Life course analysis of birdsong reveals maturation and senescence of repeatable characteristics

Signalers may benefit in some contexts from advertising their ages, for example in courting potential mates. Receivers in turn may benefit from assessing a signaler's age, even in cases where their doing so is against the signaler's interests. Cues to age contained in signals thus may have important fitness consequences. In birds, males of many species have been shown to display delayed maturation of their songs, resulting in older males singing songs that are higher in quality in one or more characteristics. Conversely, it seems possible that songs might eventually deteriorate with age as an aspect behavioral senescence. Studies of birdsong long enough to test both possibilities are quite uncommon, with nearly all studies of age-dependent changes in birdsong spanning 3 or fewer years of males’ lives. Here we present the longest longitudinal analysis of male birdsong to date, in which we analyze songs recorded over up to 11 years of the lives of captive male swamp sparrows. We find that...