photograph and text by Brian Willson

What does a Black-Throated Green Warbler sound like?
Zee, zee, ZOO, zee!

Assuming you can endure the deerfly swarms long enough to stand for a moment in the woods these days, you might well hear—amid the voices of the red-eyed vireo and the hermit thrush and the occasional eastern wood-pewee—the summer song of a black-throated green warbler.

Black-throated greens are one of our more exotic-looking local birds, but they’re small and skittish enough to escape notice most of the time. It’s easier to hear them first then go looking for ‘em. But it can get tricky even knowing what to listen for: like a number of local species—don’t ask me why—their song goes through a transformation as the year moves on, as nesting progresses, as spring turns into summer.

In any season, the “BTG” is one of a few of our resident warblers with peculiarly buzzy-sounding voices. (Others include the northern parula and the black-throated blue.) In spring, as the yellow-cheeked males began vying for nesting sites, their urgent-seeming song might be written: Zee-zee-zee-zee-zee-zooo-ZEE!

Like the spring song, the bird’s typical summer call has both clear and buzzy notes but seems slower and more languorous, befitting of the season: Zee, zee, ZOO, zee.

Curiously the “ZOO” part of this song is the solitary clear note of the four—a note that, in fact carries a lot farther. Often I first know this species is about by hearing a lone, distant ZOO! off in the trees.

So if you’re in or near a wooded glade some sunny afternoons, stop and listen for this little warbler’s signature summer song.