Results Show Lights Out Philly Works

With millions of birds packing their bags in preparation for peak spring migration through the Philadelphia region starting April 1, it’s time to break out the binoculars, get outside and look up.  

Birding is the most popular sport in the U.S., with over 51 million people birdwatching in their backyards, state parks and even birding competitions. While Mother Nature’s spectacle is beautiful and amazing, it’s not without perils for the birds. 

Each year tens of millions of birds wing through the region in spring and fall while migrating between their breeding and wintering grounds. Unfortunately, many never make it because they are killed when they fly into buildings, confused by the artificial lights and glass.

Philly street scene in October 2020. Photo by Steve Maciejewski/Audubon

A mass collision of thousands of birds in downtown Philly on Oct. 2, 2020 prompted the formation of Bird Safe Philly to advocate for measures to reduce the number of collisions. 

In April 2021, Philadelphia joined the national Lights Out initiative. Since then, more than 100 commercial, residential and municipal participants in the Philadelphia region have joined in turning off lights at night to help prevent bird collisions. 

So how are we doing? 

While still in the early stages and with limited data, Lights Out Philly has already begun to see the positive effects of turning the lights off. At one monitored building where artificial light has been reduced the most (Atrium building in the courtyard of the BNY Mellon Center, 1735 Market St.) fall collisions have declined by 70% since 2020. More years of monitoring in Philly are needed, but long-term monitoring and data analysis in Chicago has proved that Lights Out worked there to reduce collisions. 

Credit Anwar Abdul-Qawi/ANS

What is Bird Safe Philly? 

Bird Safe Philly was formed in 2020 by the Academy of Natural Sciences of Drexel University, Delaware Valley Ornithological Club, and National Audubon Society — Audubon Mid-Atlantic, Wyncote Audubon and Valley Forge Audubon. Bird Safe Philly — in collaboration with the City of Philadelphia Office of Sustainability, BOMA Philadelphia, and Building Industry Association of Philadelphia — initiated Philadelphia’s first Lights Out program in April 2021 as a primary way of preventing bird collisions caused by artificial light at night. 

Bird Safe Philly volunteers monitor downtown areas for dead and injured birds that have collided with buildings and collect data through the iNaturalist website and app. Dead birds are sent to the Academy’s Ornithology Collection where they are prepared for future study. Injured birds are taken to rehab. 

Why is Philadelphia important to migratory birds? 

Over 250 species of birds occur in Philadelphia annually, and 70% of these are migratory species. Scientific studies indicate the number of migrants that occur annually could exceed 50 million individuals. 

What dangers do migratory birds face here? 

One of the biggest threats to migrating birds is collisions with buildings, transit shelters, glass walls and other structures. These collisions are caused mainly by glass and/or by artificial light at night and are estimated to kill up to a billion birds annually in the U.S.; up to 42 million in Canada. 

What impacts are these collisions having on birds? 

Bird collisions are now considered a major conservation issue throughout the world and one that has contributed to the loss of 3 billion birds in North America (about 30% of North America’s birds) since 1970. Some species are more susceptible to collisions than others, and many declining species, like the Golden-winged Warbler and American Woodcock, are highly susceptible to collisions. 

Preparing birds for research in Conversations With Birds exhibit. Credit: Ramon Torres/ANS

When do these collisions occur? 

Birds collide with structures throughout the year, but in urban areas the largest number of collisions occur during the spring and fall when bird migration peaks. Collisions can also occur any time of the day or night, but collisions involving actively migrating birds tend to peak from late at night until just after dawn. 

Which species are affected by collisions? 

As of 2023, 284 species of birds have been documented colliding with buildings in the U.S. and 119 species have been documented colliding with buildings in Philadelphia since 2008. Warblers (30 species and 48% of all individuals) and new world sparrows (nine species and 21% of all individuals) make up the largest percentages of the birds that have been documented colliding with buildings in downtown Philadelphia since 2008.  

What types of human structures do birds collide with in Philadelphia? 

Birds collide with structures of all kinds, but collisions occur mainly at those with large amounts of glass and/or artificial light at night. 99% of all bird collisions in the U.S. occur on residential homes one to three stories tall and low-rise buildings four to 11 stories high. This is because those buildings are more numerous than high rises. Collisions at high rises get more notoriety because they are more visible, easier to document, and can result in the deaths of thousands of birds. 

Philly skyline on a regular night. Credit Victoria Sindlinger/Audubon

How can collisions be prevented? 

Collisions can be prevented by reducing or eliminating artificial light at night and by placing patterns or physical barriers on or in front of windows and other glass surfaces to discourage birds from trying to fly through them.  

What has been done to prevent collisions from occurring in Philadelphia? 

Since 2008, Audubon Mid-Atlantic has raised awareness of the problem through education, monitoring, research, advocacy and collaboration with others including the Academy. Audubon constructed the Discovery Center (2018) and John James Audubon Center (2019) to be collision-free buildings, and the Academy continues to offer exhibitions and programs to increase awareness of the issue. With the launch of Lights Out Philly, the effects of nighttime artificial light began to be addressed for the first time.  

A final note 

While Lights Out Philly can help reduce bird-building collisions, it cannot prevent collisions caused by glass and other reflective or transparent surfaces that continue to occur during the day. The proliferation of new buildings in and around Philadelphia with mostly glass facades will only increase the number of bird collision deaths that are being caused mainly by glass. 

Visit our Conversations With Birds exhibit on view through May 21.


  1. Isn’t there some kind of sound that birds would find scary or unpleasant enough that they would veer away from it? I would think small window-attachable speakers could run during the month or three of the greatest problem, and the combination of height and directionality could allow the sounds to have sufficient power to achieve the goal without having a negative impact on humanoids!
    – MJM

  2. Is it possible to have a recording sound of “bird of prey” near by where when the bird come close they will think a bird of prey is near by and won’t approach the lights? Ornithologists use a “pish” sound when they want to attract birds but don’t use it when they want to keep birds safe.
    Maybe a sound can be added to give birds a scare feeling like there may be a bird of prey around.

  3. It is best to put of the light during the migrations of the bird species, the bird conservation society to inform the city authority, only during the month of bird migration.
    Hais Wasel
    Larry Butterfly conservation Habitats Papua New Guinea

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