The Energetic Cost of Feather Synthesis Is Proportional to Basal Metabolic Rate

Serge Daan Feather production costs (Cf ; kJ g 01 dry feathers) did not Physiological Zoology 66:490–510 (1993) differ significantly between bluethroat individuals (F5, 18Å 1.08, P Å 0.41; common slope, 341 { 55 [SE] kJ g01 dry feathers, F1, 23 Å 38.5, r 2 Å 0.72, P õ 0.001) or redpoll individuals (F4, 15 Å 1.0, P Å 0.43; common slope, 163 { 45 [SE] kJ g01 Because of a calculation error, we presented erroneous data dry feathers, F1, 19Å 13.0, r Å 0.48, Põ 0.002). The Cf differed on energetic costs of feather production in two passerine spebetween species, being significantly higher in the bluethroat cies: the bluethroat, Luscinia s. svecica, and the common red(ANCOVA, F1, 51 Å 34.4, P õ 0.001). Assuming an energy poll, Carduelis f. flammea. content of 22 kJ g01 dry feathers, the efficiencies of producing The corrected premolt basal metabolic rate (BMR) in bluefeathers were 6.5% for bluethroats and 13.5% for redpolls. throats averaged 22.3 kJ d01 (SD Å 3.5). During peak molt, With the new values the relationship between log Cf and log average metabolic rate was 41.3 kJ d01 (SD Å 6.5). The correbody mass was not significant: log Cf Å 2.016 0 0.225 log sponding values for redpolls were 20.8 kJ d01 (SD Å 2.9) and body mass (F1, 5 Å 4.77, SE of the slope Å 0.103, r 2 Å 0.49, 28.1 kJ d01 (SD Å 4.1), respectively. Postmolt BMR averaged P õ 0.081). However, there was a significant relationship be35% higher and 1% lower than premolt BMR in bluethroat tween log Cf and log mass-specific BMR: log CfÅ 2.330/ 0.585 and redpoll, respectively. The difference in metabolic rate belog mass-specific BMR (F1, 5 Å 9.91, SE of the slope Å 0.185, tween the five molt stages, tested with repeated-measures analyr 2 Å 0.66, P õ 0.025). Thus, the relationship between Cf and sis, were: for bluethroats, F4, 20Å 22.33, Põ 0.001; for redpolls, mass-specific BMR holds, as originally suggested, although the F4, 16 Å 10.74, P õ 0.001. The patterns differed significantly relationship is not directly proportional. between species (species 1 stage: F4, 36 Å 7.48, P õ 0.001),