Secuencia de mudas y plumajes de Volatinia jacarina y Sporophila intermedia en el valle del Magdalena

Information on molt strategies is important for understanding the life history of birds but their study is still limited, hindering the comparative study of their life cycles. In order to better understand the molt strategies of the Blue-black Grassquit (Volatinia jacarina) and the Gray Seedeater (Sporophila intermedia), two common granivorous tanagers in the lowlands of northern South America, we present descriptions of the sequence of molts and plumages, at a locality in the upper Magdalena valley (Colombia), using the Wolfe-Ryder-Pyle age system based on molt cycles and supplemented with photographic material. Both V. jacarina and S. intermedia showed a Complex Alternate Strategy, consistent with that described for some other tanagers and other passerines. The prebasic molt in both species was complete, as was the performative molt, while prealternate molt was partial. The full extent of the performative molt and the presence of a prealternate molt may be associated with the habits of these species occupying open areas with high sun exposure and therefore requiring more frequent replacement of feathers. However, the prealternate molt might be associated with sexual selection processes. The sequence of molts and plumages identified 11 age classes in V. jacarina and eight in S. intermedia, involving birds in their first and second cycles and individuals in definitive molt cycles, supporting the use of WRP system, which can provide relevant information for the study of the age structure and life cycles in neotropical passerines.