Douglas Stotz, the Field Museum’s senior conservation ecologist, says that two of the biggest killers of migratory birds are lights and windows. Birds rely in part on stars and constellations to find their migratory routes, while artificial illumination, including indoor lights behind deadly glass windows, can confuse them and lead to fatal crashes. (Stotz points out that even humans occasionally walk into glass doors — and we interact with glass every day.)

In 2017, in an effort to better understand how lights affect bird movements, Cornell University researchers alighted upon the massive twin light beams of New York’s 9/11 memorial. Monitoring birds via radar, the researchers found that the number of birds over lower Manhattan was up to 150 times greater when the lights were activated.

In other words, it seems that an ever more artificially constructed and anthropogenically  illuminated environment is a veritable death trap for many birds.

So, what can be done?

Recently, conservation groups have moved forward to implement efforts designed to reduce collisions, including improved methods for monitoring and predicting peak migrations, and then getting building complexes to turn out their lights during those periods.

Chief among these efforts is the Audubon Society’s Lights Out program. Over the last two decades, the movement has established “delumination” agreements in almost 40 cities. These programs, typically involving specific buildings or complexes, are largely voluntary, while some Lights Out agreements also include city or county-level ordinances for government-owned buildings.

In 2017, Galveston, Texas, saw nearly 400 birds die from collisions with a single building in a single night. Such staggering fatalities are not unprecedented in Texas, which is home to the second (Houston) and third (Dallas) deadliest cities nationally for birds by collision mortality, after Chicago.

The Lone Star State has recently stepped up as a champion of Audubon’s Lights Out program. In 2021, Fort Worth became the first major Texas city to sign on to the Audubon Society and Cornell University’s Lights Out Texas campaign, after which several other counties followed suit. The Texas Conservation Alliance, an organization that educates Texans about wildlife and advocates for habitat improvement, is planning to monitor collisions in Fort Worth — which would make it the sixth city in a major collision hotspot to collect specimens to help better understand the dynamics of when and why birds crash.

But such programs are piecemeal, voluntary initiatives. Says Stotz, “The long-term solution is not Lights Out.” Rather, he posits, the answer lies in smarter construction.