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We've all heard the canary-in-the-coal-mine history.

Just over 100 years ago, in 1911, John Scott Haldane, a Scottish physician and research professor of physiology at Oxford University became known to some as "the father of oxygen therapy," in part because he used science to test and recommend using birds — specifically canaries — to detect carbon monoxide and protect coal miners.

Canaries, and other birds, are good early detectors of carbon monoxide because they need immense quantities of oxygen to enable them to fly. Their anatomy allows them to get oxygen when they inhale and still more when they exhale, by holding air in extra sacs. That meant that in mines they got a double dose of air, along with any poisons the air might contain. If they became ill or died, the miners had an early warning to evacuate.

It wasn't until 1986, when more scientists developed the "electronic nose," a detector with a digital reading, that the canaries were freed from their dangerous duty, according to Smithsonian Magazine.

But birds — some 389 North American species of them to be exact — are still warning us of danger from carbon monoxide and its cousin carbon dioxide — two important drivers of climate change. And scientists again are researching the birds' warnings and telling us how to read the signs.

Scientists and the Audubon Society, in a new report titled Survival by Degrees, warn that if we don't take action now to cut carbon emissions, we'll see the die-off of two-thirds of this continent's 604 species as temperatures warm and destroy bird habitats and disrupt their feeding patterns.

Audubon scientists used 140 million bird records — including observational data from bird lovers and watchers across the country. The scientists plugged the bird data into the same climate models used by more than 800 experts in 80 countries to map where each bird might live in the future under a changing climate.

In our tri-state region, Audubon researchers found that heat, heavy rain and urbanization are the primary threats.

Kevin Calhoon, assistant curator of forests at the Tennessee Aquarium and an avid birder, regularly sends local bird-watching reports to North American Birds Magazine. In his Aug. 1-Nov. 30, 2016, report, he wrote: "The whole season broke records for warmth and drought." He noted normal temperature departures of 3.7, 6.1, 6.1 and 4.5 degrees warmer than average in August, September, October and November, respectively.

The following spring, in his March 1 — to June 1 report in 2017, Calhoon wrote:

"Hamilton County Migration Count had 123 species, well below average."

This time Calhoon noted the average rainfall was above average. And, again, so were the temperatures: 2.6 F in March, 6 F in April and 1.6 F in May.

Audubon's "Survival by Degrees" indicates that spring heat waves especially endanger young birds in the nest.

But Calhoon says that because birds are notorious travelers, it isn't just our habitat and weather that makes a difference.

"It's getting harder and harder to predict when some birds will migrate through [our region]."

Scientists fear extinctions because the heat in many cases is pushing birds into zones that are not right for them, where or when there is less food or more urbanization.

"It's very complicated," Calhoon says. "The northern water thrush, for instance — normally we'd see it come through later, but now it's here in the third week of April. And we see birds staying here longer. The Philadelphia vireo was here into November last year. That's very unusual."

The good news is that science — while showing us which birds are most vulnerable — also shows that if we take action now we can help improve the chances for 76% of species at risk.

Our planet has been warming rapidly since the Industrial Revolution. We've already reached a 1.8 F rise, and we see the impacts with stronger hurricanes in the East and severe drought and wildfires in the West.

In mapping the possible bird extinctions, the Audubon researchers factored in the three future warming scenarios that thousands of climate scientists around the world use: 2.7 F, 3.6 F and 5.4 F.

Our goal should be to hold warming at the 2.7 F range, otherwise we will face increasingly dire consequences. If we do nothing to reduce the amount of carbon released into the atmosphere, that next warming tier — 2.7 F — is imminent. The second rise would happen as soon as 2050 and we'd reach the 5.4 F range by the end of the century.

The birds are telling us — warning us.

In Hamilton County at just that first tier, we have four high vulnerability species, including the brown-headed nuthatch. If we warm to the second rise, the number of high vulnerability species increases to seven and includes the red-headed woodpecker and Eastern towhee. At the third level of warming, 14 species are highly vulnerable, including the Eastern whippoorwill and scarlet tanager.

Not to mention what the birds' warnings mean for us.

"The bottom line is that by 2050 we must break even in carbon emissions by reducing the amount of carbon we produce and by absorbing what is produced through natural solutions like reforestation or with technology that removes carbon from the air," according to the Audubon report.

Urge Congress to act now. And do what you can reduce your carbon footprint.

Read the report here.

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