The diet of breeding white-chinned petrels was studied during the summers of 1996 and 1998 at South Georgia. Krill abundance/availability was high throughout 1996 but apparently low at the beginning of the 1998 breeding season. The diet of white-chinned petrels was similar between years and consistent with previous studies. Krill Euphausia superba (41–42% by weight) was the single most important prey item followed by fish (39–29%) and squid (19–25%). Meal mass was consistent (110 g in 1996, 119 g in 1998) between years but a significant decrease (46%) in feeding frequency in 1998 (0.54 meals day−1 compared to 0.75 meals day−1 in 1996) resulted in 19% less food delivered to chicks in 1998 than in 1996. Breeding success, however, was consistent between years at 44% and similar to that recorded previously at Bird Island. This is in contrast to black-browed and grey-headed albatrosses, both of which experienced almost total breeding failure in 1998. It is suggested that their varied and versatile feeding methods, together with their greater diving ability, capacity to feed at night and extensive foraging range, help white-chinned petrels minimise the effects of krill shortage.

The density of nests of the magpie goose Anseranas semipalmata on the Mary River floodplain fluctuated markedly during 1988–93, failing almost completely in unfavourable (El Niño) years. Nest density and timing of nesting were strongly correlated with variations in the time of onset of the wet season, but were much less sensitive to rainfall quanta in the mid- to late wet season. Nest densities were higher and nesting was initiated earlier in breeding seasons preceded by sustained rainfalls during the transition from dry to wet seasons. Clutch sizes were slightly larger in years of early wet-season onset. Within seasons, later clutches contained fewer eggs and the eggs were smaller, probably as a consequence of later nesting by younger birds. Second clutches from a small sample of marked re-nesting birds and a pulse of nesting after flooding losses, contained similar numbers of eggs to first clutches, but the eggs were larger. Dependence of nesting on events occurring months before clutch initiation, when birds are using habitats distant from nesting colonies, illustrates the importance of integrated management of floodplain systems to meet year-round habitat needs, and the risks posed by homogenization of wetlands by improvement of pasture for grazing.

The epidemiology of the sucking lice Echinophthirius horridus was studied over a 4 year period in which their harbour seal hosts experienced marked inter-annual changes in food availability. Prevalence and intensity of infection varied in relation to host age but not sex. Burdens were highest on immature seals, but both prevalence and intensity of infection were significantly higher in years when food availability was low. Observed intra-population variations in ectoparasite dynamics suggested that reported geographical differences in the prevalence of E. horridus may have resulted from methodological differences. In contrast to previous studies of other pinnipeds, lice were also absent on weaned pups, suggesting that E. horridus is transferred horizontally. No significant differences were found in the haematological parameters of infected and uninfected hosts. Nevertheless, there was a significant negative correlation between intensity of infection and several erythrocyte parameters, suggesting that high burdens of lice may compromise diving ability.