A new study shows that the feather pattern on the chests of some birds (i.e. the bib) may be an outward sign of how healthy the bird is. The pattern the study refers to is called a fractal dimension, which is used to describe the complexity of the pattern (see image above). Researchers, Pérez-Rodríguez et al., discovered that red-legged partridges (Alectoris rufa) who were well-fed had more complex patterns than those who were food-restricted. Moreover, food-restricted animals weighed 13% less and had weaker immune systems.
Pérez-Rodríguez L, Jovani R, Mougeot F. Fractal geometry of a complex plumage trait reveals bird’s quality. Proc. R. Soc. B. 280(1755), 2013. doi: 10.1098/rspb.2012.2783