FIGURE 5 AVONET presents raw morphological data for 90,020 in AVONET: morphological, ecological and geographical data for all birds

FIGURE 5 AVONET presents raw morphological data for 90,020 individual birds at an average of 8.1–9.0 individuals per species (varying by taxonomy), providing a foundation for a new generation of studies investigating or accounting for intraspecific variance. This figure illustrates how variance is partitioned for a key morphological trait (beak length). Left-hand panels show that most variance is explained at higher taxonomic levels (orders, family and species), whereas intraspecific (individual) variation is contrastingly low, supporting the use of species averages in comparative studies. Curves are normal distributions based on SD; percentages (%) show proportion of variance at each level. Right-hand panels show beak length variance within families and within species (restricting to families with>5 species and species with>5 individuals measured; note different axis scales in upper and lower panel). Sequential ranks show a 'hockey-stick' distribution with examples of the most extreme outlier family (Scolopacidae) illustrated. Extreme within-species values for beak variance may reflect polymorphism or, in some cases, measurement error