Birds have been around for at least 100 million years—an incomprehensible span of time, especially when we consider that the first human ancestors only appeared about 3 million years ago. We don't know for sure when those ancient birds first began to migrate, but fossil evidence suggests that birds were making extensive seasonal journeys by about 40 million years ago.
It's likely that humans have hunted migratory birds since very early in our history, and for indigenous people in the northern latitudes, migratory birds are still an important source of food. Winter is often a time of scarcity in the boreal forest and arctic, and by early spring food may be critically short. Imagine the joy and relief when the protracted silence is broken by arriving flocks of ducks and geese. These birds could literally mean the difference between security and starvation.
Some Athabaskan Indian elders living in the boreal forest of Alaska can remember difficult years when people survived by eating songbirds that arrived in the early spring. This happened when a hard freeze came late in the season, and songbirds froze to death on their perches. Hungry people walked around on the crusted snow, checking the bare spots under every tree, where they found the little feathered bodies. Back in the camps or settlements, songbirds were boiled to make a nutritious lifesaving soup.
Still today, hunting and gathering people in the far north depend on the predictable migration of birds, much as their ancestors have done for thousands of years. By far the most important are waterfowl—like Canada geese, black brants, mallards, blue-winged teal, and pintail ducks—that come north with the melting snow and thawing ice. Above all, they are treasured for their rich and delicious meat, but people have sometimes used their feathers for clothes and bedding, and they might also collect eggs in the nesting season.
Of course, today many non-native people hunt ducks, geese and other migratory birds for food and sport. And it's big business—according to a US Fish and Wildlife Service (USFWS) survey in 2006, migratory bird hunters spend 1.2 billion dollars annually.
Hunting is not the only economic benefit from migratory birds. The 2006 USFWS survey revealed that bird watching brought about $36 billion dollars into the U.S. economy. One in every five Americans is a bird watcher these days—that's 48 million people!
For many of us, we'd be hard pressed to put a dollar value on the beauty of these amazing creatures. Our days are brightened beyond measure by seeing a robin coax a worm from the front lawn; listening to a morning chorus of thrushes and warblers announce a spring morning; watching the whir and shimmer of a ruby-throated humming bird at a summer feeder.
During the unimaginably long history of migratory birds on earth, there have always been places for them to nest in the summer, places to overwinter, and places to rest and refuel along their migratory routes. In this way, the life of every bird is like a tapestry spread across the face of the earth—sometimes covering only a small area, sometimes encompassing whole oceans and multiple continents. The specific design of this tapestry may have changed with the earth's shifting climate, as forests spread or retreated, glaciers expanded or diminished, waters spread or decreased. But until very recent times there were no man-made losses of habitat or impediments to flight.
When humans appeared on the scene, it was people who depended on migratory birds for survival. But the tables have turned…and now, more than any other time in history, migratory birds are dependent on humans for their survival. And the choices we make are impacting the future of many migratory birds.
Every year, agencies and researchers from throughout the U.S. collaborate on a "State of the Birds" report that examines the current status of birds. The 2011 report concludes that of the nation's 800 bird species, nearly one-third are endangered, threatened or in decline.
Let's look at some of the major difficulties facing birds today.
Perhaps the biggest threat to the long-term survival of migratory bird species is habitat loss. This includes nesting grounds in the northern boreal forests and other places throughout the world, overwintering areas from the southern U.S. to the tropics, and stopover areas along migratory routes on several continents.
Some species are already in severe decline because they have lost essential areas like forests or wetlands where they rest, feed, or raise their young. Birds arrive starving and exhausted after flights of hundreds or thousands of miles, but in some places their food source is no longer available or the places where they have always landed are now gone.
For example, red knots returning from Brazil stop in Delaware Bay (between Delaware and New Jersey), where they feed on the eggs of horseshoe crabs to replenish their diminished and exhausted bodies. But commercial fishing has greatly reduced the crab population and red knot numbers have declined—so much so that in 1996, Audubon and other organizations petitioned the US government to list them as an Endangered Species.
One of the great long distance migrants—bar-tailed godwits—travel in spring from New Zealand to their breeding grounds in the Artic. To make this epic journey, these northbound migrants must stop to rest and feed in wetlands along the coast of Asia. But intensive development has taken away half of these crucial wetlands and only 10% of those remaining are not slated for future development. So bar-tailed godwits will face losing 90% of the wetlands that have made their long journey possible every spring.
