Age determination based on molt patterns and skull ossification in the blue and yellow tanager (pipraeidea bonariensis)

Abstract

We studied molt patterns and age determination based on molt limits, plumage criteria, and skull ossification for the Blue‐and‐yellow Tanager (Pipraeidea bonariensis), a passerine that is commonly distributed along the western slope of the Peruvian Andes. Through careful examination of live individuals in the hand and museum specimens, we suggest that P. bonariensis exhibits a complex alternate strategy with partial preformative and prealternate molts during its first cycle, a complete definitive prebasic molt, and presumably a partial definitive prealternate molt starting with its second cycle. We established the age in 68% of captured individuals using the skulling technique. Most individuals of P. bonariensis were recorded with fully ossified skulls during their preformative molts, whereas some adults in basic plumage had retained small, unossified windows. Our results corroborate those reported for related Neotropical taxa and provide important guidelines that facilitate an accurate and rapid technique for aging and sexing Neotropical tanagers in the hand, an essential requirement in demographic studies and long‐term banding projects.