Basal metabolic rate in migratory waders:: intra-individual, intraspecific, interspecific and seasonal variation

1. Basal metabolic rates (BMR) were measured in 36 adult and 119 juvenile waders of 19 species on autumn migration in southern Sweden. 2. Ina comparison with literature data, it was found that juvenile BMR was generally lower than at the onset of migration in the Arctic and slightly higher than on African wintering grounds. 3. The seasonal differences may reflect local physiological adaptations or possibly a gradual decline from high premigratory levels due to growth. Our data contradict the idea that BMR is high during migration as an adaptation to generally high levels of energy expenditure. 4. The allometric exponent, scaling BMR to body mass, was significantly higher within individuals (1.19) and within species (1.82) than among species (0.62). 5. The high intra-individual exponent indicates that non-fat tissues, with a high metabolic activity, are involved in the mass changes during migratory stopover. 6. The high intraspecific exponent indicates that tissues with a high metabolic activity contributed disproportionately to variation in body mass among individuals or that larger individuals had elevated mass specific metabolic rates of some tissues.