Philadelphia is about to go completely dark at night. Here’s why

Sharon Villines

The headline is more dramatic than the actual practice which only affects commercial buildings interior lighting, but the article contains a lot of data on how many birds die from lights left on at night.

On a single night in October 2020, more than 1,000 birds crashed to their deaths against the windows of tall buildings in downtown Philadelphia. Blamed on a rare convergence of the semiannual migration period and bad weather, a major contributing factor was the abundance of lights left on inside tall buildings overnight. By the next morning, the streets were littered with dead birds.

“There were just hundreds of birds everywhere. It was like nothing we had ever experienced,” says Keith Russell, program manager for urban conservation at Audubon Mid-Atlantic, the regional office of the national bird-focused nonprofit. The group had been calling on building owners in the city to do something about bird collisions since 2006 and had been conducting regular counts of bird deaths in the city since 2008, but not much had changed.

David Oesper

Thanks, Sharon. Birds colliding at night with communication towers is a big problem, too. Flashing lights instead of steady lights are less likely to attract night-flying birds towards the towers.

Any dark-sky community won't have to worry about tall buildings, but nearby communication towers can be a big problem. Slowly-blinking red lights are much less obtrusive for astronomy than white strobes.