We discovered and monitored a nest of the Rusty-winged Barbtail (Premnornis guttuligera) on the eastern slope of the Andes in Napo Province, Ecuador. The nest, in a hollow Cyathea tree-fern snag, was a deep cup composed entirely of Cyathea tree-fern petiole scales (ramenta). A single nestling fledged successfully on 13 March 2002. During the latter half of the nestling period, adults visited the nest with food a mean of 4.7 ± 1.9 (SD) times/h and removed fecal sacs 2.2 ± 1.1 times/h. Nest visitation rates generally decreased throughout the day. Adult Rusty-winged Barbtails foraged by gleaning from or probing into suspended dead leaves or moss, often while hanging onto the substrate, and did not hitch up trunks or creep along branches. Nest structure, composition, and location, and foraging behavior all raise doubts about the taxonomic placement of Premnornis in the Margarornis treerunner-barbtail assemblage.