Phenotypic flexibility in basal metabolic rate and the changing view of avian physiological diversity: a review.

摘要: Comparative analyses of avian energetics often involve the implicit assumption that basal metabolic rate (BMR) is a fixed, taxon-specific trait. However, in most species have been investigated, BMR exhibits phenotypic flexibility and can be reversibly adjusted over short time scales. Many non-migrants adjust seasonally, with winter usually higher than summer BMR. The data are currently available do not, however, support idea magnitude direction these adjustments varies consistently body mass. Long-distance migrants exhibit large intra-annual changes BMR, reflecting physiological associated different stages their migratory cycles. Phenotypic also represents an important component short-term thermal acclimation under laboratory conditions, captive birds increasing when acclimated to low air temperatures vice versa. emerging view highly flexible trait continually response environmental factors such as temperature. within-individual variation observed demands critical re-examination approaches used for comparisons across taxa. Several key questions concerning shapes other properties reaction norms urgently need addressed, hypotheses adaptation should explicitly account flexibility.