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Marine Ecology Progress Series

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MEPS 228:263-281 (2002)  -  doi:10.3354/meps228263

Food and feeding ecology of the sympatric thin-billed Pachyptila belcheri and Antarctic P. desolata prions at Iles Kerguelen, Southern Indian Ocean

Yves Cherel1,*, Pierrick Bocher1,2, Claude De Broyer3, Keith A. Hobson4

1Centre d¹Etudes Biologiques de Chizé, UPR 1934 du Centre National de la Recherche Scientifique, BP 14, 79360 Villiers-en-Bois, France
2Laboratoire de Biologie et Environnement Marins, EA 1220 de l¹Université de La Rochelle, 17026 La Rochelle Cedex, France
3Institut Royal des Sciences Naturelles de Belgique, Département des Invertébrés, 29 rue Vautier, 1000 Brussels, Belgium
4Prairie and Northern Wildlife Research Centre, Environment Canada, Saskatchewan S7N 0X4, Canada

ABSTRACT: The food and feeding ecology of the 2 closely related species of prions Pachyptila belcheri and P. desolata was investigated over 3 consecutive chick-rearing periods at Iles Kerguelen, the only place where they nest sympatrically in large numbers. In all years, the 2 prion species fed on crustaceans, with a small proportion of mesopelagic fish and squid. The hyperiid amphipod Themisto gaudichaudii was consistently the dominant prey item, accounting for 76 and 70% by number, and 57 and 57% by reconstituted mass of the diet of P. belcheri and P. desolata, respectively. Prions, however, were segregated by feeding on different euphausiids, P. belcheri on Thysanoessa sp. (18% by number and 16% by mass) and P. desolata on Euphausia vallentini (9% by number and 15% by mass). P. desolata also caught more small prey such as copepods (9 vs <1% by number) and cypris larvae of Lepas australis (8 vs 3% by number) than P. belcheri, which can be related to the beak filtering apparatus present only in the former species. Biogeography of the prey and their state of digestion indicate that prions foraged in a wide variety of marine habitats, including the kelp belt, kelp rafts, and coastal, neritic and oceanic waters. Noticeable is the occurrence of E. superba in a significant number of food samples (15 and 10% for P. belcheri and P. desolata, respectively), suggesting feeding in distant foraging grounds in southern Antarctic waters, >1000 km from the breeding colonies, during the chick-rearing period. The stable-carbon and -nitrogen isotopic compositions of chick feathers were identical in both species, indicating no important trophic segregation during the breeding period, when adult birds are central-place foragers. The ratios were, however, different in adult feathers, suggesting moulting in Antarctic waters for P. belcheri and in subtropical waters for P. desolata, i.e. in distinct foraging areas when birds are not constrained to return to the colonies.

KEY WORDS: Euphausia superba · Pachyptila · Petrels · Seabirds · Trophic relationships · Stable- carbon isotopes · Stable-nitrogen isotopes · Themisto gaudichaudii

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