Due to drought and development, Red-crowned Cranes are having trouble breeding in their native wetlands in Asia. The drought is believed to be a result of climate change. Photo: David Courtenay/Audubon Photography Awards

Climate-Threatened Birds

What Birds Tell Us About Climate Change's Threats

Just in time for COP21, a new international report shows how a warming world harms birds—and what needs to be done to save them.

Climate change threatens more than one-fifth of the world’s birds, according to a new report published in collaboration today by BirdLife International and Audubon. Titled The Messengers, the report draws on 92 studies and reviews—including Audubon’s own Birds and Climate Change Report—to show how birds from all seven continents will be affected by global warming.

It’s tough to say exactly how many birds will suffer from climate-induced disturbances in habitat, food availability, weather, predation, and disease. Out of 570 species considered in one recent international review (cited in the report, but not yet peer-reviewed), 24 percent are responding negatively to global warming. And while 13 percent of species seem to be reacting positively and 14 percent of species appear unaffected, it’s still unclear how 49 percent of species will respond to the impending global changes, the review found. “What’s striking is the global nature of this problem,” Stuart Butchart, head of science at BirdLife International, says. “There’s a consistent message that climate change is causing trouble for species in [many] places.”

Birds, it seems, are the mediums of this message; they’re highly reactive to changes in their environment, and are well studied as a result. With the Conference of the Parties (COP 21) convening in Paris next week, this “increasing body of evidence” of how global warming influences species survival becomes all the more relevant, Butchart says. “We want to draw attention to the importance of people mitigating climate change and reducing these risks.”

Here are the five biggest obstacles birds face in a warming world, according to the report.

Hostile Habitat

As the world heats up, birds are seeking out cooler temperatures by moving up—in both latitude and altitude. More than half of the birds in North America could be forced out of their ideal habitat by 2080, the Audubon Birds and Climate Change Report predicts. For example, the Common Loon (see below) may be pushed north of Minnesota in search of more suitable temperatures as the world heats up over the next several decades. All these range shifts will mean these species will have to find new sources of food and shelter, which may not be available where they end up.

Meanwhile, many species, including those in low-lying islands, African grasslands, Mexican valleys, and South Asian forests, are already seeing their ranges contract as the temperature warms, and some species are being forced uphill (though they may eventually run out of mountain to climb). 

One of the reviews cited in the report also reveals that at least 171 bird species are responding positively to the heat. These birds, including the Cetti's Warbler and the Rough-legged Buzzard, thrive in warmer temperatures.

Waves of Famine

Seasons are the equivalent of a biological alarm clock for birds: During migration, they time their flights to when they know plenty of food will be available at their destination—and the same is true of when and where they nest. But as global warming causes the seasons to advance, birds’ timetables are thrown off, sometimes with catastrophic results. In the Arctic, for instance, rising temperatures are causing insects in the permafrost to hatch earlier in the year, so they’re not around to be a food source for newborn shorebirds such as Baird’s Sandpipers. The birds are trying to adjust by breeding faster, too, but their chicks are still missing the peak harvest. 

Extreme Weather

Heat waves, droughts, fires, and super storms can result in “mass mortality wrecks,” especially when aggravated by climate change. As scorching temperatures become the norm in North America, small birds have to speed up their metabolisms to keep their bodies cool—but at some point they run out of energy, and their chance of survival plummets. Severe rainfall and offshore winds can also cause mass-mortality events for coastal birds: Models show the European Shag is particularly at risk.

Aggressive Predators

In some places, climate change is causing the hunters to become the hunted. Insectivores like the Collared Flycatcher and the Great Tit are facing more attacks from growing rodent populations in the Czech Republic. The higher temperatures favor the predators, which feed on eggs, allowing them to expand their ranks and loot more songbird nests. James Pearce-Higgins, the director of science at the British Trust for Ornithology, says that these types of changes in predator-and-prey interactions can further complicate where a species can survive. 

Exotic Viruses

Global warming is pushing diseases into former contagion-free zones. In the Hakalau National Wildlife Refuge in Hawaii, climate change is making the conditions farther up the mountains more suitable for malaria-carrying mosquitos, which are happily moving uphill and spreading the disease to new locations—and new birds. On a global scale, Butchart adds that environmental stressors could be making birds more susceptible to disease, but that connection is still not very clear.

The Upshot

The Messengers doesn't just predict these dire outcomes—the second half is dedicated to defining solutions that will work for people and wildlife. The core idea is that by making habitats healthier, they’ll be more resilient and better able to support wildlife. Additionally, the report points out that the obvious way to slow global warming and avert worst-case scenarios is to keep carbon in the ground.

Simply put, old-school conservation may be the best prescription. Preserving natural barriers such as wetlands and reefs, enabling sustainable farming and forestry practices, monitoring wildlife populations through citizen science—these actions help preserve the environment, and are also feasible in developing countries that are facing threats but don’t have abundant infrastructure or technology. The report emphasizes conserving important bird and biodiversity areas, and also getting new places protective status. These spots are vital for birds—for shelter, for food, and for raising their chicks—but they’re also valuable for people. “The reason birds thrive in these places is because of the wealth of biological activity and vibrant ecology,” Audubon’s Chief Scientist Gary Langham says. “They give all of us healthy fisheries, clean water and air, and so many other things we need for a high quality of life.”

The birds are speaking—let’s hope the world leaders heading to Paris next week listen to their message. And for those who won't be making it to Paris, here are some other ways to take action.