Short-term exposure to artificial light at night has little effect on parental provisioning or nestling growth in a breeding aerial insectivore ( Tachycineta bicolor )

Abstract

Increased urbanization has altered nightscapes on a global level, with artificial light at night (ALAN) often extending well beyond localized urban centers. In breeding birds, previous studies have shown that ALAN can disrupt circadian rhythms with subsequent impact on the timing of various physiological and behavioral processes. Although biparental care in birds often involves coordinated efforts, to date, relatively few studies have examined effects of ALAN on males and females simultaneously, especially in the case where coordination may be affected by one individual’s experience of an environmental stressor. We experimentally installed LED lights in Tachycineta bicolor (Tree Swallow) nest boxes to simulate low-intensity ALAN levels found near cities. Swallows exhibit biparental care, yet only the female spends extensive time in the nest box. We monitored adult daytime nest visitation rate and nocturnal body temperature throughout the nestling stage of the development. Females maintained similar body temperatures throughout the night, regardless of whether they were exposed to ALAN or not. Males and females from ALAN treatments maintained similar nest visitation rates and activity offsets to individuals from control nests, with males initiating activity slightly later than females. Nestlings reared under ALAN reached a similar day 12 body mass and fledged at a similar rate as controls. Overall, this work suggests that the effects of short-term, low-intensity (1.8 lux) ALAN may not affect parental investment in species that coordinate care.