Night-time nestling provisioning in urban peregrine falcons

Most bird species are diurnal, with visually guided foraging, and it is natural to assume that highly visual predators which intercept moving targets, such as the peregrine falcon Falco peregrinus, will be particularly constrained in their foraging activity by light levels. However, there are anecdotal reports of nocturnal foraging by raptors, notably when there are high levels of artificial light at night (‘ALAN’). We focus on the nocturnal feeding behaviour of breeding urban-dwelling peregrine falcons by using our database of webcam-monitored feeding events from across 30 urban nest locations in the UK. Out of 66 nesting attempts observed between 2019 and 2023, in 28 (42%), we observed peregrine falcons feeding their nestlings at least once during the strict night period (between the end and subsequent start of civil twilight). Supporting the view that night feeding is facilitated by light levels, there was an interaction between lunar illumination and ALAN: nocturnal feeding events were more common between the first and third quarter of the moon in locations where the night sky had more artificial light. This study provides valuable insights into the nocturnal foraging and breeding behaviour of a typically diurnal predator in urban locations.