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      Metabolic costs of egg production in the European starling (Sturnus vulgaris).

      1 ,
      Physiological and biochemical zoology : PBZ
      University of Chicago Press

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          Abstract

          The energy cost of egg production in passerine birds has typically been estimated to be 45%-60% of basal metabolic rate (BMR), but this is based on theoretical models using data on energy content of eggs and reproductive tissue; there are still very few empirical data on egg production costs. In this study, we directly measured resting metabolic rate (RMR) in egg-laying female European starlings (Sturnus vulgaris) over 3 yr. We compared these data with RMR of nonbreeding and chick-rearing birds and with estimated energy expenditure generated from a typical energy content model by using empirically derived data from body composition analysis for this species. We found marked variation in RMR between years and between reproductive stages, which complicates comparisons among breeding stages for the assessment of relative egg production costs. On the basis of this method, RMR during egg laying varied from +74% to -13% of nonbreeding RMR and from +20% to -7% of chick-rearing RMR. We therefore used an alternate approach: measuring changes in RMR through the complete cycle of follicle development and ovulation. The increase in RMR from the beginning of prelaying to the six-follicle stage (before first ovulation) when birds have a complete developing follicle hierarchy was 22.4%. This value is still much lower than that estimated from our energy content model. We discuss conceptual problems associated with the theoretical energy content approach but also suggest, on the basis of earlier work done in our lab, that the measured increase in RMR might still underestimate the actual cost of egg production if birds reallocate energy between different physiological systems.

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          Author and article information

          Journal
          Physiol. Biochem. Zool.
          Physiological and biochemical zoology : PBZ
          University of Chicago Press
          1522-2152
          1522-2152
          September 27 2002
          : 75
          : 4
          Affiliations
          [1 ] Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada. fvezina@sfu.ca
          Article
          PBZ020065
          10.1086/343137
          12324894
          0c880895-6561-4983-ab9c-409e5a29c32d
          History

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