I always look forward to autumn with its crisp, cool days, brilliant foliage, and absence of bugs. But these changes bring about something I don’t especially look forward to, although I am always fascinated with it – the migration of birds to points south.

On a hike up Schoodic Mountain, I saw a migrating cooper’s hawk, two merlins – one zoomed over the ridge we were sitting on – and three hawks circling together I thought could have been broad-winged hawks. The trail up to the peak produced a blackpoll warbler in fall plumage, and I prided myself on making the identification. Most adults outside of the breeding season look maddeningly similar to one another, but the diagnostic clue to the blackpoll is its flesh-colored, rather than dark, legs. This differentiates it from other warblers with similar body markings.

At the bottom of the trail I picked up black-throated green and black-throated blue warblers, and I viewed them as old friends. Both of them have distinctive plumages and blessedly easy songs to identify them by. The former is one of the most often heard songbirds during spring and early summer. I’d hear both versions of its song on every hike I went on, no matter where I was. Sometimes, it was “zee-zee-zee-zoo-zee.” The alternate was a song sounding phonetically like “trees, trees, murmuring trees.”

The latter is a bird I learned to identify just this spring, and I most often heard it on trips to Baxter State Park. Its fervent, ascending “beer, beer, beer, BEE!!” always brought a smile to my lips.

On this, day, however, the birds were silent, only emitting short call notes at intervals. They were foraging intently, building up energy reserves for their grueling, hazardous flights to South America.

One species of songbird includes the United States as its wintering range. The yellow-rumped warbler – so named for the conspicuous patch at the base of its tail – is one of the most common warblers in North America. It is an ecological generalist, which means that it does not depend entirely upon a particular habitat, food, or foraging behavior to survive.

The yellow-rumped switches from a summer diet of insects to a winter diet of fruit. Researchers have found it can digest the waxes in bayberries, which enables the birds to winter in coastal areas as far north as Nova Scotia.

I came across a flock of fledgling and adult yellow-rumpeds as I rode home along the University of Maine bike trail. It was their call notes that first drew my attention to them as they foraged among the trees.

The young still had the barest trace of natal down clinging to them, and I watched with amusement as one tried to manage a berry it had just picked. The fruit was too big to be swallowed whole, and after several tries the bird ended up dropping it. Undeterred, the youngster selected another berry and this time found a stout branch to lean it against while it snipped small mouthfuls.

I smiled, glad that at least one species of warbler would be around for a while longer.

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