Male red-backed fairy-wrens have two different plumage types: “bright” males with black and red plumage, and “dull” birds with brown female-like plumage. Many dull males can retain a few black or red feathers indicating their plumage prior to their last molt, thus we are able to identify their sex when we capture them. Additionally, some males can molt into an intermediate type between the two, giving them a spotty appearance. The crew this year is evenly split between designating these “spotty” males as adorable or motley.
For the most part, males molt into bright plumage prior to the breeding season, and then into dull plumage during the nonbreeding season. Since the timing of our field season falls in the nonbreeding season, most of the males on the site right now are dull. A few males were able to maintain bright plumage, perhaps indicating high androgen levels or superior physiological condition. Additionally, a handful of males are in the process of molting into bright plumage right now, which marks a very early pre-nuptial molt as they gear up for breeding. These males have also been experiencing bill darkening, a sign of social dominance or androgen levels. Notice the difference in plumage and bill color in the same bird from captures over a several week period.