The Northern flying squirrel (Glaucomys sabrinus) is one of two species of the genus Glaucomys, the only flying squirrels found in North America (the other is the somewhat smaller southern flying squirrel, G. volans). They are found in coniferous and mixed coniferous forests across much of Canada, from Alaska to Nova Scotia, and south to the mountains of North Carolina and west to California in the United States. They are light brown with pale underparts and grow to a length of 25 to 37 cm (10 to 15 in). They are good gliders but clumsy walkers on the ground. They feed on a variety of plant material as well as tree sap, fungi, insects, carrion, bird eggs and nestlings. They mostly breed once a year in a cavity lined with lichen or other soft material. Except when they have young, they change nests frequently, and in winter a number of individuals may huddle together in a shared nest. Unlike most members of their family, flying squirrels are strictly nocturnal.