The Crossville City Council tonight voted unanimously to designate the Eastern Bluebird as the official bird for the City of Crossville. Eastern bluebirds are highly social birds. At times, they gather in flocks of a hundred or more. However, they are territorial during the breeding season and may continue to defend a feeding area throughout the winter. Mating occurs in the spring and summer. A mature female typically raises two broods each season. Nests are constructed in trees within abandoned woodpecker holes or other cavities that provide adequate protection (usually several feet above ground). Construction of the nest is done primarily by the female and takes around 10 days to complete. These nests are small, cup-like structures lined with grass, feathers, stems and hairs. Each female lays three to seven light-blue or, rarely, white eggs. The female incubates the eggs, which hatch after 13 to 16 days. The young cannot care for themselves upon hatching. The female broods the chicks for up to seven days after hatching. Fledglings leave the nest 15 to 20 days after hatching. Eastern bluebirds can live for six to 10 years. The record lifespan for a bluebird was 10 years and five months. However, a majority of bluebirds die within their first year of life. Starvation and freezing can threaten young bluebirds, but most threats come from other animals. A group in Cumberland County has constructed bluebird boxes and placed them in various areas in the county as well as the city to give the bluebirds a place to nest.