Figure 1 from Pérez-Rodríguez L et al., 2013.
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.
Source:
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
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I've been absent for some time, but now I remember why I used to love this web site. Thanks, I will try and check back more frequently. How frequently you update your website?
I find this extremely interesting. Did they mention if the feather pattern appears on both females and males? I feel like the real question is how is this relevant in respect to evolution? Perhaps it is a sign of how healthy and fit a potential mate is? A poor ability to gather food (whether it be from a poor foraging skill or other factors that make the individual unfit) would cause a decrease in weight (how long would the bird last in unfit conditions where food is no longer readily available?). This in turn would cause a decrease in the immune system (can this bird fight of an infection or sickness?) since the bird is not receiving enough essential nutrients. If all of this causes an outward sign, the birds that are doing poorly may not be able to find a mate, would not reproduce, and evolution would remove these individuals from the gene pool.
Appearance has always been great part of courtship in birds. I personally have worked with wild birds most of my life and fellow birding and wild bird guide writer Melissa Mayntz agrees: "...elaborate displays of prominent feathers, skin sacs or body shape can show off how strong and healthy a bird is, advertising its suitability as a mate". (http://birding.about.com/od/birdingbasics/a/courtshipbehavior.htm)
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