St. Louis sits on one of the major migratory pathways of birds in North America – the Mississippi Flyway -the largest migratory pathway used by birds in North America. The flyway covers areas in Canada all the way to the Gulf of Mexico with the Mississippi River flowing underneath this highway in the sky. The Mississippi and Missouri rivers provide resources for the migrating birds as they make their way north in the spring or south in the fall during migration. The Mississippi Flyway is used by 60% of North American songbirds and 40% of North American waterfowl. That encompasses over 325 different bird species out of the 900+ species that can be found in the United States.

As birds migrate, they encounter urban and suburban environments with buildings, lights, and glass. Many birds migrate at night as this allows them to avoid predators and fly during cooler temperatures while using the night sky as a navigation tool. Bright lights in urban and suburban areas can interfere with their ability to navigate and cause them to become confused and they exhaust themselves or strike buildings in their path. A recent study by Cornell Lab of Ornithology scientists examining a combination of geography and light pollution ranks St. Louis as the fifth most dangerous city during spring migration and the 6th most dangerous city during the fall migration. Another problem is that birds can’t see the glass as we do. When foraging during the day, birds can strike glass that reflects the trees or shrubs nearby when they seek shelter. Or they may try to fly through areas that are actually surrounded by glass barriers.