Cut light pollution and treat glass to help migrating birds, say researchers

Spring bird migration has begun. Under cover of darkness, 2.5–3.5 billion birds will fly northward to their breeding grounds in the United States and Canada. According to the Cornell Lab of Ornithology, now is one of the most important times of year to keep birds safe by reducing non-essential lighting at night and treating window glass so birds can see it and avoid deadly collisions.

"Up to a billion birds die each year in the United States when they crash into windows and other structures made with reflective or transparent material," said Andrew Farnsworth, a visiting scientist at the Cornell Lab of Ornithology.

"Numerous studies have shown that light attracts and disorients birds as they migrate at night. They're drawn closer to buildings where they collide with glass. One billion birds killed annually in collisions means approximately 30 birds die from window collisions every second in the U.S."

To help prevent collisions, turn out non-essential lighting from 11:00 p.m. to 6:00 a.m. or draw curtains to keep light inside. Add shields to external lighting to direct light downward and out of the skies. Taking these steps from February 15 to June 15 will save birds during spring migration. Reducing light pollution year-round will benefit wildlife, human health, and energy savings.

Stopping bird collisions also means making glass safer by day. Birds don't see glass as a solid surface and can fly into it at full speed, often resulting in injury or death. Making glass visible includes breaking up reflections of sky trees and other vegetation. Simple window treatments may include decals or cords spaced 2 inches apart on the outside of the glass.

A 2014 study estimated that most bird-window collisions in the U.S. occur at residences and low-rise buildings. Once treated, your windows will be safe for birds all year round.

Migration studies from the Cornell Lab and partners have found:

• Birds attracted by the glow of artificial light at night are drawn into areas where they are also exposed to higher concentrations of airborne toxic chemicals.
• In the Western Hemisphere, nighttime light pollution levels are increasing the most in the southeastern United States, Mexico, and Central America.
• Mass bird deaths at a building studied in Chicago could be reduced around 60% by decreasing lighted window areas.
• The BirdCast website forecasts nightly levels of bird migration up to three days in advance. Its Migration Dashboard reveals how many birds are overhead on any given night, right down to the county level.

"It's such an exciting season, with birds migrating through neighborhoods all across the U.S. and Canada to their summer breeding grounds," said Julia Wang, a Cornell Lab of Ornithology project leader who's been working on Lights Out efforts. "If we do our part to turn out lights and make glass safer, we can give birds the best chance to survive, make it safely to their destinations, and raise the next generation."