Many people are familiar with the haunting call of the Common Loon (Gavia immer) from trips to northern New England. These fascinating fowl were extirpated (absent from) from the Massachusetts landscape from the early 1900s until 1975, when a nesting pair on the Quabbin Reservoir successfully produced two chicks. Today, the DCR water supply reservoirs, Quabbin and Wachusett, are breeding habitat for the largest concentration of Common Loons in the Commonwealth.
These birds typically nest on large lakes and reservoirs with an abundance of fish and suitable nesting locations (usually small islands or peninsulas). When loons reproduce, the mating pair defends a territory associated with their nesting location, which can vary in size depending on the water body. They vocally, and sometimes physically, defend a territory from other loons. Survey data from 2009 identified 32 territorial pairs of loons in Massachusetts; 23 of these pairs – about 75 percent of the total – occurred on DCR Division of Water Supply Protection water bodies…primarily Wachusett and Quabbin Reservoirs.
Why does the Division of Water Supply Protection (DWSP) care about loons? DCR is a steward for these listed Species of Special Concern in Massachusetts. As an added benefit to DCR’s watershed management objectives, loons are also an excellent indicator of water quality: they are rarely found where the water is even remotely polluted or murky; they need clear, clean water since they rely on eyesight to catch fish; and they are very sensitive to pollutants. Thus the loons act as a “canary in the coal mine” – a significant dip in productivity or the complete absence of loons could signal a water quality problem. The loons’ presence on the reservoirs in such small numbers does not pose a water quality risk, unlike the problematic populations of geese and gulls the impacts of which DCR works to minimize and mitigate.
Wildlife biologists in the Natural Resources section of DWSP spend significant time and effort protecting loons and enhancing their habitat. An intensive research project has been ongoing since 1999 to provide detailed information about loons nesting on DCR water bodies and enhance DCR’s ability to effectively manage this species (for example, see this 2004 edition of the Division’s Downstream newsletter). The ongoing research involves constructing, repairing, and deploying artificial nesting structures (loon rafts) each spring. These rafts are important because the water level fluctuations of an active drinking reservoir can flood or strand a loon nest. Most unsuccessful nesting attempts on natural islands are due to fluctuating water levels. The rafts, however, move up and down with the corresponding water levels. Once the loons begin nesting (usually after Memorial Day), DCR wildlife biologists monitor them weekly to determine reproductive status and success. Efforts are made to capture and leg band adult and juvenile loons to facilitate remote monitoring of individual reproductive performance and lifespan. In addition, blood and feather samples are taken from captured loons to evaluate various contaminant levels, including mercury and PCBs. The research project has allowed the Division to track individual loons over time, document site fidelity and mortality, and closely monitor reproduction and chick survival.
Loons are especially susceptible to lead poisoning. In 2001, the Division Fisheries and Wildlife (MassWildlife) Board prohibited the use of all lead sinkers for the taking of fish in Quabbin and Wachusett Reservoirs. This prohibition was expanded in 2009 to the use of lead sinkers, lead weights, and lead fishing jigs with a mass of less than 1 ounce in all inland waters of Massachusetts. This regulatory change will take effect on January 1, 2012.
Information on lead sinkers and loons www.mass.gov/dfwele/dfw/recreation/fishing/lead_sinkers_loons.htm