Unraveling a complex alternate molt strategy: more evidence for prealternate molts and alternate plumages in the Blue-and-yellow Tanager (Pipraeidea bonariensis darwinii)

Abstract

Some birds replace feathers after the formative plumage of the first cycle and after basic plumages in subsequent cycles as a consequence of prealternate molts. The presence of prealternate molts has been suggested to be due to prolonged exposure to sunlight, especially for birds inhabiting exposed and scrubby areas. Although prealternate molts appear to be common in many Nearctic-Neotropic passerines, these can be also present in resident Neotropical species. For example, prealternate molt has been reported in 14 species among nine genera in thraupids. Here, using wild individuals and museum specimens, we describe the presence of a Complex Alternate Strategy in the molt cycle of the Peru’s Blue-and-yellow Tanager (Pipraeidea bonariensis darwinii). We categorized seven molt cycle–based age groups in 75 wild-captured birds and thirteen molt cycle–based age categories across 167 museum specimens. Our results confirm the existence of limited to partial prealternate molts in Blue-and-yellow Tanager and demonstrate the importance of investigating the presence of these types of molts in wild bird populations.