The Common Loon nested in Massachusetts historically, but was extirpated in the late nineteenth century. In 1975, however, a pair of loons was discovered nesting in Quabbin Reservoir. The population has increased since then, and today approximately 32 territorial pairs can be found on 14 lakes, ponds, and reservoirs in the Commonwealth. Common Loons reach the southern limits of their North American breeding range in Massachusetts. Large piscivorous birds that rely on sight to capture their prey, loons require relatively large nesting territories and water of high clarity; hence their population growth here is limited by the availability of this habitat. The Quabbin and Wachusett reservoirs support the core of the state’s total loon population, with 16 and 4 pairs, respectively.