Plumage ornamentation as a potential driver of behavioral differences in a dichromatic passerine

In sexually dimorphic species, energetically demanding traits can serve as an honest sexual signal, benefiting males with increased ornamentation. Although possibly a survival handicap, ornamentation may improve fitness by increasing reproductive opportunities. Conversely, conspicuous colorations may improve fitness if, by openly conveying that the individual is a difficult food source, they improve survival. It follows that exaggerated ornamentation may create selective pressures that affect the two phenotypes differently. Therefore, it can be predicted individuals of polymorphic species may show intra-species behavioral differences (predator avoidance, niche partitioning, grouping) to match their phenotypes. In this study we examined whether the ornamentation of male red-backed fairywrens (Malurus melanocephalus) was related to an increase in certain behaviors. We conducted focal observations (n=276) on bright (n=8) and cryptic males (n=55) during the nonbreeding season to compare basal behavioral differences. We found that bright plumage was related to increases in the time spent preening (12.1 ± 2.7 s), allo-preening (5.7 ± 1.6 s), courtship displays (8.1 ± 1.6 s), flying (2.5 ± 0.8 s), and sitting (11.1 ± 5.1 s). Of these five statistically significant results, three seem to be more biologically significant when extrapolated to a daily time allocation. Bright males spent 58, 53, and 39 minutes more than dull males per day preening, sitting, or displaying, respectively, but only 27 and 12 minutes/day moreallo-preening and flying. Preening and displaying have a direct connection to mate attraction, supporting the idea that exaggerated ornamentation positively alters sexual behaviors rather than vigilance or anti-predatory behavior.