72) in the choice of wintering area, residency was not a fixed strategy and individuals could switch between migrating and staying in the Canary current in different years. The predictions resulting from the “body size” and the “social dominance” hypotheses, in which larger individuals or dominant individuals, respectively, remain closer to the breeding areas, were not supported by our data. Resident males were able to occupy the nesting burrows much earlier than migratory males and arrival time in this species is known to affect the probability of engaging in a reproductive attempt. The selective pressure to arrive early at the colony is therefore the most likely explanation for the maintenance of this partial migration system.

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Bulwer'spetrelsarenocturnalseabirdsthatmostlypreyonmesopelagicfauna.Asaerialforagersand shallowdivers,theirfeedingopportunitiesarelimitedbynear-surfaceavailabilityoftheirprey,whichis highlyvariablebothtemporally(reflectingdiurnalandlunarcycles)andspatially.Herewestudiedhow Bulwer'spetrelscopewiththeseconstraintsbyanalysingtheirat-seadistributionandactivityduringthe incubationperiod.Wetrackedthemovementsof20birdsfromSelvagemGrande(NEAtlantic)duringa completelunarcycle,andrecorded30foragingtripsthatlasted11daysonaverage.Birdswereboth distributedaroundthecolonyandinwatersclosetotheAzoreanarchipelago(mid-Atlantic)located 1700kmaway,andweresignificantlymoreactiveatnight(especiallyjustaftersunsetandbeforesunrise), whenmesopelagicfaunaisalsoclosertotheseasurfaceduetotheirdielverticalmigrations.Bulwer's petrelsspentsignificantlymoretime flyingduringmoonlight,althoughtheeffectofthemoonwasrela- tivelyweak(ca.10–15%differencebetweenmoonlitanddarkperiodsofthenight),andnotobviouswhen birdswereforaginginmid-Atlanticwaters,whichwerealsotargetedmoreoftenduringfull-moon.These resultsrevealkeyadaptationsoftheBulwer'spetreltothehighlydynamicecologyofitsmesopelagicprey.

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Plants collected from diverse sites on subantarctic Macquarie Island varied by up to 30 parts per thousand in their leaf delta(15)N values. N-15 natural abundance of plants, soils, animal excrement and atmospheric ammonia suggest that the majority of nitrogen utilised by plants growing in the vicinity of animal colonies or burrows is animal-derived. Plants growing near scavengers and animal higher in the food chain had highly enriched delta(15)N values (mean = 12.9 parts per thousand), reflecting the highly enriched signature of these animals' excrement, while plants growing near nesting penguins and albatross, which have an intermediate food chain position, had less enriched delta(15)N values (> 6 parts per thousand). Vegetation in areas affected by rabbits had lower delta(15)N values (mean = 1.2 parts per thousand), while the highly depleted delta(15)N values (below -5 parts per thousand) of plants at upland plateau sites inland of penguin colonies, suggested that a portion of their nitrogen is derived from ammonia (mean N-15 = -10 parts per thousand) lost during the degradation of penguin guano. Vegetation in a remote area had delta(15)N values near -2 parts per thousand. These results contrast with arctic and subarctic studies that attribute large variations in plant N-15 values to nitrogen partitioning in nitrogen-limited environments. Here, plant N-15 reflects the N-15 Of the likely nitrogen sources utilised by plants.

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Several unknown, abundant brominated compounds (BCs) were recently detected in the blubber of dolphins and other marine mammals from Queensland (northeast Australia). The BC were interpreted as potential natural products due to the lack of anthropogenic sources for these compounds. This study investigated whether some of the BCs accumulated by diverse marine mammal species are identical with natural BCs previously isolated from sponges (Dysidea sp.) living in the same habitat. Isolates from sponges and mollusks (Asteronotus cespitosus) were compared with the signals detected in the mammals' tissue. Mass spectra and gas chromatography retention times on four different capillary columns of the isolates from sponges and mammals were identical in all respects. This proves that the chemical name of the compound previously labeled BC-2 is 4,6-dibromo-2-(2'-dibromo)phenoxyanisole and that the chemical name of BC-11 is 3,5-dibromo-2-(3',5'-dibromo-2'-methoxy)phenoxyanisole. Using a quantitative reference solution of BC-2, we established that the concentrations of the brominated metabolies found in the marine mammals are frequently >1 mg/kg. The highest concentration (3.8 mg/kg), found in a sample of pygmy sperm whale (Kogia breviceps), indicates that BC-2 is a bioaccumulative, natural organohalogen compound. This is supported by the concentrations of the BCs in our samples being equal to the highest concentrations of anthropogenic BCs in any environmental sample. The quantitative determination of BC-2 in blubber of marine mammals from Africa and the Antarctic suggests that BC-2 is wide-spread. These results are direct proof that marine biota can produce persistent organic chemicals that accumulate to substantial concentrations in higher trophic organisms.

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Dissertação de mestrado em Ecologia

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Dissertação de mestrado em Ecologia

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Dissertação de mestrado em Ecologia