OBSERVATIONS ON THE LAVA GULL LARUS FVLIGINOSUS

Abstract

SummaryLava Gulls Larus fuliginosus live as scavengers and unspecialized predators along the shores of the Galapagos Islands. Although they concentrate locally at places where refuse is available, their breeding density is low: eight breeding pairs were found along a stretch of 35 miles of the coast of Indefatigable Island. The total (world) population is likely to be less than 300–400 breeding pairs.Their low breeding density and small total population is attributed to the fact that they are confined to linear feeding grounds of limited extent, which provide a sparse food supply for much of the year.Lava Gulls nest solitarily, usually in sheltered places near coastal lagoons; all the nests found were at least two miles from any other known site. The clutch consists of two eggs, incubation (one case) lasts 32–33 days, and the fledging period is about 60 days.Breeding takes place throughout the year, with no apparent peak. Individual cycles of 9–12 months have been recorded.Observations are given on behaviour and displays, and on the sequence of plumage change and moult in the first two years of life.