Table 1.

Linear mixed model (REML) of energy expenditure (from Experiment 1) in terms of food quality, temperature variation, mean temperature and time of day

Energy expenditure
Termd.f.EffectWald statistic (χ2)P value
Minimal model
    Food quality
        HQ1052.48<0.001
        LQ89.0±12.3
    Temperature treatment
        C0
        L229.7±15.014.83<0.001
        H58.2±15.2
    Mean temperature1-3.98±1.388.290.004
    Time of day
        Day1075.28<0.001
        Night-172.2±19.8
Excluded terms
    Egg mass12.820.093
    Week10.780.376
  • A random term of `bird identities and calorimeter chamber' was used (χ2=37.24; d.f.=1; P<0.001) to account for the non-independence of conditions from different chambers, and repeated measures of the same birds.

    For definitions of HQ, LQ, C, L and H, see text.