Organismal Behavior

How seemingly stereotyped song changes in a daily fashion

The ability to learn and perform complex motor skills has been shown across species to depend on time of day. One such complex motor skill that has been shown to oscillate daily is song produced by songbirds. The study of song is particularly useful for understanding mechanisms driving the learning of vocalizations and the cellular and morphological changes that accompany changes in song production rate and quality. In one such songbird, Gambel’s white-crowned sparrow (Zonotrichia leucophrys gambelii), the production of song and the underlying neural circuit that controls this song changes dramatically between breeding and nonbreeding seasons. We sought to determine whether song also changed on a finer time scale – that is daily. Thus, to understand the daily temporal dynamics of song production in white-crowned sparrows, we analyzed song production rate, spectral features, and stereotypy of more than 1500 songs produced over the course of two consecutive days by sparrows maintained in breeding conditions. We identified daily patterns in song rate, frequency, entropy, power, and energy of breeding song within both individual birds and pooled bird data. The demonstration of daily oscillations in song rate and spectral features of white-crowned sparrows supports both anecdotal descriptions of ‘the morning chorus’ and growing evidence on the modulation of the song control circuit by the internal circadian clock. Having shown daily changes in song production in white-crowned sparrows, we can now begin to study the relationship between song production, cellular changes like neuronal birth and death that occur within the song circuit, and the endogenous circadian clock.