They preach all day.

Preach, preach, preach, rain or shine, morning, noon, right into the evening. Often, theirs is the only voice you can hear. “Over here, see me? Here I am. Look at me. See me?”

Fortunately, it’s a pleasant voice, and you don’t need to be sitting in a hard, wooden pew to listen to it. You can be at a ball field surrounded by forests, or at a local park, or on a hike at a land trust preserve, or even taking the garbage to the curb at your own home.

No, it’s not a disciple from a new (or old) religious order we’re talking about. It's the red-eyed vireo, or as we and other bird enthusiasts call them, a preacher bird. (Let the record show that we have two former preachers in the family, lest anyone think we have anything but respect for the field!)

The red-eyed vireo may be the most common bird most people have never heard of. We recently kept track of every place we heard a red-eyed vireo singing: the supermarket, the ballfield, the park, the hardware store, the diner, the office, the clinic, the pharmacy, the library, the land trust headquarters, and of course the few in our neighborhood.

Interestingly enough, we didn’t see a single one of these. That’s partly because we didn’t try; but, even when you do, this can be a difficult bird to get a good view of during the summer breeding season.

They love to stay in the branches of a thickly leafed broad-leaf tree like a maple or oak, and their plumage is far from flashy. A small bird with a dull olive back and wings, their white underparts and white eyebrow, bordered along the top by a thin strip of black eyeliner, seem flashy by comparison.

Even their steel gray cap is nothing to write home about. Add to it their often rather sluggish movements and the red-eyed vireo easily fades into the shadows of the forest canopy.

But not so their song! Among song typology, the red-eyed vireo’s is often described as one of the “sing-songers.” The best known of bird songs in this category is that of the American robin, but all tend to sing a series of short, rich, whistled, rather melodic phrases that usually alternate high then low.

Compared to the American robin song, the red-eyed vireo’s is slower, more measured and more repetitive. Unlike the robin, the preacher bird tends to sing almost continuously starting before sunup, continuing through the afternoon heat, when every other bird seems to be napping, and into the evening.

A close view of a red-eyed vireo reveals its most striking feature: its red-eye. Close up, you’ll also see its finely hooked bill, which hints at their apparent relatedness to the shrikes (a family of songbirds that act more like small hawks, some species catching and killing small mammals and birds).

Vireos are not that fierce, instead feeding on insects and, during fall migration, adding berries to their diet. They build a small nest suspended from a fork in a tree where they lay their 3-4 eggs.

So the next time you step outside, or open a window in your home or office, take a listen for the preacher bird.

Perhaps there is one singing right now, within ear shot, as you are reading this column.

Dr. Jeff Wells is the senior scientist for the Boreal Songbird Initiative. During his time at the famed Cornell Lab of Ornithology and as the Audubon Society's national bird conservation director, Dr. Wells earned a reputation as one of the nation's leading bird experts and conservation biologists. Jeff's grandfather, the late John Chase, was a columnist for the Boothbay Register for many years. Allison Childs Wells, also formerly of the Cornell Lab of Ornithology, is a widely published natural history writer and a senior director at the Natural Resources Council of Maine. Together, they have been writing and teaching people about birds for decades. The Maine natives are authors of the highly acclaimed book, “Maine's Favorite Birds.”