Molts and Plumages of Ducks (Anatinae): An Evaluation of Pyle (2005)

Abstract

Ducks are unusual because males of most Holarctic species acquire brightly-pigmented breeding plumages in autumn and winter and not spring as with most other birds. Based on an evaluation of molt phenology of ducks under the system of molt terminology invented by Humphrey and Parkes (1959), Pyle (2005) concluded that, for most North American duck species, the molt that produces bright plumages is basic in nature, the molt that typically produces a short-lived, dull “eclipse” plumage in spring or summer is alternate in nature, and the annual wing molt that largely occurs between these two molts is part of the subsequent recharacterized prebasic molt. For various reasons, it appears more likely that the timing of conventional prealternate molts in most Holarctic duck species has accelerated forward over time to autumn and winter in response to selection for early courtship and pairing, with resulting changes in the duration of alternate and basic plumages. These reasons include acceleration in the timing of the prealternate molt in sea ducks after they reach the age of first breeding. An accelerated timing of prealternate molts can explain why certain ducks exhibit an ephemeral, limited first prebasic molt, which appears to be a lost molt and not a virtually nonexistent, unique preformative molt as maintained by Pyle (2005). The accelerated timing hypothesis also can explain why the extent of prealternate molts may have become more complete and the extent of prebasic molts may have become less complete in certain ducks. The accelerated timing hypothesis appears more parsimonious from an evolutionary perspective than the system of Pyle (2005), and does not require the categorical rejection of plumage color and pattern in molt homology analyses, as advocated by Pyle (2005).