blue canary n. an emergency worker (especially a police officer or first responder) whose death alerts other personnel to a hazardous situation. Etymological Note: From the use of canaries in coal mines, whose death would alert miners to the presence of dangerous gases. (source: Double-Tongued Dictionary)
Further reading
If you speak a second or third language, you may remember the first time you dreamed in that new tongue. But does this milestone mean you’re actually fluent? And a couple’s dispute over the word regret: Say you wish you’d been able...
Understanding the varieties of conversational styles can mean the difference between feeling you’re understood and being insulted. “High-involvement” speakers interrupt or talk along with someone else to signal their enthusiasm...
While the word “respondent” does in fact, according to merriam-webster.com mean “one who responds,” I believe it is more common among those in the heroic professions to refer to themselvese as first responders as opposed to first respondents. Though I’m certainly no authority on the subject, I most often hear the word “respondent” in connection with civil proceedings at law or surveys.
I think you’re right. I’ll change the definition accordingly.