Fig. 3

Variation in hourly song output of male Savannah Sparrows with respect to breeding stage (pre-pairing, fertile, incubation, hatchling, and fledgling). Before pairing, male singing activity peaked in the morning (i.e. a dawn chorus) and was nearly absent at dusk. During the fertile stage, after pairing, male singing activity was low until the end of the day (i.e. a dusk chorus). Whiskers show standard error round the mean value for each hour, per individual, for n = 34 males