Singing by birds is most often associated with springtime territorial behavior, but there are lots of local species that will sing throughout the year. This tendency has been enhanced by recent abnormally warm temperatures, but some of our birds sing during winter even at below-normal temperatures. This is more a result of the increasing daily photoperiod, or exposure to daylight, than actual temperatures. Many are species that will remain with us through the year.
Northern cardinals normally begin singing around the first of the year. I heard the first one just a few days after Christmas.
Male Carolina wrens will sing their rollicking song every day of the year. Bonded pairs stay together all year. All the males in an area keep up the singing to keep the territory lines intact. Pine warblers give their musical trill from the tops of pines on calm winter days. If you are in uptown Charlotte on sunny days, listen for the complex song of the song sparrow coming from shrubbery. American robins sing in winter, especially when they are in flocks, but it usually is a soft murmur of their typical song. The warm spell we had recently had some of them really opening up, though.
Some singers call the southern Piedmont home only in the winter, however. White-throated sparrows sing their “Old Sam Peabody” song from woodland thickets. Overgrown fields with scattered pine saplings might attract fox sparrows with their loud, melodious sounds. On some warm days, hermit thrushes might be heard giving their flute-like songs from deep in the woods. A winter wren might even burst out its incredibly loud, long, and complex carol. When any of these nonbreeders sing, I suspect it is to keep touch with other members of their species.
And then some birds are already nesting and appropriately vocalizing. You might not call the deep, booming hoots of the great horned owl a song, but it serves the same purpose. Nesting is well under way for them already, and both sexes advertise their presence. I have heard them at numerous locations in the area at dusk. Also at dusk, the nasal call of the American woodcock heralds the start of their courting season, well under way by now as well.