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First published online October 7, 2004
Journal of Experimental Biology 207, 3977-3984 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01235

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The energetic cost of variations in wing span and wing asymmetry in the zebra finch Taeniopygia guttata

C. Hambly^1,*, E. J. Harper² and J. R. Speakman^1,3

¹ Aberdeen Centre for Energy Regulation and Obesity, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, Scotland, UK
² The Waltham Centre for Pet Nutrition, Waltham-on-the-Wolds, Leicestershire, LE14 4RT, England, UK
³ Aberdeen Centre for Energy Regulation and Obesity, Division of Energy Balance and Obesity, Rowett Research Institute, Bucksburn, Aberdeen AB21 9BS, Scotland, UK

View larger version (12K): [in a new window]   Fig. 1. Typical isotope enrichments from breath samples taken before (diamonds) and after flight (circles) in a zebra finch. In this example, depressed isotope enrichment occurred in the first breath sample collected at 3 min after flight. A linear regression was therefore fitted before flight and forward-extrapolated to predict the enrichment at the time when the bird first began to fly. A polynomial regression was fitted after flight and back-extrapolated to predict the enrichment at the time when flight ended (accounting for the time spent on the perches). This generated two points, the gradient between them being the elimination rate (kc) during flight. kc was substituted into Equations 1 and 2, to give predictions of O2 and CO2, which were converted to energy expenditure in W.

View larger version (15K): [in a new window]   Fig. 2. Relationship between flight cost and (A) body mass (y=4.86–0.21x, r2=0.11), (B) wing amplitude y=5.45–0.029x, r2=0.13) and (C) wingspan (y=0.25x–2.66, r2=0.09), which were the only parameters that had a significant influence on flight cost.

View larger version (12K): [in a new window]   Fig. 3. The mean difference in flight cost (W) between birds with trimmed wings, and the pre-manipulated flight cost for each individual. *Increase in flight cost was significantly higher than in the pre-manipulated individuals. Values are means ± S.E.M. For N values, see Table 1.

View larger version (13K): [in a new window]   Fig. 4. The difference in mean wing beat frequency (Fb) between pre- and post-manipulated birds (beats s–1). The largest increase in Fb from pre-manipulated levels occurs between the birds that had 1.0 cmremoved from one wing. *Increase in Fb was significantly higher than in the pre-manipulated individuals. Values are means ± S.E.M. For N values, see Table 1.

View larger version (13K): [in a new window]   Fig. 5. Difference in mean wing amplitude between pre- and post-manipulated birds. In manipulated birds, left or right wings were trimmed, by 0.25, 0.5 or 1.0 cm. Asterisks indicate where the resulting increase in wing beat frequency Fb was significantly higher than the pre-manipulated individuals. Values are means ± S.E.M. For N values, see Table 1.

View larger version (23K): [in a new window]   Fig. 6. Differences in mean up- and downwing stroke duration between pre- and post-manipulated birds. Asterisks indicate where the resulting increase in wing beat frequency Fb was significantly higher than the pre-manipulated individuals. Values are means ± S.E.M. For N values, see Table 1.

View larger version (13K): [in a new window]   Fig. 7. The difference in the mean flight speed (m s–1) with each manipulation compared to the pre-manipulated flight speed. There was a slight but not significant increase in flight speed between the manipulations when one wing only was trimmed. When both wings were trimmed there was a significant decrease in flight speed. *, P=0.02.