This week, bird advocates are asking Connecticut residents and property managers to turn off their lights as the peak of summer songbird migration approaches. Over 500,000 birds are expected to cross over Long Island Sound into the state over the remainder of the week, most of them flying by night.

"It's literally peak migration right now," said Meredith Barges, Yale divinity school student and co-chair of CT Lights Out, an environmental advocacy group. "This time of year people probably hearing birds all around them."

The charge to turn off lights is led by Lights Out CT, the Connecticut Audubon Society and other environmental groups. They say that turning off your lights between 11 p.m. and 6 a.m. can do a lot to protect birds during the peak of migration season.

"They migrate on nights when the weather conditions are favorable... when winds from the southwest can give them a boost flying up from the south" said Tom Andersen, spokesperson of CT Audubon. "As they are flying, they are attracted to lighted buildings. It can distract and disorient them. It can lead them into buildings where they crash and die."

Between late March and early June, billions of birds will fly up the East Coast by night. Some are coming up from the American South and islands in the Caribbean. Others, like the bobolink, are flying from as far away as the Argentinean plains. Many of these birds will settle down in New England for the season but many more, particularly sea birds, will bounce all the way up to the Arctic. Most of this migration occurs at night when birds are safer from predators.

"The night sky is not respected or protected," said Barges. "We don't understand that a lot of life, a lot of important work is done at night... We just don't see it, literally, so we don't value or respect it."

According to BirdCast, a national ornithological research and bird tracking organization, over 2.7 million birds crossed into Connecticut on the evening of May 15. Over 900,000 birds entered the state between 8 and 9:00 pm. These birds were tracked by radar, registered by the same technology that tracks weather and include dozens of species like the Scarlet Tanager and Magnolia Warbler.

"On a high bird alert night it's generally estimated that we'll have around 500,000 birds," said Andersen. The next high migration night is forecasted to be on Thursday May 18. In the days after each high migration night millions more birds will be flittering around Connecticut. Over the weekend the CT Audubon is holding various bird migration events. "We call it Migration Madness," he said.

The biggest threat facing these birds on their trip are brightly lit windows, experts say. Nocturnally migrating birds are instinctively drawn to and disoriented by bright light. Millions of birds will die this year because they have crashed into lit windows during the migration season.

In the evolutionary history of migrating birds, bright light at night is a relatively recent phenomenon. It's not clear why birds are drawn to light but it likely has something to do with how birds navigate and orient themselves for nocturnal migration.

A 2017 study published in Proceedings of the National Academy of Science found that bright lights are so effective at attracting birds that in the presence of bright spotlights birds wont stop flying but will try to remain near light sources. The 9-11 Museum's "A Tribute in Light" instillation collected enormous swirling clouds of birds at night.

"Birds are caught in the lights and they circle inside them," said Barges. "When they dim the lights, the birds release out into the sky. So light both attracts and captures birds because they are using cues in the natural environment, like the light of stars, to navigate. Light pollution blocks these cues and also attracts and traps them."

Many cities have adopted bird-safe building ordinances in response. Connecticut is currently considering a bill, HB 6607, that would mandate state-owned buildings turn their lights off between certain hours. This would save on utility bills while protecting nocturnal life. Barges explained that light pollution was one of the few kinds of pollution that can be turned off instantly.

"It's a really cool thing you can do instantly," said Barges. "You can immediately get rid of it by turning off your lights."

But there's still a lot of work to do, says Barges. She's working on the Yale Bird Friendly Building Initiative to make buildings nationwide more bird safe and ecologically friendly. She hopes she can target self-storage facilities next as light polluters.

"All the self-storage is massively lit up and nobody is inside there at one o'clock at night," said Barges. "It would be good to call those guys out."