Each spring, from mid-April through May, massive numbers of birds flock northward for food and breeding.
“This is the time of year that birders live for...we're going to see millions of migratory birds passing over Washington state,” said ornithologist Tim Billo, a teaching professor at the University of Washington. “Every day there are going to be surprises in your yard.”
Much of that migration happens at night. Billo said migratory birds have evolved to travel hundreds of miles under the cover of darkness, avoiding predators and leveraging cooler temperatures for efficient flying.
“It's these small birds, songbirds and shorebirds, that are migrating at night,” he said. “They rely on cues such as the stars and the moon to navigate.”
But bright lights from homes and buildings disorient the birds, Billo said, and they cannot see the stars and moon as well.
“They can fly across the Gulf of Mexico, but then they get here and they end up attracted to our cities because of lights,” Billo added. “Something that seems simple to us, like a glass window…it's incredibly deadly to them.”
A student research project on UW’s Seattle campus found crows prowl the base of windows, scavenging the dead birds that hit them.
The only hazard that kills more birds than windows is cats. Wind turbines also take a toll.
What can we do?
One of the most important ways to protect birds is to keep cats indoors. Cats kill billions of birds each year in the U.S., according to research from the Smithsonian and U.S. Fish and Wildlife Service.
There is a simple solution to protect birds from windows as well, said Joshua Morris, the conservation director at Birds Connect Seattle (formerly called Seattle Audubon).
People and companies can add translucent dot stickers to their windows to help birds see and avoid the glass.
Morris helps run a bird collision monitoring team that tracks the number of birds hitting windows in Seattle. They estimate 80,000 fatal collisions during migration season happen at homes in Seattle.
“That's not looking at things like institutional buildings or educational campuses or skyscrapers, just homes. So it's a staggering scale of mortality,” Morris said.
On busy migration nights, people may want to take extra precautions, such as turning off all non-essential lights outside. “Lights Out” campaigns suggest doing so between 11 p.m. and 6 a.m. Warm-colored lights (under 3,000 Kelvins) also tend to be better for the birds.
To further help migratory birds, Washingtonians can plant native vegetation in their yards to create safe and enticing rest stops, Morris said. Such habitat can provide nectar and insects for birds to fuel up along the way.
Witnessing migration
At night, migrating birds are flying a few thousand feet up, Morris said. That is too high to see small songbirds, but sometimes you can hear them. And people can see migratory flocks taking off at dusk, from places like Grays Harbor.
In lieu of actually seeing the massive overnight migration, birders often use Cornell Lab of Ornithology’s BirdCast site. That team uses weather radar to help track the busiest migration nights.
“Essentially, the same technology that we use to track cloud cover can track the movement of birds,” Morris said.
