Phylogenetic mixed models for molt and dichromatism extents
We built phylogenetic mixed models to predict the presence and extent of prealternate molt and seasonal dichromatism to understand the relative influences of life history and environmental variables on these traits. To build mixed models of exogenous correlates of molt extents, we first conducted pairwise phylogenetic generalized least squares analysis over extents of molt, dichromatism, and exogenous correlates (extended data table 1) using the package caper (Orme et al. 2013) in R. We examined pairwise PGLS results for strength and significance of interactions and used these interactions to build sets of mixed models to test for the effects of exogenous drivers on extents of molts and dichromatism by examining pairwise interaction between molts, dichromatism, and ecological data, as well as covariation between life history and ecological correlates. We evaluated these mixed models using caper, MuMIn (Barton 2016) and Nlme (Pinheiro et al. 2016) in R, and organized the models using information theory by ranking models by their AICc score (Table 1).