Variation In Daily Energy Expenditure Research Articles

Intraspecies variation in avian energy expenditure: correlates and constraints

Data on energy expenditure by 553 individuals of 28 species of small bird (10–150 g) are presented. All estimates of energy expenditure were obtained using the doubly‐labelled water technique. Intraspecies variation in daily energy expenditure was found to be positively correlated with brood provisioning rates, percentage of time flying and the frequency of non‐resting activity. Correlations were also shown with body‐mass, body‐size and several environmental factors. Published data on basal metabolic rates (BMR) sometimes differed substantially from estimates either made specifically as part of the studies considered here or calculated from allometric equations. For the purpose of interspecific comparisons, specific estimates of BMR are to be preferred. When expressed as a function of BMR, energy expenditures of free‐living birds ranged from 1 + to 7 + times BMR with a mode at 3 +. Values of daily energy expenditure exceeding 4 times BMR were found in up to 48% of species and 30% of individuals, so that, contrary to earlier suggestions, 4 times BMR is not a universal upper limit to the sustained work rate of small birds. Observed upper limits tended to be higher in species with energy‐expensive foraging habits. Energy expended by breeding birds is likely to involve a balance between the benefits a greater expenditure has for offspring production and any fitness penalty associated with the high level of energy expediture which nest provisioning involves.

Effects of Carrying Radio Transmitters on Energy Expenditure of Pacific Black Brant

We compared daily energy expenditure and body mass changes of captive yearling black brant (Branta bernicla nigricans) with and without backpack-mounted radio transmitters in a repeated measures design. Daily energy expenditure was estimated by continuously monitoring 0, consumption and CO2 production for 24 hours. Carrying transmitters had no effect on daily energy expenditure (P > 0.10) or mass loss (P > 0.3). We detected no temporal variation in daily energy expenditure after attachment of transmitters, an indication that any acclimation occurred within the first 24 hours. Because experimental birds were confined to a small (45 x 60 x 74 cm) chamber during metabolism measurements, our results do not address the influence of transmitters on the cost of locomotion. J. WILDL. MANAGE. 54(1):42-45 Radio telemetry has played a significant role in studies of waterfowl movements (Ringelman and Longcore 1982) and of mortality (Ball et al. 1975). However, results of studies relying on radio telemetry may be biased if the radio packages influence the individuals carrying them. Changes in waterfowl behavior have been associated with the application of radio packages (Gilmer et al. 1974), and Gilmer et al. (1974) detected an increased recovery rate for birds carrying radios compared to normally banded controls. However, Gilmer et al. (1974) could not separate the effects of harvest rate from a potentially higher reporting rate for radiomarked birds. Survival rate may be affected by application of radio packages if the energy budgets of marked individuals are sufficiently altered by the packages and harnesses. Such changes in energy budgets could result from behavioral changes (e.g., time spent feeding), changes in the costs of locomotion, including work required to carry the mass of the radio packages, or changes in metabolism associated with the stress of carrying a radio package. For example, birds secrete corticosterone in response to short term stressors, such as handling (Wingfield et al. 1982), and chronic factors such as social environment or climate (Assenmacher 1973, Wingfield et al. 1982). Corticosterone has a marked influence on metabolism (Assenmacher 1973) and, therefore, potentially on energy balance. No study has assessed the impact of carrying radio transmitters on daily energy expenditure of waterfowl. We had 2 goals: (1) assess whether attachment of backpack-mounted radio transmitters increased metabolic rate, and (2) determine whether black brant acclimated after attachment of transmitters, causing a temporal pattern in metabolic rate. To achieve our goals, metabolic rate was monitored periodically before application of radio transmitters and from 1 to 35 days after attachment. Our study does not address changes in energy expenditure associated with increased locomotory costs (Gessaman and Nagy 1988) in free-living black brant because our measurements were made on brant confined to metabolism cages. Black brant were reared in their natal areas during studies supported by the Alaska Fish and Wildlife Research Center and Yukon Delta National Wildlife Refuge, U.S. Fish and Wildlife Service. We thank M. R. Peterson, P. L. Flint, and K. Laing for assistance in rearing goslings in the field. N. A. Gundlach assisted with maintenance of brant in Fairbanks. K. J. Kokjer provided essential help with the maintenance of the data acquisition system. M. C. Perry, K. L. Parker, and K. J. Reinecke provided very constructive comments on the manuscript. Funding was provided by the Alaska Fish and Wildlife

Variation in Daily Energy Expenditure in Nesting Northern Wheatears (Oenanthe oenanthe)

Variation in Daily Energy Expenditure in Nesting Northern Wheatears (Oenanthe oenanthe)