THE IMPACT OF THE LIGHTS OUT TEXAS ADVISORY CAMPAIGN ON NIGHT SKY BRIGHTNESS AND BIRD COLLISION FATALITIES

Abstract

Light pollution caused by artificial light at night (ALAN) is accelerating across the globe. ALAN interferes with biological processes such as nocturnal bird migration in several ways including mortality through bird window collisions. Some cities have started light reduction advisory campaigns during migration seasons to combat the adverse effects of ALAN on birds, but there has yet to be quantification of sky brightness reduction during these advisories. For chapter 1, I measured night sky brightness (NSB) in metro Dallas and Houston, Texas using Sky Quality Meters (SQMs) on 12 Lights Out, Texas advisory participant building rooftops to document the efficacy of the program. Though I found these cities are brightly lit compared to their rural counterparts, I did not find significant difference in light pollution reduction during the advisory. In chapter 2, I address if changes in regional night sky brightness impact the number of nightly fatalities documented. I present generalized linear mixed models assessing nightly nocturnal fatalities in the cities of Dallas and Houston during the 2022-2023 Lights Out, Texas monitoring season as compared to regional migration traffic rate and local atmospheric conditions including weather, lunar, and night sky brightness (NSB). Migration traffic rate has the strongest positive relationship with bird window fatalities across cities and seasons. Occasionally, weather variables that are conducive to bird migration in the spring and fall were also positively related to fatalities. Moon illumination percent was also consistently negatively associated with bird fatalities across cities and seasons. While these mechanisms are unclear, I hypothesize a more complex relationship between natural light, artificial light, and glass is at play. While NSB was not a significant variable in the models, the Lights Out, Texas campaign retains potential for effectiveness at the window scale. More research is needed on scales and complex interactions at which these variables influence bird mortality.