Developmental effects of daily food availability times on song behaviour and neuronal plasticity of song-control system in male zebra finches.

Food availability is a major ecological factor and affects body condition and sexual traits. Here, we investigated whether males' song behaviour, a trait for female mate choice, was sensitive to the food availability period and its timing in songbirds. We manipulated daily food availability to 4 h in the morning or evening, with controls on food ad libitum, and assessed its effects on song behaviour and forebrain song control system in male zebra finches that were held as adult (parent) or offspring (since birth) at 24 ± 2 °C under 12 h daily photoperiod. Food restriction significantly affected both temporal and spectral features of daily song in offspring, not the parent. In offspring, we found reduced mesor (mean 24-h levels), attenuated amplitude (daily maxima relative to mesor) and altered acrophase (estimated time of daily maxima) of 24-h rhythm, and reduced motif length (in morning-fed), per motif unique syllables and an enhanced song pitch (in evening-fed). There was also a positive correlation of motif length with cheek patch and plasma testosterone levels, and of per motif syllables with cheek patch and daily activity levels in offspring. Among main song controlling forebrain nuclei, LMAN and HVC were reduced in size, and Area X and HVC showed decreased neuronal recruitment in offspring on food restrictions. These results demonstrate the importance of daily food availability and its timing in determining males' sexual signals, and support growing evidence that among vertebrates well-fed males contain reproductive traits that females use for its mate choice.