Phylogenetic path analysis
Two path models were strongly favored by information theory analyses, with roughly equivalent CICc values. These were models 2 and 3 (fig. 4), both of which proposed that prealternate molt and foraging stratum are direct parent variables of seasonal dichromatism and that migration distance is a direct parent of variable of day length, and only differed in whether migration distance or day length was a direct parent of prealternate molt. The best model that proposed a conditional independency for prealternate molt was model 5, the next best model after models 2 and 3, though this model showed a marked jump in its CICc value compared to models 2 and 3. (fig. S2).