Shifting flight patterns
Climate change’s impact on birds

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peacock

The peacock. Science suggests that climate change is impacting the bird’s breeding and migration patterns. -Photo: National Audubon Society

Could it be that some day the “oh-sweet-canada” whistle of the white-throated sparrow or the steady musical trill of the pine warbler won’t be heard in Wisconsin?

At least two climate change models — one from the Canadian Climate Center and another from the United Kingdom’s Hadley Center for Climate Prediction and Research — indicate that by 2100 many bird species now found in Wisconsin will be locally extinct, including the white-throated sparrow, red-breasted nuthatch, mourning warbler and pine warbler.

Other research efforts show that climate change is impacting birds and their behavior — especially migration and breeding —around the globe, raising questions for the fate of the proud peacocks of Pakistan, the brown pelicans of California, the pine warblers of Wisconsin and more.

“The science is clear: Carbon pollution is profoundly damaging to our air, water, natural spaces and wildlife, and failure to tackle the problem is no longer an option,” said David Yarnold, president and CEO of the National Audubon Society. 

Researchers have looked at the impact of climate change on specific species, such as the peacock, a bird indigenous to Pakistan that typically breeds in June and July and nests through the summer. Delays in the monsoon season have brought heavy rains in September that can damage peacock eggs. And severe flooding has caused some peacock populations to migrate to more mountainous habitats.

At the University of East Anglia in England, scientists in the school of biological sciences studied a population of Icelandic black-tailed godwits for two decades. During that time, the flock advanced the end of its spring migration by two weeks.

The scientists found that a younger generation was pushing up the schedule. “We found that birds hatched in the late 1990s arrived in May, but those hatched in more recent years are tending to arrive in April,” said lead researcher Jenny Gill. “So the arrival dates are advancing because the new youngsters are migrating earlier. 

“Climate change is likely to be driving this change because godwits nest earlier in warmer years and birds that hatch earlier will have more time to gain the body condition needed for migration and to find good places to spend the winter, which can help them to return early to Iceland when they come back to breed.”

One of the most significant studies on the subject, “Birds and Climate Change — Ecological Disruption in Motion” from the Audubon Society, examined 40 years of data collected by citizen scientists in the organization’s annual Christmas Bird Count.

Each year, the citizen scientists, most of them avid birdwatchers, go out on a specific date in December or January and count birds, noting the species and their number. The data are collected and used by Audubon scientists to identify patterns and trends over time.

An analysis of the counts provided evidence that climate change is seriously impacting natural systems, especially influencing migration. The co-author of the Audubon study, Greg Butcher, wrote, “Birds are showing us how the heavy hand of humanity is tipping the balance of nature and causing ecological disruption in ways we are just beginning to predict and comprehend.”

The Audubon research was focused on North America and showed a strong correlation between shifting ranges and winter temperature trends. Birds are found further north in warmer winters than they are in colder winters. Also, many birds are moving away from coastal areas, where oceans help moderate temperatures, and are being seen farther inland as temperatures rise.

The birds, according to Audubon, are following the biological imperative to move into areas with suitable climate. Over the 40-year period, the red-breasted merganser has moved 317 miles north and the green-winged teal, 157 miles north. The pine siskin has moved 288 miles north and the spruce grouse, 316 miles north.

The data also showed that:

• Twice as many bird species moved north as south.

• Twice as many species moved inland as moved coastally.

• There is a high correlation between the rate of winter population change for species in states and the winter temperature in those states.

While some species appear to be adapting — moving north, shifting inland — other species are at risk. Grassland birds, for example. Their habitats have been so decimated by human overuse that there are few places to go to find a more suitable habitat.

Audubon also has concerns for the fate of ice-loving birds, such as the Ivory and Ross’s gulls, Arctic-breeding shorebirds such as the American golden-plover and coastal birds such as the piping plover.

“Common sense dictates that we act now to curb the causes and impacts of global warming to the extent we can, and shape our policies to better cope with the disruptions we cannot avoid,” according to Butcher.

Earlier this month, the Obama administration announced plans to reduce carbon dioxide emissions from U.S. power plants, many of which are coal-fired, by 30 percent from 2005 levels by 2030.

The announcement was well received in environmental circles.

Audubon’s Yarnold said, “Cutting carbon pollution is the single most important thing we can do to protect birds — and ourselves — in a changing world. Sure, energy companies are going to howl, but they can’t get a free pass to dump harmful waste into our air any longer, and they’re fully capable of innovating their way to solutions.”

Birdwatchers who participate in the Christmas count also welcomed the announcement, but said more must be done by everyone.

“I’d like everyone who reads this to go outside. Take a look around. Listen,” said bird enthusiast Ginny Manzerik of Milwaukee. “There’s a good chance that the wildlife that you see and hear will be birds. Listen to that warbler and then think about what you can do to minimize your impact.”

Additional research shows:

• Lowland and foothill bird species in Costa Rica have extended their ranges up mountain slopes.

• Breeding birds in the United Kingdom extended their ranges north by 12 miles in association with warming temperatures.

• Warming ocean temperatures contributed to a 90-percent decline in the population of sooty shearwaters on the west coast of the United States.