Energetics of nestling growth and parental effort in Antarctic fulmarine petrels

Abstract

One of the main evolutionary options available to birds for balancing food supply and production is to vary nestling growth rate (Ricklefs et al., 1998). The consequences of growth rate variation on nestling energy requirement is complex, however, and depends upon whether one considers the total energy metabolized during growth or the energy metabolized per day. A reciprocal relationship exists between total metabolizable energy (TME) and daily metabolizable energy (DME), such that nestlings that spend longer in the nest than predicted from their mass generally have lower DME but higher TME values than nestlings that fledge sooner (Weathers, 1992(Weathers, , 1996. Consequently, although lengthening the nestling period decreases the amount of food that parents must provide their nestlings on a daily basis, it increases the total energy required per offspring and thus might negatively impact production at the population level in energy-limited environments.Antarctic fulmarine petrels are an excellent group in which to investigate linkages between nestling energetics, growth rate, and parental effort. Like other procellariiform seabirds, they exhibit a suite of life-history traits that have long been viewed as adaptations to energy limitation arising from a patchy and unpredictable food supply (Ashmole, 1971) -production of a single chick, slow growth, a long juvenile period and high adult survival (reviewed by Warham, 1990). Yet Antarctic fulmarine petrels differ from most procellariiform species in that their chicks can grow twice as fast as predicted allometrically (Warham, 1990;Hodum, 1999). Furthermore, they breed in some of the coldest conditions encountered by any bird, with air temperatures as low as -25°C (Bech et al., 1988). Relatively fast growth in a cold environment should increase nestling energy demand and concomitantly affect parental provisioning effort.In this study, we used the doubly labeled water (DLW) technique to measure adult and nestling energy requirements in four of the five fulmarine petrel species that breed in Antarctica: the Antarctic fulmar Antarctic fulmarine petrels breed in some of the coldest conditions encountered by any bird and their young grow twice as fast as predicted allometrically. To examine the energetic consequences of fast growth in a cold environment, we used the doubly labeled water technique to measure field metabolic rates of adults (three species) and different-aged nestlings (four species) of Antarctic fulmarine petrels in the Rauer Islands, East Antarctica: Antarctic fulmar Fulmarus glacialoides, Antarctic petrel Thalassoica antarctica, Cape petrel Daption capense and snow petrel Pagodroma nivea. We used our data to assess parental effort and, together with literature values on nestling growth and resting metabolic rate, to construct and partition nestling energy budgets. Nestling total energy expenditure and peak daily metabolic rate were significantly higher than predicted allometrically (33-73% and 17-66% higher, respectively), and the relative cost of grow...

Application of the two-sample doubly labelled water method alters behaviour and affects estimates of energy expenditure in black-legged kittiwakes

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Is basal metabolic rate influenced by age in a long-lived seabird, the snow petrel?

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