Spring Is in the Air—So Are Migrating Birds

Here in Baltimore and beyond, spring means temperatures warming, flowers blooming—and birds flying overhead as they return to their breeding grounds. Every spring, an estimated 3.5 billion birds migrate back into the United States from their southern wintering grounds, according to the Cornell Lab of Ornithology. These birds are in search of nesting locations for breeding season and flourishing food sources, such as insects.

As temperatures drop and food resources decline later in the year, the same birds you see flying overhead now will embark on their fall migration and travel back south to their non-breeding grounds for the winter. Many, but not all, bird species migrate; according to Cornell, of the more than 650 species of North American breeding birds, more than half are migratory.

Many birds travel thousands of miles in their biannual migrations, oftentimes following the same path every year. Birds that are making the springtime northern trek for the first time often know exactly where to go—despite never having made the journey before. Scientists still don't fully understand how these navigational skills are so precise, but it's believed that birds use the sun, stars and the Earth's magnetic fields to complete their migrations.

For some species, migration pathways are dependent on locations that provide food sources along the way, which are vital to the birds' survival on their arduous journeys. For example, the rufa red knot flies more than 9,000 miles during its springtime migration from South America to the Canadian Arctic; during their trip, they stop by Delaware Bay beaches to feast on horseshoe crab eggs, which give them the fuel necessary to complete their migration north.

Migratory species of birds face many natural challenges during their travels; long distance migrations are physically grueling, and there's always a risk of encounters with predators and bad weather. But there's a human-induced threat as well that has become increasingly deadly for migrating birds. More than 1 billion birds die in North America every year after colliding with buildings, mostly during spring and fall migration and mostly in cities, such as Baltimore.

Birds migrate at night and become drawn to and disoriented by the white and yellow lights in cities, which mimic the light of the moon and stars that they use to navigate. After roosting overnight in city trees, they fly from tree to tree at sunrise. Sometimes these birds collide with buildings when they become confused by the reflection of trees on exterior walls, or they see vegetation inside buildings.

The good news is that you can help if you find a stunned bird on the ground in the Baltimore area—just contact Lights Out Baltimore to report your sighting. There are also steps that homeowners and businesses can take to lower the risk of bird strikes occurring in the first place.

Homeowners who have trees across from their windows can move bird feeders 5 feet or closer to windows, and businesses can turn off all non-essential lights at night to lessen the white and yellow lights that attract migratory birds during their nighttime flights.

Businesses can also apply a patterned film—like the one found on the National Aquarium's main building and Animal Care and Rescue Center—to the reflective exterior windows of their buildings, which interrupts the glass' reflection to deter bird collisions. Businesses can also change their exterior lighting to cool colors, like green and blue, which don't attract or confuse migrating birds.

Another easy solution to reduce disruptions to migrating birds is to prevent exterior lights from sending light skyward by pointing them in a downward direction. Adding a shield or dome to exterior fixtures will also prevent light from spilling skyward.