Philadelphia calls for 'lights out' to help nocturnal migrants

Bird Safe Philly has announced the 'Lights Out Philly' initiative, a voluntary programme in which many external and internal lights in buildings are turned off or dimmed at night during the spring and autumn.

The coalition, which includes Audubon Mid-Atlantic, the Academy of Natural Sciences of Drexel University, the Delaware Valley Ornithological Club and two local Audubon chapters, was formed after the city's largest mass-collision event in 70 years was reported last October, during which many hundreds of dead birds were found around the city.

Common Yellowthroat migrate at night along the Eastern Seaboard (Alexander Viduetsky).

The Lights Out Philly programme runs from 1 April to 31 May and from 15 August to 15 November. Property managers and tenants are asked to voluntarily switch off lights between midnight and 6 am, especially in a building's upper levels, lobbies and atriums.

Birds navigate during migration using celestial cues and when they cannot see stars on a cloudy night they get confused by bright city lights. Windows pose a problem, because birds might see a reflection of trees or the sky. Scientists estimate between 365 million and 1 billion birds are killed by collisions with buildings or other outdoor structures in the US every year and those crashes are taking a toll on some species.

Common Yellowthroats, White-throated Sparrows, Grey Catbirds and Ovenbirds are the most common victims in Philadelphia – species that are also threatened by the climate crisis and other predators.