Habitat loss is not limited to distant continents. Here in the United States, 1.2 million acres of potential wildlife habitat—croplands, pasture, and grazing lands—are lost each year to developments such as expanding cities and suburbs, industrial and commercial complexes, and highways.
The boreal forest stretches across 1.5 billion acres in North America. Billions of birds, belonging to more than 300 species, nest and raise young there every summer. This vast northern forest is critically important, not only for wildlife habitat but also for regulating greenhouse gases, yet it is largely unprotected. In fact, already, more than 30% of the North American boreal forest is scheduled for development.
In the tropics, deforestation is widespread. From the original 6 million square miles of tropical rainforest, less than half (2.6 million square miles) remains, and that remainder is disappearing at a rate of 5 to 10 percent per decade, according to The Nature Conservancy.
One of the most interesting forms of tropical agriculture is shade-grown coffee plantations. Many species—including familiar North American backyard songbirds—thrive on these traditional farms. But newly developed coffees are grown in full sunlight, so the shady forests essential for wintering birds are being cut down. Today, even the largest buyers of coffee beans only use shade grown coffee in a small percentage of their coffee products, if at all. But we can vote with our pocketbooks. Every time we buy or drink coffee, we can help the birds by asking for shade-grown varieties.
We can help migratory birds in other ways, too. For example, runoff from herbicides, pesticides and fertilizers affects many habitats that are important to birds and their growing young—forests, farmlands, wetlands, rivers, and lakes. Even lawn care products can be harmful for birds that feed in our yards or nest nearby.
Small decisions we make each day can help to bring the color of birds and the beauty of their songs into our lives.
The numbers of birds killed each year in the U. S. by collisions with man-made objects is staggering: power line collisions, entanglements, and electrocutions—170 million; communication towers—50 million; wind turbines—400,000.
A large number of these deaths occur during fall and spring migration periods, especially at night.
Perhaps the biggest toll on migratory birds comes from tall buildings and glass fronted buildings—in daylight, birds can't tell the difference between real and reflected scenes of sky, trees, brush. And as we'll see, at night, these buildings cause other problems for migrants.
Many birds navigate at night, using the position of the moon and stars to stay on course. Just as it does for people, light pollution from cities and towns can make the sky difficult for birds to see or the swarms of artificial lights become confusing, especially in wet or foggy weather. Migrating birds are attracted to the light and will circle a building or flutter against it, until they fall from exhaustion. On a single night, hundreds or sometimes thousands of birds are either injured or die around a tall, brightly illuminated building.
What can be done? In Toronto, Ontario, volunteers are on the streets before dawn at migration times, picking up exhausted or injured birds and caring for them until they can be safely released.
Some cities are working on the source of the problem—turning lights off for all or part of the night during fall and spring migrations. These light's off programs that reduce "sky glow" have a bonus effect…people can see more of the night sky, the moon, and the stars. And of course, companies and governments are saving money on power costs.
One of the best success stories comes from a downtown Chicago area that darkened buildings during fall migration—reducing bird fatalities by 83%!
Another promising step is a bill before the U.S. Congress. This legislation, called H.R 1643, The "Federal Bird-Safe Buildings Act", would require new, purchased or remodeled federal buildings to incorporate bird safe designs.
There is serious and widespread concern among biologists that habitat changes caused by a warming climate will severely impact migratory bird species. For example, we might think migratory waterfowl such as geese and ducks that raise their young in the northern forests would benefit from the longer summers. But as temperatures rise, the lakes and ponds that these birds depend on are shrinking and drying out.
In the oceanic world, rising sea levels, shifting food sources, and other changes to marine ecosystems will impact many species of seabirds, shorebirds, and waterfowl.
Scientists predict a wide array of changes that will affect hundreds of bird species in countless ways throughout the world. Because the lives of migratory birds often span entire continents and oceans, they will be among the animals most profoundly affected by our warming climate.
For literally millions of years, migrating birds have brought a flood of color and sound to the awakening land. People of many cultures have awaited their arrival and have listened for the messages in their songs. Perhaps today these voices bring not only beauty but also a lesson: As we take care of the birds' world, we are also taking care of our own.
Alaska Department of Fish and Game
American Bird Conservancy
Audubon Water bird Conservation: Issues and Answers
H.R. 1643 Federal Bird Safe Building Act of 2011
Migratory songbirds and cats
Nature Conservancy's Migratory Bird Program
Shade Grown Coffee and Migratory Birds
The State of the Birds 2011
US Fish and Wildlife Service
USFWS Migratory Bird Program