Factors related to bird collisions with buildings along the coast of Lake Erie.
Leandro Marcos Lessin, MS
Advisor: Stephen N. Matthews
In North America, the replacement of greenspaces with human-made structures causes hundreds of millions, if not billions, of avian fatalities every year. Through the continuous increase in urbanization, threats to avian wildlife are exacerbated by a multitude of related factors such as habitat loss, fragmentation, and pollution. Bird collisions with buildings are an integral component of these threats because they directly cause avian mortality, and they are expected to increase as human populations continue to grow in urban areas. Bird collisions with buildings represent the largest source of collision mortalities, ahead of collisions with windmills, power lines, and vehicles. Cities serve as physical impediments for numerous bird species, as many urbanized landscapes are located along migratory routes. Birds play an important role in the proper functioning of ecosystems, and they also play an important role within human societies. Therefore, it is important to explore determinants of bird collisions with buildings to identify effective mitigation strategies that aim to counter the rapid decline of bird populations.
Previous studies have identified that numerous factors correlate with bird collisions with buildings. These factors include species’ life-history traits, artificial lighting at night, building characteristics, and atmospheric conditions. There are likely a multitude of other factors influencing bird collisions with buildings at any point in time, and this further increases the complexities behind collision dynamics. I evaluated previously identified factors related to bird collisions with buildings to test their influence on bird collisions in Cleveland, Cuyahoga County, Ohio, during fall of 2017. I identified that life-history strategies related to migration distance and foraging height, along with family groupings, differentiated collision frequencies. For example, long-distance migrant and warbler (Family Parulidae) species were overrepresented in their collision frequencies when compared to their local relative abundances. Next, I explored patterns of collision over time and found a complex interaction of variables related to bird collisions with buildings. Variables included in the final model included atmospheric pressure, peak wind speeds, temperature, relative abundance, date, and flying altitude. I also found that time lags were important when exploring determinants of collision. For example, atmospheric conditions (i.e., peak wind speeds) one day before collision events were critical in capturing changing weather conditions over time. This study also found an important multiplicative interaction between Julian date and maximum dry bulb temperature when predicting collision numbers, and this highlights the need to include complex variable interactions when modeling and predicting collision risk. Every year, there are large numbers of bird collisions with buildings, so when exploring and creating efficient mitigation efforts, it is crucial to consider changing atmospheric conditions and avian movement patterns both during and before actual collision events.