A comprehensive isotopic investigation of habitat preferences in nonbreeding albatrosses from the Southern Ocean

Abstract

International audienceAlbatrosses are among the world's most endangered seabirds. Threats during the nonbreeding period have major impacts on their population dynamics, but for most species, detailed information on distribution and ecology remains essentially unknown. We used stable isotope values (δ13C and δ15N) in feathers to infer and compare the moulting (nonbreeding) habitats of 35 populations that include all the 20 species and subspecies (444 individuals) of albatrosses breeding within the Southern Ocean and in fringing subtropical waters. Isotopic values together with a review of available information show that the 20 albatrosses can be categorized into three groups depending on their favoured moulting grounds: 12 (60%) taxa forage primarily in warm neritic waters, six (30%) in northern oceanic waters and two (10%) in oceanic waters of the Southern Ocean. Stable isotopes indicate that habitat preferences during the nonbreeding period vary much less among different breeding populations in some species (wandering, Salvin's, grey-headed and light-mantled sooty albatrosses), than others (black-browed, Indian yellow-nosed and sooty albatrosses). The major finding of our isotopic investigation is that the great majority of albatrosses spend the nonbreeding period outside the Southern Ocean, with only three species (and in the sooty albatross, just one of the breeding populations) favouring oceanic subantarctic waters at that time. Hence, the study highlights the overwhelming importance of subtropical waters for albatrosses, where the birds are known to interact with human activities and are more likely to be negatively affected by the diverse range of fisheries operating in both neritic and oceanic waters

Differences in the timing and extent of annual moult of black-browed albatrosses Thalassarche melanophris living in contrasting environments

“…The general conclusion that can be taken from the bibliography that albatrosses do not moult during breeding (e.g. Cherel et al 2013) does not apply to the two populations of blackbrowed albatrosses studied here. In the Falklands, moulting of primaries, tail feathers and body feathers during the breeding season is common.…”

“…The only study reporting the regular moult of flight feathers during breeding involved yellownosed albatrosses Thalassarche chlororhynchos and found less than 10 % of the individuals still growing the last of the moulted primaries ([90 % growth completed) at the start of the incubation (Furness 1988). The chemical analysis of albatross feathers is therefore used regularly to obtain information believed to pertain to the nonbreeding period (Cherel et al 2000(Cherel et al , 2013Phillips et al 2009Phillips et al , 2011. During a long-term demographic and ecological study of black-browed albatrosses Thalassarche melanophris in the Falkland Islands (Catry et al 2010Granadeiro et al 2011), we noted the occurrence of moult of feathers of different types in the breeding colony.…”

Combined stomach content, lipid and stable isotope analyses reveal spatial and trophic partitioning among three sympatric albatrosses from the Southern Ocean

“…During the interbreeding (moulting) period, feather δ 13 C values of adult GHA were remarkably similar in all localities and years so far investigated, with birds foraging primarily in subantarctic waters (Anderson et al 2009, Cherel et al 2013. Results are more variable for the 2 Phoebetria albatrosses.…”

“…Cherel & Hobson 2007, Jaeger et al 2010b. Foraging during the interbreeding period of albatrosses can thus be examined through the stable isotope carbon signatures of their feathers , Cherel et al 2013.…”

“…Results are more variable for the 2 Phoebetria albatrosses. Depending on localities and years, feather δ 13 C values of LMSA ranged from −19.5 to −21.2 ‰, with very large variances (Jaeger et al 2010a, Cherel et al 2013, this study), except at South Georgia ). The low standard deviation at the latter locality is likely the result of measuring stable isotopes on a pool of body feathers instead of a single feather, thus blurring any intraindividual variation (Jaeger et al 2010a).…”