Why Do Birds Keep Crashing Into New York’s Glass Towers at Night? The Answer Is Stranger Than It Looks

Every year, New York City becomes an unintended danger zone for birds passing through the region during their seasonal migration across North America. Millions of birds cross the night sky in New York City during their migration to and from their seasonal destinations in the spring and fall, depending on natural navigational aids like the stars, the moon, and the Earth’s magnetic field.

However, despite their impressive navigational skills, these birds end up crashing into buildings in the city’s dense urban landscape.

Conservation organizations and scientists estimate that up to 230,000 birds die annually in New York City alone because of collisions with buildings, according to statistics released by the U.S. Fish and Wildlife Service Urban Bird Treaty program.


According to scientists, these deaths occur because of two aspects of city living to which birds were not exposed during evolution: extensive glass structures and artificial light present in the city throughout the night.

Why Glass Buildings Confuse Birds

While glass may seem harmless to humans, it can be extremely deceptive to birds. Birds use visual cues to help them get through their environments, and glass can hinder them in a big way.

Birds, according to conservation studies cited by the National Audubon Society, tend to mistake their reflections in glass, such as reflections of the sky, clouds, or trees, for actual environments or flying routes. When they try to fly to their mistaken routes at high speeds, they crash into the glass, which appears invisible to them.

Many different types of birds pass through the city during their migrations, with more than 100 types of migratory birds flying through New York City, and many of them flying past buildings with glass windows that reflect the environments of the city.

The lighting in large cities also plays a major role in bird collision. Many bird species migrate at night because the air temperature is lower and the winds are more stable, making long-distance flight more efficient.

The birds use stars as navigational aids. However, city lighting is too bright and affects this navigational system.

According to a study by the NYC Bird Alliance, when nocturnal migrants are attracted by bright lighting in buildings, they fly in circles in large numbers. This disorientates them, making them more exhausted and bringing them closer to buildings.

Migration Seasons Are the Most Dangerous

Bird collisions are not uniformly distributed throughout the year. They tend to rise sharply during the migration periods in spring and fall, when millions of birds pass through the northeastern part of the USA.

During these periods, environmental factors like heavy cloud cover, rain, or high winds can exacerbate the bird collision issue. Bad weather forces birds to descend to lower altitudes, which makes them more likely to collide with buildings that are illuminated.

The Migration Biology Group has stated that on some nights, bird collisions can rise sharply during migration periods because of bad weather combined with city illumination.

It has been stated that bird collisions can be reduced to a great extent if conservation efforts are made during these periods.

Conservation groups and city governments have started to test solutions to make urban spaces more bird-friendly for migratory birds.

One of the more common practices is the “Lights Out” initiative, which involves asking office blocks and residential skyscrapers to turn off lights during peak bird migration nights. Research cited by the Migration Biology Group indicates that lights can be reduced to lower the number of birds lured in by city lights.

These practices have been promoted in various cities in North America because they involve easy behavioral changes rather than expensive ones.

Architectural designs also play an important part in this case. Experts from the National Audubon Society suggest that it is best to use patterned glass, etched surfaces, or non-reflective materials when planning new buildings. This helps birds identify glass as an obstruction rather than an open space.

A Growing Urban Wildlife Challenge

In fact, bird strikes with buildings have come to be regarded as one of the most critical human-related hazards to migratory birds in North America. According to scientists, bird strikes with buildings are a good example of how contemporary urban planning can, in a manner of speaking, pose a danger to wildlife that long predates man-made developments.

Yet, as with most problems, the study that identified the issue also points to the solution, with conservationists stating that a series of lighting policies, bird-friendly architecture, and education can significantly help to curb the deaths.

For a city like New York, which borders a migration route, such changes could help to ensure that millions of birds can continue their passage safely through the night sky.