Table 4. Linear regression results.

	Categories included	N	Slope	Intercept	R2	PPE naive	PPE corr.
A	Columbidae (closest relatives)	16	2.9462	−0.7754	0.796	30.1	28.3
B	Galloanserae and Tinamiformes (heavy-bodied)	19	2.4414	−0.1412	0.933	18.1	18.1
C*	Ratites (flightless)	18	2.67942	−0.63748	0.985	12.5	11.3
D	Columbidae, Galloanserae and Tinamiformes	35	2.5660	−0.2978	0.871	25.2	24.5
E*	Columbidae, Ratites	34	2.4241	−0.1313	0.974	26.5	25.7
F	Galloanserae and Tinamiformes, Ratites	37	2.42748	−0.14354	0.985	18.3	18.2
G	Columbidae, Galloanserae and Tinamiformes, Ratites	53	2.41731	−0.11616	0.974	23.3	22.9

Notes:

Results of the linear regression lines for log femur circumference (mm) against log body mass (g) for various combinations of bird groups. Columbidae are the closest living relatives, Galloanserae and Tinamiformes are medium-sized ground-dwelling birds and Ratites are flightless. The letters correspond to those in Fig. 2. Percent prediction error (PPE) for the naive estimate are given in addition to the coefficient of variation (R²). Categories with an * were corrected using the ratio estimator, all other categories using the smearing coefficient.