A bird rescue and rehabilitation center recently put out a query on the Maine birding listserve website. They asked if anyone was aware of any chimney swift roosts that were still active, as they had some young chimney swifts that they had rescued and raised that needed to be released with some of their brethren.

he sound of chimney swifts is omnipresent all summer where we live — so omnipresent, in fact, that it can easily fade into the background soundscape and eventually not be noticed.

When the chimney swift question was posed on the listserve, we realized that we couldn’t remember hearing any chimney swifts lately; we were hard-pressed to remember when that last day of chattering swift noise had graced our ears.

So it is that many of the birds we look forward to seeing and hearing each spring go unnoticed when they leave each fall. Eastern kingbirds are another of the birds that we get used to hearing in the summer as they aggressively go after crows, hawks and eagles. They too head south for the winter but the last day that we hear one is always hard to remember.

For some people it’s their backyard ruby-throated hummingbirds that one day slip away for the season while they are busy with fall chores, back-to-school prep, or work. Yes, there’s a tinge of melancholy when we finally notice that they are no longer here.

Hopefully that melancholy is tempered by the realization that “our” birds are now blessing the backyards of bird lovers all along their southward migration path. We, on the other hand, are also being showered with the millions of birds migrating south from points north, especially from the boreal forest region of our neighbors in Canada.

As our migrants leave for the winter, it’s important to note that Sept. 1 marked 100 years since one of our once most abundant birds — the passenger pigeon — officially became extinct, having forever left our backyards long before. The last passenger pigeon, nicknamed Martha, died in the Cincinnati Zoo on Sept. 1, 1914. She was the last of a species that once numbered in the hundreds of millions and occurred right here in Maine.

Hopefully, we will all think about this heartbreaking loss and ensure that history doesn’t repeat itself on our watch by paying close attention to the natural world around us and by supporting conservation efforts locally and nationally.

Jeffrey V. Wells, Ph.D., is a Fellow of the Cornell Lab of Ornithology. Dr. Wells is one of the nation's leading bird experts and conservation biologists. His grandfather, the late John Chase, was a columnist for the Boothbay Register for many years. Allison Childs Wells is a senior director at the Natural Resources Council of Maine. Both are widely published natural history writers and are the authors of the book, “Maine’s Favorite Birds.”