Light affects parental provisioning behaviour in a cavity-nesting Passerine

Nocturnal bird species possess special adaptations to maximise visual efficiency under low light levels. However, some typically diurnal species also experience low-light environments. For example, cavity-nesting Passerines raise broods in dark cavities and search for food in light-abundant surroundings. It is not clear whether they possess special adaptations for low light vision or breed in cavities at the expense of impaired parental care. In this study, we tested whether light conditions affect the provisioning efficiency of great tits. We experimentally tested how the level of natural and artificially increased illumination inside nest boxes affects parental feeding duration, frequency and timing. We monitored 15-hours of provisioning activity of great tit parents when nestlings were day 7 post hatch. We used traditional “dark” nest boxes and “bright” nest boxes with increased illumination obtained by using semi-transparent plastic windows. The duration of single feedings were, on ...