Daily vocal exercise is necessary for peak performance singing in a songbird

Abstract

Vocal signals, including human speech and birdsong, are produced by complicated, precisely coordinated body movements, whose execution is fitness-determining in resource competition and mate choice. While the acquisition and maintenance of motor skills generally requires practice to develop and maintain both motor circuitry and muscle performance, it is unknown whether vocal muscles, like limb muscles, exhibit exercise-induced plasticity. Here, we show that juvenile and adult zebra finches (Taeniopygia castanotis) require daily vocal exercise to first gain and subsequently maintain peak vocal muscle performance. Experimentally preventing male birds from singing alters both vocal muscle physiology and vocal performance within days. Furthermore, we find females prefer song of vocally exercised males in choice experiments. Vocal output thus contains information on recent exercise status, and acts as an honest indicator of past exercise investment in songbirds, and possibly in all vocalising vertebrates.

Daily singing of adult songbirds functions to maintain song performance independently of auditory feedback and age

“…Our results indicating that the long-term SS induces substantial changes in adult song structure and amplitude are largely consistent with the findings of a recent study by Adam et al 19 . Although they employed a different SS method, both our results and theirs lead to virtually the same conclusion.…”

“…Although they employed a different SS method, both our results and theirs lead to virtually the same conclusion. However, our study includes the following new findings that were not reported in Adam et al 19 : SS-induced song changes are mostly recovered within a short period of free singing, providing more direct evidence for the function of undirected singing in maintaining adult song performance; the recovery of song performance following the SS period does not necessarily require AF, revealing novel, AF-independent mechanisms for the maintenance of song performance; SS-induced song changes do not strongly depend on age, highly contrasting with AF-dependent song plasticity that has previously reported 16 , 17 . Because Adam et al 19 also reported the experimental findings that are not included in our current study, these two studies complement each other to significantly advance our understanding of the mechanisms by which adult birds maintain song performance through daily undirected singing.…”

“…Taken together, our findings provide evidence suggesting that zebra finches maintain their song performance by preventing age-independent song changes through the physical act of daily singing throughout life. Because male zebra finches produce courtship songs with a motif structure very similar to that of undirected song 10 (although variability and speed are slightly different), it is likely that they maintain the song production system in an optimal condition through undirected singing to prepare for the best song performance in reproductive contexts 19 .…”

“…Adam et al 19 examined the physiological mechanisms underlying SS-induced changes in song performance. They reported evidence that SS-induced song changes are caused, at least in part, by physiological and anatomical changes in the syringeal muscles responsible for song production 19 , similar to the atrophy of skeletal muscles that is generally known to be caused by a lack of physical activity. It is also possible, however, that SS-induced song changes are attributable to changes in the neural circuits that generate song structure.…”

“…This AF-dependent function of undirected singing, however, appears to be limited to young adult birds, as the removal of AF causes substantial changes in song structure in relatively young birds but not in old birds 16 , 17 . Nevertheless, old birds still sing many renditions of undirected songs every day 12 , 18 , raising the possibility that undirected singing serves another function in addition to the AF-dependent maintenance of song structure 19 . To explore novel functions of daily undirected singing, we suppressed undirected singing in adult zebra finches for two weeks (Fig.…”