Bird-window collisions: a global review

Up to one billion birds are estimated to be annually killed by collisions with glass panes in North America alone, which is one of the major causes of bird deaths due to anthropogenic causes. However, little attention has been given to this problem, especially in the tropics, and more research has been published only in recent years. Thus, we aimed to review the factors that cause collisions of birds with glass panes in the indexed bibliography, as well as mitigation solutions. There is a large concentration of papers published in the broad scientific literature in the Northern Hemisphere. It is difficult to extrapolate these findings to the rest of the world, since many factors are local-specific on a greater or lesser scale. The main factors influencing rates of mortality by collision with glass panes were large areas of continuous glass, vegetation very close to panes, passage of migratory species, presence of feeders, abundance and behavior of birds. The application of stripes or other patterns that cover the glass evenly, or external use of curtains and paracords, were effective methods to mitigate the collisions. It is necessary to reach citizens in order to really solve this problem. They must be warned about the risks that their windows represent to birds and let them know about the suitable mitigations. Further studies in the tropics are also needed to generate data that support appropriate public policies.