Modifications to a molt-based ageing system proposed by Wolfe et al. (2010)

Wolfe et al. (2010. Journal of Field Ornithology 81: 186194) proposed a coding system for ageing birds based on the sequence of molts and plumages, which is more practical than a calendar-based system, especially in tropical and southern latitudes where species often breed across 1 January. The WolfeRyderPyle (hereafter, WRP) three-letter system is based on recognition of molt cycle (first, second, third, definitive, and so on) and plumage phase (juvenile, supplemental, formative, alternate, and basic). For example, a bird in First Cycle Formative plumage is coded as FCF. We propose the use of two additional code options that further refine age brackets. First, we suggest the use of an after or A code in place of the C, or cycle code, where an earlier molt cycle or plumage can be ruled out. For example, a bird that exhibits Staffelmauser might be aged as after-third cycle basic, or TAB. Second, we suggest using pre or P in place of the C, or cycle code, when birds are actively molting, such as for birds undergoing the second prebasic molt or SPB. For both codes, we discuss their applicability using examples based on actual banding data. Our proposed codes will improve the utility of the WRP system by better refining age brackets and by expanding its applicability to a diverse array of taxa.