The breeding biologies of the Sooty Albatrosses Phoebetria fusca and P. palpebrata

Abstract

The breeding biologies of the Sooty Albatross Phoebetria fusca and the Light-mantled Sooty Albatross P. palpebrata were studied at Marion Island (46°54′S, 37°4.5′E), Prince Edward group of islands, one of only two (possibly three) groups where they breed sympatrically. Phoebetria fusca is far more abundant than P. palpebrata at Marion Island.

The breeding biologies of the two species were similar; the pre-egg, egg and nestling periods of the breeding cycle are compared. There is an overlap in selection of nest sites but interspecific competition for nest sites is probably not sufficiently intense to limit either species. Giant-petrels Macronectes may be important predators of nestlings, specially those of fusca.

Differences in the pelagic distribution of the two albatrosses and in the composition of their cephalopod prey suggests that palpebrata feeds mainly south of the Antarctic Convergence and thus has farther to fly to obtain food than fusca because the Antarctic Convergence lies south of Marion Island. Interspecific differences in shifts of brooding and incubation may be related to the greater distance that palpebrata must fly to obtain food.

Elsewhere the nestling period of palpebrata is shorter than that of fusca. This is discussed in relation to the availability of food to the two species according to season. Phoebetria palpebrata may have difficulty supplying the nestling with sufficient energy to fledge, at least partly because palpebrata must fly farther than fusca to obtain food.