Antarctic Science



Diet of grey-headed albatrosses at the Diego Ramírez Islands, Chile: ecological implications


JAVIER ARATA a1c1, GRAHAM ROBERTSON a2, JOSÉ VALENCIA a3, JOSÉ C. XAVIER a4 and CARLOS A. MORENO a1
a1 Instituto de Ecología y Evolución, Campus Isla Teja, Casilla 567, Universidad Austral de Chile, Valdivia, Chile
a2 Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia
a3 Instituto Antártico Chileno, Plaza Muñoz Gamero 1055, Punta Arenas, Chile
a4 British Antarctic Survey, NERC, High Cross, Madingley Road, Cambridge CB3 OET, UK

Article author query
arata j   [PubMed][Google Scholar] 
robertson g   [PubMed][Google Scholar] 
valencia j   [PubMed][Google Scholar] 
xavier jc   [PubMed][Google Scholar] 
moreno ca   [PubMed][Google Scholar] 

Abstract

The diet of grey-headed albatrosses at Diego Ramírez was analysed and compared to that of the sympatric black-browed albatross. Diet composition was inferred from an analysis of prey hard parts present in 103 chick regurgitates obtained during breeding seasons 2000, 2001 and 2002. The squid Martialia hyadesi predominated in the diet samples in 2001 and 2002 (89% and 81% of reconstituted mass), but was absent from the 2000 samples. Reconstituted mean mass per sample in 2000 was significantly lower than in 2001 and 2002. Chick growth rate during 2000 was also the lowest recorded. This suggests that M. hyadesi plays an important role in the breeding performance of grey-headed albatrosses at Diego Ramírez. Low presence of M. hyadesi in grey-headed albatrosses' diet at South Georgia in 2000, a year with significant low breeding success, suggests ocean-wide processes affecting the availability of this prey to both populations simultaneously. Overlap in diet composition, and inferred feeding areas, between the sympatric albatross species at Diego Ramírez was minimal. Grey-headed albatrosses fed mainly on species associated with the Antarctic Polar Front, whereas black-browed albatrosses consumed benthopelagic species frequently caught in fishing operations in southern Chile.

(Received July 10 2003)
(Accepted April 20 2004)


Key Words: ENSO; niche partitioning; squid; sympatry; Thalassarche chrysostoma; T. melanophrys.

Correspondence:
c1 Corresponding author: javierarata@entelchile.net


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