They are "canaries in a coal mine" for the health of such habitats.

That's where the phrase "Canary in a coal mine" came from.

These youngsters have become the unfortunate local version of canaries in a coal mine.

In other words use a "canary in a coal mine" approach.

To me the Columbine shootings was like the canary in a coal mine."

Like canaries in a coal mine, he writes, "they are an index of the health of a place."

The idea is to make fish that glow when they encounter certain pollutants, the marine equivalent of a canary in a coal mine.

"Many people believe that birds are the barometers of the health of the environment - canaries in a coal mine."

Dr. Woodward likened emergency departments to canaries in a coal mine.

If the silence lasts too long, the train starts to function like a canary in a coal mine, speaking volumes with its absence.

Canaries were formerly used by miners to warn of dangerous gases ("canary in a coal mine").

"Canary in a coal mine," Bates suggested.

But he feels a bit like a canary in a coal mine, especially when he sees many newspapers shying away from being controversial.

Ms. Haddock said that dogs could serve as an early-warning system - the urban equivalent of canaries in a coal mine.

And because loons return to the same territory year after year, they can serve as barometers of pollution, like canaries in a coal mine.

The phrase "canary in a coal mine" is frequently used to refer to a person or thing which serves as an early warning of a coming crisis.

Shorting may act as a "canary in a coal mine" to stop unsustainable practices earlier and thus reduce damages and forming market bubbles.

"When they told me where my office was," Mr. Holden said, peering out of a corner window, "I felt like a canary in a coal mine."

This goes back to the idea of "canary in a coal mine", where the B cells act as the canary to sniff out danger ahead of time.

She is the colony's "canary in a coal mine": If the Chinese stifle her, it will be a sure sign that Hong Kong is in trouble.

Thus, like a canary in a coal mine, researchers can examine stream hydropsychid populations to assess stream health (see EPT or Index of biological integrity).

Stack canaries, named for their analogy to a canary in a coal mine, are used to detect a stack buffer overflow before execution of malicious code can occur.

Markey also said that, at the time, 2010 was the hottest recorded year, and "scientists agree arctic ice is a canary in a coal mine that provides clear warnings on climate."

The spotted owl, which weighs two pounds in maturity, has been likened to a canary in a coal mine: Its health is an indication of the health of the entire ecological system.

On that optimistic note, while Sylvester Maxwell contemplated being compared to a canary in a coal mine, Mr. Stevens said, "When we disembark, please stay with me at all times."