Biometrics, activity and energetics in different foraging environments
| Foraging conditions | ||||||
|---|---|---|---|---|---|---|
| Rich | Intermediate | Poor | Treatment | Time | Order | |
| Mass and flight muscle | ||||||
| Body mass (g) | 79.8±2.4 | 72.7±2.1 | 64.2±1.4 | F1,12=104, P<0.001 | −*** | ns |
| Muscle depression (mm) | 2.31±0.24 | 3.21±0.17 | 3.39±0.25 | F1,12=18.0, P<0.005 | ns | ns |
| Activity | ||||||
| Travel distance (km day−1) | 7.84±0.38 | 20.38±2.16 | 31.84±2.74 | F1,12=97.1, P<0.001 | ns | ns |
| Flight time (min day−1) | 32.2±2.1 | 85.4±9.3 | 136.1±12.8 | F1,12=95.8, P<0.001 | ns | ns |
| Flight speed (m s−1) | 4.08±0.08 | 3.92±0.09 | F1,202=17.6, P<0.001 | +* | ns | |
| Measured energetics | ||||||
| Assimilation efficiency | 0.826±0.010 | 0.843±0.014 | 0.840±0.016 | F1,12=2.76, P=0.12 | +** | ns |
| MEI (kJ day−1) | 149.8±5.6 | 189.2±20.3 | 215.5±9.5 | F1,12=14.4, P<0.005 | ns | ns |
| DEE (kJ day−1) | 153.8±5.1 | 192.3±16.2 | 220.2±10.1 | F1,12=22.9, P<0.001 | ns | ns |
| Enight (kJ day−1) | 37.79±1.01 | 31.92±1.22 | 27.54±1.17 | F1,12=65.8, P<0.001 | ns | ns |
| BMR (W) | 0.861±0.019 | 0.776±0.019 | 0.692±0.029 | F1,12=53.3, P<0.001 | ns | ns |
| BMRms (mW g−1) | 10.85±0.40 | 10.69±0.27 | 10.76±0.28 | F2112=0.03, P=0.88 | ns | +* |
Values are means ± s.e.m. (N=7 birds).
MEI, metabolisable energy intake; DEE, daily energy expenditure; E energy expended; BMRms, mass-specific BMR.
Flight speed was only measured in the poor and rich environment.
Test statistics are from GLMMs with bird identity as a random effect (see Materials and methods). `Time' is time elapsed since the start of the experiments and `order' is whether the first measurements were in the poor or rich environment (`+' indicates higher values in rich environment). ns, P>0.05, *P<0.05, **P<0.01, ***P<0.001.