Spring means many things to people, but to me the essence of the season is bird song.

Each day introduces more voices to the avian chorus, and it is a joy to pick them out from the rest. This is especially so with the small wood warblers, which are most often heard but not seen. Identifying who they are by voice alone may be a daunting task for the beginning birder, but one little songster makes it easy: the black-throated green warbler.

This warbler is one of my favorites. It is especially easy to identify by sound, for it has two distinctive, easily remembered songs.

One song has an accented ending and sounds like “zee-zee-zee, zoo-zee.” The male uses this song to establish a bond with his mate. He may sing this anywhere, even while he is foraging.

Before he finds a mate, he will sing this song most often during the day. After he finds a mate, he will sing this version during late morning and afternoon hours.

The second song has an unaccented ending and sounds like “zoo, zee, zoo-zoo zee.” This can be represented phonetically as, “Trees, trees, murm’ring trees.” The male sings this to advertise his territory or in response to another male. He will select a high, prominent perch for this, and will mostly sing it during dawn and dusk until he finds a mate. After he finds a mate, he sings this version mostly during the early morning hours.

In addition to having a memorable voice, this warbler repeats its songs many times. There is on record one male who sang 466 songs in one hour. This, coupled with the fact that it is one of the most common warblers inhabiting coniferous forests of the northeast, makes it impossible not to learn to identify by voice alone.

However, if you are lucky enough (and quick enough) to actually catch sight of it, the black-throated green warbler is easy to identify by sight. Just remember: yellow face, black throat, neck and chest, and olive-green back and wings. The wings also have two prominent white bars. The female is almost identical, except the black does not extend down her chest and is confined to her neck. Her throat, just below her beak, is yellow.

Black-throated greens winter in southern Texas down through Mexico and Central America, South Florida, and the West Indies. Males are first to reach their breeding range, which includes northeastern North America and southwestern Canada, followed by females. They may produce one clutch of three to five eggs each season.

This warbler has kept me company with its song wherever I’ve gone. No matter that the song’s function is to serve as a warning to others of its kind. To me it sounds cheerful and uplifting, an eternal sign of spring.

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