Table 2.

Model predictions for the allometric relationship between parent mass (M, g) and the thermal properties and dimensions of a hemispherical object according to y = aMb for heat loss, isometric and structural scaling, and tests for significant differences between actual scaling exponents (table 1) and predictions. Nest thermal properties model output values represent the exponent (slope, b) of the regression mean according to the allometric relationship y = aMb. The scaling exponent values represent the mean for all masses. Accompanying statistics include the F-ratio and p-value (the statistical probability of rejecting the null hypothesis (p > F)) for the ANCOVA comparisons between the model predictions and real nest data. n = 117 and d.f. = 1,113 for all comparisons, except nest mass, which has n = 108 and d.f. = 1,104. The replicate for the nest mass measurements is lower as some nests were excluded from analysis owing to the attachment of supporting branches.

nest parametersheat loss scalingisometric scalingstructural scaling
internal diameter (dI, cm)M0.33, F = 7.41, p = 0.01aM0.33, F = 7.41, p = 0.01aM0.33, F = 7.41, p = 0.01a
external diameter (dE, cm)M0.30, F = 65.18, p < 0.001aM0.33, F = 34.48, p < 0.001aM0.43, F = 1.37, p = 0.24
internal height (hI, cm)M0.33, F = 16.69, p < 0.001aM0.33, F = 16.69, p < 0.001aM0.33, F = 16.69, p < 0.001a
external height (hE, cm)M0.30, F = 0.63, p = 0.43M0.33, F = 0.20, p = 0.66M0.43, F = 18.94, p < 0.001a
thickness (X, cm)M0.15, F = 62.58, p < 0.001aM0.33, F = 13.92, p < 0.001aM0.52, F = 0.40, p = 0.53
surface area (A, cm2)M0.64, F = 4.80, p = 0.03aM0.67, F = 0.57, p = 0.45M0.77, F = 14.25, p < 0.001a
volume (V, ml) or mass (MN, g)M0.78, F = 33.94, p < 0.001aM1, F = 13.41, p < 0.001aM1.33, F = 0.09, p = 0.76
total nest conductance (G, mW °C−1)M0.48, F = 99.12, p < 0.001aM0.33, F = 13.36, p < 0.001aM0.25, F = 0.01, p = 0.92
  • aIndicates that the scaling exponent for the model output and real nest data are statistically different at the specified alpha value (α = 0.05) following Bonferroni adjustment.