The image of a bright yellow canary in a coal mine has long served as a symbol of birds’ ability to warn us of changes in the health of our environment. The finch’s faltering song or changed behavior would signal the presence of noxious gases, and the miners would evacuate immediately.
Wouldn’t it be grand if all environmental problems could be diagnosed so simply? In fact, signs from around the globe suggest a scenario that is far more complicated. Yet evidence is mounting that birds remain valuable indicators of our environmental health.
How? They are migrating and laying eggs earlier than before. They are shifting their distribution. And in some cases, they are failing to reproduce. Evidence is growing that the avian responses are related to climate change.
The earth is naturally surrounded by carbon dioxide, methane, and nitrous oxide, so-called greenhouse gases that trap the sun’s heat. Since they warm the planet, they make life possible. We need them to survive.
But our use of coal, oil, and gas, and other activities, such as the cutting and burning of forests, is adding to the amount of carbon dioxide and other gases in the atmosphere. And the higher the concentration of greenhouse gases becomes, the more heat they trap, and the warmer our planet grows. Indeed, over the last 50 years, the earth’s temperature has risen an estimated 1°F (0.6°C).
The increase may seem insignificant at first glance, but even small changes in climate may affect birds and their habitats. A change of 1°F is enough to cause sea levels to rise, storms to become more intense, glaciers to retreat, and drought and fire to become more common. Indeed, an ice shelf larger than Manhattan has already broken free from Canada’s Ellesmere Island, and ice shelves in the Antarctic are following suit, calving and disintegrating at a significant rate.
Closer to home, you may perceive that spring is arriving earlier, fall is longer, and extreme heat days are more common. You may also notice that changes in local weather patterns correspond to changes in the birds you see in your community and even in your backyard.
As with many environmental challenges, the impacts of climate change on birds read like the rap sheet of a hardened criminal. They’re difficult to stomach. Yet the best way to respond isn’t to ignore them, but to become knowledgeable — and to get involved in conservation.
It’s also important to remember that research on the effects of climate change on birds in North America is in its infancy. Some studies lack the longevity necessary to make solid conclusions or to disclose the complexity of factors involved. Regardless, few scientists dispute humans’ contribution to climate change, the impacts it will have on the natural world, and the need to take action now. So take a deep breath, consider the facts, and become part of the solution.
For more than 70 years, no Carolina Wrens were recorded during a Christmas Bird Count in Vermont. Then, in 1975, two were spotted. After being observed sporadically on subsequent counts, the bird began making regular appearances in 1991, and its numbers increased steadily from 1999 to 2006. Once a southern species seen rarely during New England’s traditionally cold winters, the wren is now a regular. And it’s not alone. Milder winters and the earlier onset of spring have spurred a variety of species to spread their wings farther north, including Tufted Titmouse, Red-bellied Woodpecker, and Cape May Warbler.
The shift means birdwatchers stand a good chance of adding to their state lists, and it could be a boon as well to those bird populations that respond positively to increased foraging and nesting opportunities. But while warmer temperatures may expand the ranges of certain species, scientists think they may constrict the distributions of others.
The Gray Jay is one. Wildly omnivorous, it will eat anything from berries and beetles to eggs, nestlings, and carrion. Mixing morsels of food with its sticky saliva, it forms small masses, or boluses, which it caches in bark and on tree branches during summer and fall. Then, displaying an uncanny memory, it returns to the storage sites in winter.
Gray Jays live at high elevations in North America’s boreal and sub-alpine forests. Traditionally cool autumns and cold winters there have helped keep their food caches from spoiling, but warmer temperatures may now be causing them to rot. Jays hatch as early as April. Because adults rely on the caches not only to survive the winter but to provide for their nestlings, the effects appear ominous.
Biologist Tom Waite of Ohio State University and Dan Strickland, retired chief naturalist at Algonquin Provincial Park in south-central Ontario, say Gray Jay populations have declined as much as 60 percent along the southern edge of the species’ range. The researchers attribute the drop to rotting food caches and a subsequent inability of adults to feed their young. “The birds’ Achilles’ heel is the fact that they store perishable food,” says Strickland, “and the warmer temperatures are getting them in trouble.”
Diminished critical habitats
In addition to affecting southern and northern ranges of birds, climate change is also expected to diminish critical habitats. About 10,000 years ago, the last ice age left millions of shallow depressions across North Dakota, South Dakota, Minnesota, Manitoba, Alberta, and Saskatchewan. Filled with water, each depression, or pothole, came to provide a miniature environment for plants and aquatic animals, and breeding habitat for over half of the continent’s waterfowl, including Mallard, Blue-winged Teal, Northern Pintail, Northern Shoveler, Gadwall, Canvasback, and Redhead.
