Do birds in flight respond to (ultra)violet lighting?

Abstract

Background: Concerns for bird collisions with wind turbines affect the deployment of onshore and offshore windpower plants. To avoid delays in consenting processes and to streamline the construction and operation phase, functional mitigation measures are required which efficiently reduces bird mortality. Vision is the primary sensory system in birds, which for a number of species also includes the ultraviolet spectrum. Many bird species that are known to collide with offshore wind turbines are sensitive in the violet or ultraviolet spectrum. For species that are mainly active at lower ambient light levels, lighting may deter birds from the lit area. Utilizing (ultra)violet lights may in addition not disturb humans. However, we do not know whether UV-sensitive birds in flight actually respond behaviourally to UV lights. Methods:We therefore tested the efficacy of two types of lights within the violet (400 nm) and ultraviolet (365 nm) spectrum to deter birds from the lit area. These lights were placed vertically and monitored continuously between dusk and dawn using an avian radar system. Results:Relative to control nights, bird flight activity (abundance) was 27% lower when the ultraviolet light was on. Violet light resulted in a 12% decrease in overall abundance, and in addition, a vertical displacement was seen, increasing the average flight altitude by 7 m. Although temporal changes occurred, this effect persisted over the season below 40 m above sea level. Conclusions:Although the results from this pilot study are promising, we argue there still is a long way to go before a potentially functional design to mitigate collisions that has proven to be effective in situ may be in place.

Paint it black: Efficacy of increased wind turbine rotor blade visibility to reduce avian fatalities

“…Bostrom et al., 2016). Although ultraviolet paint (or other coloring) or lighting has also been proposed, these have so far shown limited efficacy (Hodos, 2003; May, Åström, Hamre, & Dahl, 2017; Young, Erickson, Strickland, Good, & Sernka, 2003). In addition, not all species are sensitive within the ultraviolet spectrum (Lind, Mitkus, Olsson, & Kelber, 2014).…”

Assessing bird avoidance of high-contrast lights using a choice test approach: implications for reducing human-induced avian mortality

“…This is particularly interesting because previous studies have suggested the use of these lights to reduce bird collisions. For instance, ultraviolet lights have been recommended to minimize collisions with wind turbines ( May et al, 2017 ); green lights, with offshore platforms ( Poot et al, 2008 ); and white lights, with communication towers ( Gehring, Kerlinger & Manville, 2009 ). However, all these studies were observational in nature (i.e., recording wild bird behavior/mortality around objects with different types of lighting) and did not control for many of the factors that could lead to misleading results (i.e., variations in individual identity, hunger levels across individuals, flying heights across trials, etc.…”

“…If lighting is employed as a means of minimizing bird collisions with human-made structures and vehicles through enhanced detection and avoidance, we must understand how the visual conspicuousness of lights affects choice behavior. This is important because of the variation in the type and degree of behavioral responses of birds to different wavelengths of light ( Gehring, Kerlinger & Manville, 2009 ; De Jong et al, 2015 ; May et al, 2017 ; Hunt, McClure & Allison, 2015 ). Our two-tiered methodological approach provides one way of tackling this complex problem, as behavioral responses to different suprathreshold visual signals can be highly variable.…”

Mitigating biodiversity impacts associated with solar and wind energy development: guidelines for project developers

“…These Guidelines follow CSBI's definition of mitigation hierarchy. To note, there are alternative approaches to implementing the mitigation hierarchy to achieve the same result, such as that detailed in May (2017), which advocates a five-step approach tied to the decision gates for wind farm development: 1) avoid when planning, 2) minimise while designing, 3) reduce at construction, 4) compensate during operation, and 5) restore as part of decommissioning. avoid, minimise, restore and offset.…”