Every learning experience or goal I’ve striven for has had its own particular ebbs and flows. The first burst of high energy and productivity undoubtedly was followed by a plateau, where it seemed as if I was stuck in a rut.

Then, unexpectedly, something would happen and I’d find myself at the next level – and yet another new world was opened up to me.

I’ve found this to be true as I’ve worked to improve my skills at bird identification. There have been many milestones; one of them has been the ability to identify the blackpoll warbler.

This warbler belongs to a group of birds known as wood warblers, which are small and mainly insectivorous, foraging among tree canopies and dense foliage. In fact, they are most often heard, but not seen, because of this trait.

The blackpoll is more visible because of its habit of perching atop spruce or fir trees as it sings. Its song seems at first to be a flat trill. But once I became attuned to picking up slight variations in tone and cadence, I realized that it actually starts out low, rises to a noticeably louder pitch, then fades gently away. Many of my memories of Baxter State Park trips are of this stalwart bird sitting conspicuously atop a pine tree, singing its little heart out.

The breeding range of these birds extends from northwestern Alaska across Canada, and into northern New England. They migrate in autumn to the western Amazon basin in Brazil. Sometimes they may overshoot and end up as far south as Chile and Argentina – earning them the longest migration route of any North American warbler.

This journey is epic in its dimensions. Birds departing Alaska travel east across the continent; many then take off from the Atlantic Coast somewhere north of Cape Hatteras and begin a nonstop flight over water to South America.

How can a bird that weighs less than half an ounce store enough energy for such a grueling flight? Researchers studying the dynamics of these migrating warblers have been quoted as saying, “If a blackpoll warbler were burning gasoline instead of its reserves of body fat, it could boast of getting 720,000 miles to the gallon.”

Now that’s what I’d call fuel-efficient.

Chris Corio, a volunteer at Fields Pond Nature Center, can be reached at fieldspond@juno.com.