Collisions with buildings have become one of the leading causes of this mortality, especially due to the extensive use of glass surfaces in these structures. This is because by reflecting the sky, trees, or surrounding vegetation, these facades create the illusion of a continuous habitat. Every spring and fall, millions of migratory birds cross the American continent along major natural corridors known as flyways. These flyways connect ecosystems, economies, and cultures from the Arctic to Patagonia, stretching like invisible highways over mountains, rivers, and coastlines and guiding the movement of entire flocks across the continent.    Although some species undertake extraordinary nonstop flights, for many others migration occurs in stages, with successive stops to rest and refuel; in fact, the cumulative time spent at these stopover sites can exceed the total time in flight. But when these stops occur in urbanized landscapes, birds must face additional obstacles and threats.…