Molt and dichromatism scoring
We scored the extent of prealternate molt and plumage dichromatism using
a combination of specimen examinations and literature review. All
specimens were examined at the LSU Museum of Natural Science. We used a
combination of collection date, data from specimen labels, and known
molt patterns (Pyle 2007) to classify individuals by age, sex, and molt
stage. Species or life stages not available at the LSUMNS were scored
from the literature (Pyle 2007) or visual examination of published
photographs of plumages (Dunn and Garrett 1997, Stephenson and Whittle
2013). We defined a dichromatic region as a region with visible color or
pattern differences between basic and alternate plumage. We scored
dichromatism in feather regions as follows: 1 = region completely
dichromatic, 0 = no dichromatism in region, and 0.5 = and partial
dichromatism or intraspecific variation. In some species, extent of molt
and dichromatism differs between the first prealternate molt and
definitive prealternate molts. In these cases, we considered only the
definitive prealternate molts (Wolfe et al. 2014). We scored molt extent
using the same museum and literature resources, through examination of
molt limits (Pyle 1997a). For each body region (Fig 2f), we scored molt
as follows: 1= complete replacement of the feathers in the region, 0 =
molt absent from the region, and 0.5 = either partial replacement of the
feathers in that region, or intraspecific variation in extent of molt.