Campaign in US city to dim lights to prevent migrating birds from crashes

A supermoon sets behind the Philadelphia skyline (Joseph Kaczmarek/AP)

The US city of Philadelphia is dimming its lights to try and prevent migrating birds from slamming into skyscrapers and crashing onto pavements.

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