Effects of Artificial Light at Night on Avian Provisioning, Corticosterone, and Reproductive Success

Abstract

Artificial light at night (hereafter ‘ALAN’) affects 88% of the land area in Europe and almost half of the land area in the US, with even rural areas exposed to lights from agricultural and industrial buildings. To date, there have been few studies that assess the impacts of ALAN on both wildlife behavior and physiology. However, ALAN may alter energy expenditure and/or stress physiology during the breeding period, potentially reducing reproductive success and resulting in conservation implications. Here, we experimentally exposed adult female and nestling tree swallows (Tachycineta bicolor) to ALAN. We then measured the effects of ALAN compared to control conditions on parental behavior (provisioning rate), nestling physiology (corticosterone levels), and reproductive success (likelihood of all eggs hatching and all nestlings fledging per nest). Our results showed that ALAN-exposed females provisioned their nestlings at lower rates than control females. Although relatively weak, our results also suggested that ALAN-exposed nestlings had reduced baseline and increased stress-induced corticosterone compared to control nestlings. ALAN-exposed nestlings also showed greater negative feedback of circulating corticosterone. We found no support for our prediction that ALAN would reduce nestling body condition. Finally, we found some support for a negative effect of ALAN on the likelihood that all eggs hatched in a given nest, but not the likelihood that all nestlings fledged. Therefore, while it is possible that the behavioral and physiological changes found here result in long-term consequences, our results also suggest that direct ALAN exposure alone may not have substantially large or negative effects on tree swallows. Exposure regimes for free-living birds, such as exposure to a combination of anthropogenic disturbances (i.e. ALAN and noise pollution) or direct and indirect effects of ALAN (i.e. effects on physiology due to direct light exposure and alterations in food availability), may produce different results than those found here.

Phenotypic signatures of urbanization? Resident, but not migratory, songbird eye size varies with urban‐associated light pollution levels

“…In line with findings on the Carolina Wren, cardinal eye size was best explained by light pollution and brightness (difference of 0.07 AIC c between the models; Table S6), both of which were ranked >2 AICc above the null model. We also While recent research has documented behavioral responses of birds to anthropogenic sources of light pollution (e.g., Dominoni et al, 2013;Injaian et al, 2021), our findings provide some of the first evidence that birds may respond to anthropogenic alterations of their sensory environments through changes in eye morphology. Consistent with our predictions, residential birds (i.e., Northern Cardinals and Carolina Wrens) inhabiting core areas had smaller eyes than their edge counterparts.…”

Within-individual consistency and between-individual variation in the shapes of eggs laid by tree swallows (Tachycineta bicolor)

“…For this study, we visited each nest during the first week of incubation and photographed eggs to measure size and shape (example photographs in Figure 1). During the years of study, many nests at these sites were included in a variety of experiments focused on manipulating environmental stressors (e.g., Injaian et al, 2021; Taff et al, 2021). However, all of these experimental manipulations began during mid-incubation, after eggs had been laid and pictures had been taken.…”

Lights, Noise, Nesting? Effects of Human Disturbances on Reproduction in Cavity-Nesting Songbirds

“…Human activities often result in additional forms of disturbance, including sensory pollutants such as ambient noise and artificial light at night (ALAN; Swaddle et al 2015). Sensory pollutants are known to affect a variety of species including bats, moths, hermit crabs, and whales (Dominoni et al 2020b, Halfwerk and Slabbekoorn 2015, Swaddle et al 2015, but the impacts these pollutants have on birds are currently some of the most commonly explored relationships within the field (Dominoni et al 2020b;Halfwerk et al 2011;Injaian et al 2018Injaian et al , 2021.…”

“…Noise pollution can negatively influence parental behavior, parent–nestling feeding interactions and communication, nestling body size, post-fledging survival, and general reproductive success in Tree Swallows (Dale et al 2021, Injaian et al 2018). ALAN also seems to negatively impact their reproductive success in some cases (Injaian et al 2021). However, ALAN has been found to extend parental foraging time at dawn and dusk into the so-called night-light niche for some avian species, allowing for more nestling feeds per day (Dominoni et al 2020a, Titulaer et al 2012, Wang et al 2021).…”