Figure 1
![Figure 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2F1756-0500-6-310/MediaObjects/13104_2013_Article_2332_Fig1_HTML.jpg)
Four plumage categories of the studied feral pigeons: white or almost white (pigeons that have a pure white color over almost all the body, but show a few feathers of a different color), blue bar (wild type), spread (melanic) and ash-red. The three first categories correspond to an increasing production of eumelanin, whereas the last one corresponds to a production of pheomelanin.