Variation in energy expenditure among black-legged kittiwakes: effects of activity-specific metabolic rates and activity budgets.

We sought to determine the effect of variation in time-activity budgets (TABs) and foraging behavior on energy expenditure rates of parent black-legged kittiwakes (Rissa tridactyla). We quantified TABs using direct observations of radio-tagged adults and simultaneously measured field metabolic rates (FMR) of these same individuals (n=20) using the doubly labeled water technique. Estimated metabolic rates of kittiwakes attending their brood at the nest or loafing near the colony were similar (ca. 1.3 x basal metabolic rate [BMR]), although loafing during foraging trips was more costly (2.9 x BMR). Metabolic rates during commuting flight (7.3 x BMR) and prey-searching flight (6.2 x BMR) were similar, while metabolic rates during plunge diving were much higher (ca. 47 x BMR). The proportion of the measurement interval spent foraging had a positive effect on FMR (R2=0.68), while the combined proportion of time engaged in nest attendance and loafing near the colony had a negative effect on FMR (R2=0.72). Thus, more than two-thirds of the variation in kittiwake FMR could be explained by the allocation of time among various activities. The high energetic cost of plunge diving relative to straight flight and searching flight suggests that kittiwakes can optimize their foraging strategy under conditions of low food availability by commuting long distances to feed in areas where gross foraging efficiency is high.

Gizzard nematodes of Canada geese wintering in southern Illinois.

Gizzards from 64 hunter-shot Canada geese (Branta canadensis) were collected in southern Illinois (USA) in December 1991 and January 1992 to determine the prevalence and intensity of gizzard nematodes. Three species of gizzard nematodes were recovered: Amidostomum anseris, Amidostomum spatulatum, and Epomidiostomum crami. The prevalence of infection was 98%. Mean intensity was 17.8 nematodes per host and was significantly greater for immature geese (40.3 nematodes/host) than for adult geese (10.9 nematodes/host). The intensity of both A. anseris and E. crami was greater in immature geese, but even the most heavily infected birds did not display serious lesions. Despite a dramatic increase in the population of geese, mean intensity in adult geese was similar to mean intensity reported from earlier studies at the same site. Mean intensity in immature geese in 1991 and 1992 was greater than in earlier studies.

Development of homeothermy in the diving petrels Pelecanoides urinatrix exsul and P. georgicus, and the Antarctic prion Pachyptila desolata.

Body temperatures of South Georgia diving petrel (P. georgicus) chicks increased from about 37.5 degrees C at hatching to between 38.5 and 39 degrees C within two weeks. Temperatures of common diving petrel P. u. exsul chicks averaged 38.8 degrees C after two weeks of age. Burrow temperatures varied between 5 and 10 degrees C. Measurements of oxygen consumption and body temperature indicated that chicks achieve effective endothermy at 5 degrees C after 9 days in P. u. exsul, 5-6 days in P. georgicus, and 0 days in the Antarctic prion (Pachyptila desolata). The maximum mass-specific, cold-induced oxygen consumption of small chicks that we could measure with our apparatus (ca. 5-6 cc O2/g per hr) was achieved at 5-6 days in P. u. exsul, 3 days in P. georgicus, and 0 days in P. desolata. Mass-specific thermal conductance decreased with age and body size in all 3 species, but was highest in P. u. exsul and lowest in P. desolata. Conductance was similar at the age of effective endothermy in all 3 species (ca. 3 J/g per hr per degrees C). The period required for the development of endothermy is related to age-specific changes in both conductance and capacity for heat production and it closely parallels the length of the brooding period. It is suggested that the length of the period of thermal dependence of the chick is related to the distance between feeding areas and the nesting site.