Temperatures in the Prairie Pothole Region have increased between 2° and 5.5°F (1°-3°C) over the last 100 years. Because of the region’s importance to waterfowl production and the vulnerability of wetlands to evaporation and drought associated with rising temperatures, the area is already closely watched by federal and state agencies and bird-conservation groups.
One of them is the National Assessment Synthesis Team, a federal advisory committee comprised of experts from universities, governments, and research institutions. Using models to analyze future impacts of climate change, they estimate that by the year 2060 as many as two thirds of the ponds located in the region will have evaporated and the number of breeding ducks will have been reduced by half.
It is challenging indeed to find a positive note in a forecast so dire, but the Prairie Pothole Region has already survived its fair share of challenges. Land managers, conservation groups, and the agricultural community, once at odds, have been collaborating in the region for years, working to protect habitat for waterfowl while maintaining the production of cereal grains. Steps are already being taken to prepare for a warmer, drier future. Ducks Unlimited, for example, is working to protect lakes and ponds, encourage conservation easements, and monitor waterfowl populations.
Climate change at sea
Every year as early as February, Cassin’s Auklets have traditionally congregated by the tens of thousands on California’s rocky Farallon Islands, located about 30 miles west of San Francisco’s Golden Gate Bridge.
As recently as 1972, the islands supported more than 100,000 auklets, but by 1989 the number had declined to 29,880. The population continued its downward spiral through the 1990s, but for as long as Christine Abrahams and other biologists from PRBO Conservation Science have been studying the colonies, they never failed to fledge chicks.
In 2005, however, this all changed. The first sign that something was amiss was the birds’ relatively late initiation of egg-laying. When eggs were finally laid in early May, it appeared that the season was underway. But by May 20, for the first time in the biologists’ memory, the auklets abandoned their eggs. A number of birds returned later in the summer and made another attempt to breed, but it failed, too.
Biologists say the immediate cause of the failure was a reduction in food availability, specifically the small crustaceans known as krill. The sapsucker of the sea, krill is a keystone species that supports the survival of other species. Found in every ocean, it is one of the world’s most sought-after prey items, sustaining not only Cassin’s Auklets but also whales, seals, squid, fish, and other seabirds. Studies of oceanic currents and temperatures identify climate change as a potential culprit.
Climate change isn’t just a terrestrial event. Our oceans are also warming, storing large amounts of energy as heat. In fact, oceans help delay the effects of warming on land and amplify the changes experienced by marine plants and animals. And the signs are being observed from pole to pole.
Even in the Southern Hemisphere, krill is an important part of the food chain. Both Adelie and Emperor Penguins, for example, swim from their colonies in search of the crustacean, which in this locale is found in a most unexpected place.
During the Antarctic winter, when temperatures plunge far below zero, a layer of ice forms around the continent. By September, the ice pack covers as much as 7.7 million square miles and shelters an incalculable number of marine organisms, including krill, which breed, find refuge, and feed on algae beneath it.
Although a layer of ice so immense might seem indestructible, researchers have discovered that the Antarctic Peninsula is warming faster than any other place on earth. The temperature of both the air and the water is rising, causing unprecedented declines in the extent and thickness of sea ice. The shrinkage has been accompanied by troubling declines in both penguin populations — 50 percent in the Emperors and 33 percent among the Adelies.
The details are too complex to untangle without more research, but scientists suspect that the falling numbers are due to the impact of ocean warming and the loss of sea ice on krill availability. In parts of Antarctica, Adelie Penguins are swimming farther from their colonies in search of krill and shifting their diets to include squid and fish, and still they aren’t finding enough food.
As many as six important colonies, including a few that have been used for 600 years, have been abandoned. And in a twist of fate that seems to mark the uncertainties of climate change, Chinstrap Penguins are colonizing the former Adelie territory. Their numbers are rising.
One of the biggest uncertainties about climate change is the effect it will have on long-distance migratory birds. How does a bird that spends much of its life in the southern part of the world know when spring is arriving to the north? For birds that have to establish territories, find mates, and build nests when food resources are plentiful, timing is key.
Consider the Black-throated Blue Warbler, a small songbird that winters in the Caribbean and breeds in the northeastern United States and southeastern Canada. It migrates more than 1,000 miles between its island home and nest site, stopping on its way north to refuel, mostly on caterpillars.
