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Bennett, V. J., & Hale, A. M. (2014). Red aviation lights on wind turbines do not increase bat-turbine collisions. Animal Conservation, 17(4), 354–358.
Abstract: Many hypotheses have been proposed to explain why batâwind 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 batâwind 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.
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Buchanan, B. W. (1993). Effects of enhanced lighting on the behaviour of nocturnal frogs. Animal Behaviour, 45(5), 893–899.
Abstract: Biologists studying anuran amphibians usually assume that artificial, visible light does not affect the behaviour of nocturnal frogs. This assumption was tested in a laboratory experiment. The foraging behaviour of grey treefrogs, Hyla chrysoscelis, was compared under four lighting conditions: ambient light (equivalent to bright moonlight, 0·003 lx), red-filtered light (4·1 lx), low-intensity 'white' light (3·8 lx), and high-intensity 'white' light (12·0 lx). The treatments were chosen to correspond to standard methods of field observation of frog behaviour. The foraging behaviour of frogs in the four treatments was observed using infra-red light that was invisible to the frogs. The ability of the frogs to detect, and subsequently consume prey was significantly reduced under all of the enhanced light treatments relative to the ambient light treatment. Thus, the use of artificial light, within the visible spectrum of the frogs' eyes, can influence the outcome of nocturnal behavioural observations. These results lead to the recommendation that anuran biologists use infra-red or light amplification devices when changes in frogs' visual capabilities may influence the conclusions drawn from a study.
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Clewley, G. D., Plummer, K. E., Robinson, R. A., Simm, C. H., & Toms, M. P. (2015). The effect of artificial lighting on the arrival time of birds using garden feeding stations in winter: A missed opportunity? Urban Ecosystems, 19(2), 535â546.
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.
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Dwyer, R. G., Bearhop, S., Campbell, H. A., & Bryant, D. M. (2013). Shedding light on light: benefits of anthropogenic illumination to a nocturnally foraging shorebird. J Anim Ecol, 82(2), 478–485.
Abstract: Intertidal habitats provide important feeding areas for migratory shorebirds. Anthropogenic developments along coasts can increase ambient light levels at night across adjacent inter-tidal zones. Here, we report the effects of elevated nocturnal light levels upon the foraging strategy of a migratory shorebird (common redshank Tringa totanus) overwintering on an industrialised estuary in Northern Europe. To monitor behaviour across the full intertidal area, individuals were located by day and night using VHF transmitters, and foraging behaviour was inferred from inbuilt posture sensors. Natural light was scored using moon-phase and cloud cover information and nocturnal artificial light levels were obtained using geo-referenced DMSP/OLS night-time satellite imagery at a 1-km resolution. Under high illumination levels, the commonest and apparently preferred foraging behaviour was sight-based. Conversely, birds feeding in areas with low levels of artificial light had an elevated foraging time and fed by touch, but switched to visual rather than tactile foraging behaviour on bright moonlit nights in the absence of cloud cover. Individuals occupying areas which were illuminated continuously by lighting from a large petrochemical complex invariably exhibited a visually based foraging behaviour independently of lunar phase and cloud cover. We show that ambient light levels affect the timing and distribution of foraging opportunities for redshank. We argue that light emitted from an industrial complex improved nocturnal visibility. This allowed sight-based foraging in place of tactile foraging, implying both a preference for sight-feeding and enhanced night-time foraging opportunities under these conditions. The study highlights the value of integrating remotely sensed data and telemetry techniques to assess the effect of anthropogenic change upon nocturnal behaviour and habitat use.
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Jetz, W., Steffen, J., & Linsenmair, K. E. (2003). Effects of light and prey availability on nocturnal, lunar and seasonal activity of tropical nightjars. Oikos, 103(3), 627–639.
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.
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