A field survey to investigate why nightjars frequent roads at night

Abstract

Nightjars throughout the Afrotropical Region regularly frequent roads at night and during the twilight of dusk and dawn. Most species exhibit this behaviour and numerous individuals are killed by road traffic. Many theories have been advanced to explain the presence of nightjars on roads at night, but very little fieldwork has been carried out to test them. For a period of a year we carried out a weekly survey of nightjars on a selected road network near Harare in Zimbabwe. All nightjar encounters were documented in relation to variations in road surface, road width, adjacent habitat, arc of sky visible and other variables, such as the time of night, moon phase and weather conditions. None of these factors provided a complete explanation for the presence of nightjars on the roads surveyed. Neither were any of the nightjars seen dust bathing, taking grit or picking up insects from the road. Many were seen actively hunting flying insects, especially at dusk, and palpation of the stomachs of those caught confirmed that they had fed well during the evening hours. They were clearly using the road as an observation platform for hunting during the first few hours after sunset and then as a convenient place for resting and digesting. A nightjar sitting on an open road is certainly in a good position to see flying insects silhouetted against the twilight sky.