Abstract: Many hypotheses have been proposed to explain why bat–wind turbine collisions occur; however, most of these hypotheses have yet to be tested and with high numbers of bat fatalities reported annually at wind resource facilities globally, there is a real need to understand this phenomenon. In this study, we tested whether aviation lighting influenced the number of bat fatalities at wind turbines. Thus, at a utility-scale wind facility in north-central Texas, we explored whether bat fatalities were higher at wind turbines with red flashing aviation lighting compared with turbines without such lighting. Over a 5-year period, we recorded fatalities at wind turbines as part of a long-term fatality monitoring programme. During standardized searches, we collected 916 bat carcasses representing all six species known to be present at the site. We found that bat fatalities were higher at wind turbines without aviation lighting compared with those with; a pattern that was driven by one species, Lasiurus borealis, and there was no significant difference between fatalities at wind turbines with or without aviation lighting for any other species. Our study demonstrates that wind turbines should continue to be fitted with synchronized, flashing red aviation lights, as this form of lighting does not appear to be one of the potential causes of bat fatalities at wind resource facilities. We therefore support further research that explores possible alternative causes of bat–wind turbine interactions. More specifically, we reiterate that there is still a pressing need to determine the aspects of bat ecology that result in individuals coming into contact with wind turbines.

Abstract: The proliferation of artificial lighting at night is one of the key anthropogenic changes associated with urbanised areas as well as some non-urban areas. Disruption to natural light/dark regimes can have considerable effects on the timing of different behaviours of birds, particularly during the breeding season. However, the effect of artificial lights on the timing of behaviours during winter has received relatively little attention, despite the fact that time partitioning of foraging can have implications for avian winter survival. In this study, we assess at a landscape scale during winter, whether birds arrive at feeding stations earlier in areas with increased levels of artificial lighting using data from a citizen science project. Arrival times of the ten most commonly recorded species were associated with a combination of the density of artificial lights, temperature, rainfall and urban land cover. We found no evidence that birds advance the onset of foraging in gardens with more artificial lights nearby; contrary to our prediction, birds generally arrived later into these areas. This is possibly a response to differences in food availability or predation risk in areas with more artificial lights. We conclude that artificial light at night may not be as important for driving the timing of foraging behaviour in winter as previously thought, but it remains to be seen whether this represents a missed opportunity to extend the foraging period or an adaptive response.

Abstract: Nightjars and their allies represent the only major group of visually hunting aerial insectivores with a crepuscular and/or nocturnal lifestyle. Our purpose was to examine how both light regime and prey abundance in the tropics, where periods of twilight are extremely short, but nightjar diversity is high, affect activity across different temporal scales. We studied two nightjar species in West African bush savannah, standard-winged nightjars Macrodipteryx longipennis Shaw and long-tailed nightjars Caprimulgus climacurus Vieillot. We measured biomass of potential prey available using a vehicle mounted trap and found that it was highest at dusk and significantly lower at dawn and during the night. Based on direct observations, both nightjars exhibit the most intense foraging behaviour at dusk, less intense foraging at dawn and least at night, as predicted by both prey abundance and conditions for visual prey detection. Nocturnal foraging was positively correlated with lunar light levels and ceased below about 0.03 mW m−2. Over the course of a lunar cycle, nocturnal light availability varied markedly, while prey abundance remained constant at dusk and at night was slightly higher at full moon. Both species increased twilight foraging activity during new moon periods, compensating for the shorter nocturnal foraging window at that time. Seasonally, the pattern of nocturnal light availability was similar throughout the year, while prey availability peaked shortly after onset of the wet season and then slowly decreased over the following four months. The courtship and breeding phenology of both species was timed to coincide with the peak in aerial insect abundance, suggesting that prey availability rather than direct abiotic factors act as constraints, at least at the seasonal level. Our findings illustrate the peculiar constraints on visually orienting aerial nocturnal insectivores in general and tropical nightjars in particular and highlight the resulting nocturnal, lunar and seasonal allocation of activities.