Molt strategy and delayed plumage maturation in the Lined Seedeater

. Lined Seedeaters Sporophila lineola , an intra-tropical migratory songbird, exhibit extensive phenotypic variation, with characteristic black-and-white male and brownish female plumages. In this study, we investigated whether variation in male plumage represents delayed plumage maturation, as reported for many other Sporophila seedeaters. We used data on molt and plumage from a seven-year-long study of color-banded Lined Seedeaters in southeastern Brazil. We also gathered molt and plumage data from museum collections and citizen-science platforms to identify which molts occur outside the breeding grounds. Our findings show that Lined Seedeaters follow a complex basic strategy, but the possibility that some individuals exhibit a complex alternate strategy, which is a common strategy among congeners, cannot be ruled out. Preformative molt and fresh formative plumage were recorded within the breeding grounds in the last months of the breeding season. Prebasic molt also start on the breeding grounds and probably continue during migration to the wintering grounds. Observed phenotypic variation in plumage of Lined Seedeater males is a product of delayed plumage maturation. Breeding males in female-like plumage are formative individuals in their first breeding season. All monitored males acquired black-and-white definitive plumage after their first breeding season, during the second pre-basic molt, but we found limited evidence that some individuals may retain the brownish plumage for more than one cycle. Descriptions presented here advance our understanding of Sporophila molt