The moult of the Fan-tailed Warbler

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Abstract
Fan-tailed warblers, both adults and juveniles, have a complete molt in autumn, mainly between June and October. Adult males molt in about 92 days while adult females average 67 days. First-year birds molt in 75 days (females) and 81 days (males). From spring to early autumn, birds can be aged according to abrasion of wing and tail feathers. Adults, well as some juveniles, can also be sexed. Primaries molt in the normal way, i.e., descendantly, but molt of the secondaries proceeds in both directions and finishes on the 4th. Many birds molt the tertiaries and some of the greater coverts twice, at the beginning and at the end of molt. This phenomenon apparently has not been encountered previously in other Palearctic passerines studied. Exceptionally, some primaries and secondaries also may be molted twice. Head feathers take longest to molt. Adult males start molting about 2 wk before females. Many juveniles, especially males, suspend molt and show breeding behavior. When molt is resumed the renewed feathers are molted once again. First-year females from early broods develop brood patches. Young hatched in the latter part of the season start to molt at an earlier age than those fledging from early broods.