FEATURED PHOTO: DELAYED PREFORMATIVE MOLT IN THE BARN SWALLOW

Abstract

The Barn Swallow (Hirundo rustica) is among those passerines whose molt follows the “complex basic strategy” (Howell et al. 2003). This means that adults have only a single (prebasic) molt each plumage cycle, whereas first-year birds have an additional preformative molt (traditionally termed the first prebasic molt) in their first plumage cycle, bridging the period between juvenile plumage and entry into the adult cycle. In most passerines the preformative molt is partial, but in swallows it is complete, or nearly so. That is, the young birds replace all of their feathers with a plumage essentially identical to that of the adult, and this plumage is worn through their first breeding season. In North American Barn Swallows (H. r. erythrogaster) both the definitive prebasic and preformative molts take place primarily on the winter grounds, the former between August and February, the latter between October and April (Pyle 1997). Thus the latest first-cycle birds should complete growth of their outer primaries in April.