Have you ever thought that you heard birds chirping overhead in the middle of the night? You were not imagining it: during migration, thousands of birds will be chirping and peeping to one another to stay in touch.
Birds have been migrating vast distances for millennia. They are guided by the constellations, the moon, prominent land and water features, and the magnetic pull of the Earth. Their journeys are the stuff of legend – the extinct Passenger Pigeon once dominated the sky as millions of birds passed overhead, actually obliterating the sun by their sheer numbers.
Each spring, neotropical migratory birds leave their winter feeding grounds, from the southern United States to the tip of South America, and fly north to their summer breeding sites. It's magical to see flashes of colour and hear the bursts of song that erupt from trees newly leafing out.
Each fall, when the young outgrow the nest, and insect populations dwindle, the birds return to warmer climates where food is abundant. Seed-eating birds, such as chickadees and juncos, move in from more northerly locales to gain access to food that will carry them through the winter.
Some migrating birds must fly thousands of kilometres along ancient migration routes or "flyways" to reach their destinations. The four major flyways in North America are: the Atlantic, Mississippi, Central and Pacific Flyways (see map above).
Tragically, many birds do not complete their journey. Natural forces such as inclement weather and wild predators take their toll. As we humans continually alter and pollute the landscape, laying waste to bird habitat or diminishing its value as foraging territory, migrating birds are forced into inhospitable areas where they are vulnerable to pesticides, predation by cats, or collisions with windows and buildings that are lit at night. The tightly clustered office towers of large metropolitan centres such as Toronto are a major hazard for migrating birds, as FLAP data (from almost two decades of bird rescue patrols) have shown.
Added to these threats to bird survival is the steady plundering of the Boreal Forest, the breeding ground for multitudes of songbirds. As more and more of the Boreal Forest falls to lumber or mining companies, birds and other animals are squeezed out of their natural habitat and perish as a result.
Migratory birds who make their homes in forests, wetlands, tundra and meadows will not adapt to the changing landscape quickly enough to ensure the long-term survival of many species. This is especially true in the urban environment dominated by lights, concrete and glass. In this bleak landscape, their food is in short supply and they are confused by night lighting (particularly at high altitudes). What's more, birds have no concept of glass which leads to often-fatal collisions with windows.
We encourage everyone who cares about birds to get involved. Contact your municipal, provincial, state, or federal representatives to ensure that they understand the issues affecting migratory birds. Urge them to adopt bird protection policies that prevent bird collisions with buildings, as Toronto, Calgary, San Francisco and other cities have done.
Click here for bird migration facts and the answers to some frequently asked questions.
Click here to find out how to track bird migration at night with weather radar.