Figure 1. Variation in the pigeon craniofacial skeleton compared to avian diversity.
a, Original examples of domesticated pigeon breed diversity from Darwin1. b, Modern examples (left) illustrate notable breed variants examined in this study (see Supplementary Fig. 1 for a complete list). Examples of pigeon breeds with extreme craniofacial shapes (right) qualitatively converge on distantly related avians. c, Examples of avian crania with shape characteristics similar to domesticated pigeon breeds (individual crania shown scaled to similar braincase length).