AUSTIN—Millions of birds slam into buildings, wind turbines, and other structures every year—a problem that could be lessened by erecting “acoustic lighthouses” to warn them of their impending doom, according to a study presented here today at the annual meeting of AAAS, which publishes Science. People have tried warning birds with things they can see, such as window markings and lights, but that doesn’t always work. One possible explanation: Birds’ eyes don’t face forward when they’re flying, leaving them with a gaping blind spot directly in front of them. So scientists hatched the idea that sound may be a better warning signal. They trained 16 captive zebra finches to fly through a flight corridor roughly the length of a bus. Sometimes the birds were free to fly the full length, but in other trials, they encountered a mesh net that gently caught them (the benign equivalent of a building strike). The birds slowed down as they approached the net, but they slowed down even more—by an additional 20%—when they could hear a loud sound 1 meter before hitting the net. Sound alone didn’t cause the birds to slow down, so the team thinks that the “acoustic lighthouse” caused birds to be more alert and notice the net faster than they would have otherwise. Changes in their flight posture support this idea because birds flew more upright after hearing the sound. The study, published in Integrative and Comparative Biology, shows that fewer birds may bludgeon themselves on buildings if we play a siren and flash a warning light.