The two beams of light which shoot out of Lower Manhattan every year in tribute to those killed in 9/11 risk the lives of around 160,000 birds annually, according to a study. The birds are drawn to the lights and are pulled off course from their yearly migration, according to The New York Times, which can leave them exhausted, starving, or injured. The scientists say the birds call to each other as their confusion increases. Scientists have been working to reduce harm to the birds since 2005. When they estimate the number birds trapped by the light reaches around 1,000, the lights are switched off for 20 minutes to give them time to escape. Sara Crosby, who's part of an N.Y.C. group which monitors the streets for birds that have died after crashing into buildings, told the newspaper: “I was here for 9/11. I saw the second plane. I am not ‘anti’ a tribute ... But a tribute that kills thousands of birds? Is this really what we want?”