The Fore River is a short horn-shaped estuary, approximately 4 mi (6.4 km) long, separating Portland and South Portland in Maine in the United States. Many of the port facilities of the Portland harbor are along the estuary, which is formed just southwest of Portland by the confluence of several creeks. The Stroudwater River also flows into the river. It enters Casco Bay on the southeast edge of Portland. Like other coastal areas along the Gulf of Maine, it experiences moderately high tides and thus the water level in the estuary and the harbor varies greatly throughout the day, leaving mud flats at low tide. It is spanned by three bridges: the Casco Bay Bridge which connects Portland to South Portland, Veterans Bridge which carries Route 1, and a causeway which carries I-295. The lowland area, where salt and freshwater marsh meet, often provides great bird-watching opportunities. Red oak and white pine contribute to a habitat for many songbirds and small mammals in the upland area.