The relationship between uncinate process length (UPL) and body mass (a) species level analysis, b) comparative analysis using independent contrasts and the phylogeny of Livezey and Zusi [31].

Diving birds (grey solid triangles and grey regression lines), non-specialists (open squares and black regression lines) and walkers (solid circles and dashed regression lines). The equations describing the lines of best fit were y = 1.96 x0.35 (0.30−0.41) (t = 12.80, n = 27, r2 = 0.85, p<0.001) and y = x0.33 (0.25−0.42) (t = 8.47, n = 23, r2 = 0.68, p<0.001) for diving birds, y = 1.29 x0.34 (0.29−0.38) (t = 14.94, n = 72, r2 = 0.71, p<0.001) and y = x0.35 (0.30−0.41) (t = 12.47, n = 57, r2 = 0.63, p<0.001) for non-specialists, and y = 1.34 x0.28 (0.07−0.48) (t = 2.99, n = 13, r2 = 0.15, p<0.02) and y = x0.30 (0.12−0.49) (t = 3.57, n = 12, r2 = 0.06, p<0.005) for walkers in a & b respectively.