Warbler migration is widely assumed to have evolved in synchrony with peak insect availability. Earlier arrival of spring, however, may cause the availability of insects and other foods to shift as well, resulting in a mistiming of events.
Members of the Champaign County Audubon Society have been monitoring migratory birds in east-central Illinois since 1903. Their records indicate that the arrival date of the Black-throated Blue Warbler has not shifted. It has made its debut around May 5 consistently. At the same time, temperature data from National Climatic Data Center weather stations north of 40°N latitude (just north of Springfield) show that from 1912 to 2001 spring temperatures have increased, and that spring is arriving earlier. This puts the Black-throated Blue Warbler in a bind. If its migration doesn’t overlap with the peak of prey availability, it may have difficulty finding food over long distances and at its nest sites.
To complicate the matter, some migrants do appear to be adjusting the timing of their flight dates, and at other sites, even the Black-throated Blue Warbler appears to be arriving earlier. Ovenbirds, for example, are showing up in Illinois five to six days earlier. Certain long-distance migrants are being recorded on breeding grounds in New York an average of four days earlier. And a number of short-distance migrants from the southern United States are arriving an average of 13 days earlier. If temperatures continue to rise, scientists are uncertain about how much birds can adapt.
Unfortunately, this is just a glimpse of what birds may face in a changing climate. Many questions remain to be answered, yet it’s clear that we do not have a simple case of a canary in a coal mine. But we do have reason to remain hopeful.
In the late 1980s, the bird-conservation community became alarmed at the rate of habitat loss and fragmentation throughout the Western Hemisphere. John Terborgh, then a professor of biology at Princeton, published the seminal book Where Have All the Birds Gone?, and newspaper headlines heralded the prospect of silent forests.
The birding community responded, and efforts to protect habitats on birds’ breeding and non-breeding grounds increased exponentially.
Partners in Flight, an international coalition of governmental and non-governmental organizations, was formed, and new research efforts were organized to learn more about birds that travel long distances. While we haven’t vanquished the challenges of deforestation and fragmentation, we have made great progress. And we have the same ability to influence decisions about climate change.
Positive actions are already underway. Last summer’s North American Ornithological Congress in Veracruz, Mexico, included a scientific session devoted to climate change.
Conservation groups such as the National Wildlife Federation, National Audubon Society, and American Bird Conservancy are studying its effects and working to increase public awareness. Cities and states are implementing carbon-reduction programs.
Religious organizations, recycling centers, and industry are encouraging citizens to become active in reducing emissions.
And perhaps most important, the United Nations Intergovernmental Panel on Climate Change reported in January that human activity is the leading cause of climate change. Twenty-five hundred scientists from 130 countries stated that the ill effects of our actions are now incontrovertible.
Scientists agree that climate change can’t be stopped overnight because of the time lag that exists between our actions and the actions of our parents. Temperatures will rise, they say, until at least 2050, and we will continue to experience the changes we see today — earlier spring, rising sea levels, and alteration of natural communities.
Yet changes in our contribution to climate change today may make a significant impact down the road — for our children, for our grandchildren, and yes, for the birds.
Susan Bonfield is program director of International Migratory Bird Day.
Simple solutions to climate change
Around the house
Turn your yard into wildlife habitat. Draft-proof your house. Turn the thermostat down 2° in the winter and up 2° in the summer. Use compact fluorescent light bulbs. Clean or replace filters on the furnace and air conditioner. Install low-flow showerheads. Wash your clothes in cold or warm water, not hot, and dry them outside. Plant trees.
On the go
Avoid plane trips under 600 miles. Ride buses, trains, light rail, and ferries. Walk the kids to school. Use video-conferencing for business meetings.
Behind the wheel
Drive a fuel-efficient vehicle. Keep the engine tuned up and the tires inflated. Avoid jack-rabbit starts and stops, and slow down. Fuel efficiency decreases 7% for every 5 mph over 60. Switch off the motor when idling longer than 30 seconds.
At the store
Shop for home appliances and electronics with the Energy Star label. Buy locally grown and produced foods (the average meal travels 1,200 miles from the farm to your plate), and choose fresh rather than frozen.
In the community
Buy power from solar cells and windmills. Reduce, reuse, and recycle paper, glass, and metal products. Urge political leaders to raise fuel-economy standards. Support measures that reduce carbon emissions. And make your birding count; become a citizen-scientist. (See “Purple Martin Science,” page 42.)