A comparative study of post‐juvenile moult in four species ofSylviawarbler

This paper contains the commencement, sequence, extent and duration of moult, and body weights during moult in first‐year Sylvia warblers. Lesser Whitethroats, Whitethroats and Blackcaps moulted the five feather areas in the same sequence but Garden Warblers differed in the sequence of wing‐covert moult. Extent of moult was similar, except for wing‐coverts, which differed both within and between species with Lesser Whitethroats moulting the most feathers and Garden Warblers the least. Variations in duration of moult were also present with Garden Warblers the first to start and finish moult and Blackcaps the last. Mean body weights (in all species) followed similar patterns with higher mean weights when in mid‐moult suggesting that energy demands were highest when the greatest number of feathers were growing. Body weights for birds in fresh plumage are discussed speculatively.