DIETARY SEGREGATION OF KRILL-EATING SOUTH GEORGIA SEABIRDS

Citation
Jp. Croxall et al., DIETARY SEGREGATION OF KRILL-EATING SOUTH GEORGIA SEABIRDS, Journal of zoology, 242, 1997, pp. 531-556
Citations number
68
Categorie Soggetti
Zoology
Journal title
ISSN journal
09528369
Volume
242
Year of publication
1997
Part
3
Pages
531 - 556
Database
ISI
SICI code
0952-8369(1997)242:<531:DSOKSG>2.0.ZU;2-W
Abstract
The diets of six of the main seabird species (two petrels, two albatro sses, two penguins) breeding at Bird Island, South Georgia were studie d simultaneously during the chick-rearing period in 1986. For five spe cies, Antarctic krill Euphausia superba was the main food (39-98% by m ass); grey-headed albatrosses took mainly the ommastrephid squid Marti alia hyadesi (71%) and only 16% krill. The size of the krill taken was similar between seabird species, although there were small but signif icant differences between penguins and the other species. Sex and repr oductive status of krill, however, was different between all seabird s pecies, reflecting some combination of differences in foraging ranges, selectivity by predators, or differences in escape responses of krill . For the krill-eating species, the rest of the diet varied substantia lly between species, comprising Martialia and nototheniid fish (black browed albatross and, along with lanternfish, white-chinned petrel), l anternfish and amphipods (Antarctic prion and macaroni penguin), and i cefish (gentoo penguin). Long-term data on breeding success and inform ation on diet in 5-10 other years suggest that in 1986 seabird diet an d reproductive performance was indicative of a year of good availabili ty of krill around South Georgia. In such circumstances, ecological se gregation between krill-eating species appears to be maintained chiefl y by differences in foraging range and feeding methods, which are revi ewed. This situation is rather different from the few studies of seabi rd communities elsewhere, where prey type and size are believed to be the main mechanisms of dietary segregation.