Many large birds do not have enough time to replace all their primaries and secondaries during a single prebasic molt—the annual molt, which often takes place in late summer or fall in the northern hemisphere. The resultant, incomplete replacement patterns among these tracts can be used to age these birds, in some cases up to and beyond their fourth or fifth annual plumage cycles. While there has been increasing focus on “reading” replacement patterns among primaries to age birds, patterns among secondaries have often been regarded as “random” or “too complex” to be useful. (A quick reminder: The primaries are the powerful outer flight feathers of the wing; the secondaries are the inner flight feathers of the wing. Together, the primaries and the secondaries are known as the remiges.)
In this note, I encourage greater awareness of the value of the secondaries in aging large birds. For a case study, I reconsider the age of one of the albatrosses in a recent article in Birding (Flood 2015). But before we get to that, let’s consider the order, or “sequence,” in which birds molt their secondaries.