Figure 4.

Factor of safety F.S., C number and the phylogenetic relationship of 18 ratite species. The phylogenetic tree was plotted with cladogram using ggtree [40,41] and the nearby graph was plotted by package ggplot2 [42]. (a) phylogeny of ratites is based on a tree of Mitchell et al. [7], and phylogeny of moa is supplemented by Bunce et al. [30]. (b) the pink bar indicates the case of incubation by females, whereas blue indicates incubation by males. The purple bar in some species indicates F.S. overlap of two sexes, whereas green indicates species with no sexual size dimorphism. (c) the C numbers for ratites were predicted by FEA simulations. See Supplementary Dataset for details on the source of bird images (Table S1).