Ontogenetic exposure to light influences seabird vulnerability to light pollution

Abstract

Light pollution critically affects fledglings of burrow-nesting seabirds, leading to massive mortality events. A successful management of this pollutant depends upon a comprehensive understanding of the factors influencing visual sensitivity and corresponding behaviours towards light. Factors shaping the development of the visual system could account for variation in seabirds’ vulnerability to light pollution. We investigated how Cory's shearwater chicks respond to selected contrasting artificial light stimuli. Chicks were subjected to blue and red light treatments, and repeatedly tested throughout the nestling period. We analysed behavioural responses (number, timing, and orientation of reactions) to determine how age, exposure to experimental light stimuli, and spectra influenced the onset of visually guided behaviours, thus inferring drivers of vulnerability to light pollution. Repetitive exposure to light significantly increased the number of reactions, and chicks predominantly displayed light avoidance behaviour. We did not find differences in the number of reactions, timing and orientation between blue and red light treatments. The responses did not differ across different age groups. These results provide empirical evidence for the contribution of the light available in the rearing environment to seabird visual development. They support the hypothesis that differential exposure to light during the growth period influences responses to artificial light, and that the state of visual development at fledging could be a main driver of the age bias observed during seabird fallout events. It is thus important to evaluate lighting schemes at both urban and natural areas, and the yet unknown consequences already affecting the populations.

Do seabirds dream of artificial lights? Understanding light preferences of Procellariiformes

“…However, age-specific differences in the frequency and time taken to make a choice were identified. Indeed, former studies showed that Cory’s shearwater chicks displayed a preference for dark environments when exposed to artificial light at a closer range (Atchoi et al ., 2023), and adults of the closely related species, such as Manx and Yelkouan shearwaters, avoided their colony when it was sporadically exposed to artificial light (Syposz et al ., 2021; Austad et al ., 2023). Both age groups displayed stronger avoidance of shorter wavelength artificial lights.…”

“…Disorientation could be a result of artificial light interfering with the bird’s visual system. Studies have described an underdeveloped and untrained visual system in growing Procellariiformes chicks: older Leach’s-storm petrel chicks Hydrobates leucorhous reacted more times to light stimuli than younger ones, i.e., underdeveloped (Mitkus, Nevitt and Kelber, 2018), and growing Cory’s shearwater chicks reacted more to light stimuli the more they had been previously exposed to light, i.e., trained (Atchoi et al ., 2023). In the current study, fledglings were slower to react than adults in general (Figure 3), suggesting that the light-induced effect is stronger for the younger birds.…”

“…The red and blue LED light systems used in this study were the same as in Atchoi et al, 2023. Briefly, the spectral sensitivities were modelled based on visual parameters of the wedge-tailed shearwater Ardenna pacifica , the most closely related species to Cory’s shearwater for which such data exist.…”

“…These illuminances correspond to light levels at civil twilight (Cronin T. W., 2014) and are comparable to what a chick would be exposed to outside its burrow after sunset. Further details on the red and blue light system, including dimensions, measurements, and sensitivity modelling, can be found in Atchoi et al, 2023, and in the supplemental material (Figure S2).…”

Moonlight diminishes seabird attraction to artificial light

“…So, moonlight during these nights might be enough to provide the needed visual stimuli to develop their visual systems. In this sense, a higher exposure to artificial light during ontogeny has led to a higher response to light stimuli in experimental shearwater chicks (Atchoi et al, 2023). Clearly, further studies are needed to explain how moonlight affects the light attraction of seabirds.…”