Fig. 1

Phylogenetic tree of 16 species built on 623 TreeFam [12] single-gene families. Branch lengths are scaled to estimate divergence times. All branches are supported by 100 bootstraps. The song bird clade is depicted in blue, Galliformes jn purple, Anseriformes in green, and nocturnal birds in red. Ratites (Struthio camelus and Apteryx mantelli) and Tinamus guttatus are highlighted in light green. The number of genes gained (+ red) and lost (− blue) is given underneath each branch. The rate of gene gain and loss for the clades derived from the most common recent ancestor was estimated [77] to 0.0007 per gene per million years