Potential Impact of the Massachusetts Maritime Academy Wind Turbine on Common (Sterna hirundo) and Roseate (S. dougallii) Terns

Massachusetts Maritime Academy (MMA) conducted a study to evaluate the potential impact of the MMA wind turbine (Vestas V47-660 kW) on birds, including common terns (Sterna hirundo), which are protected at the state level, and roseate (S. dougalii) terns, which are protected at the federal level. We found that common terns were relatively abundant on the water adjacent to the wind turbine, especially during the post-breeding period (7 Aug-30 Sep). Roseate terns, however, were much less abundant than common terns, and their presence at the study site was nearly limited to the chick-rearing period (19 Jun-6 Aug). Both species were least abundant during the nesting period (24 Apr-18 Jun). During the study, we observed 253 terns passing through wind turbine airspace (i.e., within 50 m of the wind turbine). Most (n = 226) were common terns, 1 was a roseate tern, and 16 were unidentified to the species level. Terns (all categories) were most abundant in wind airspace during the chick-rearing period, especially during morning hours (0530-1100). However, their abundance was dependent upon the operational status of the wind turbine rotor. Terns were less abundant in wind turbine airspace when the rotor velocity was >1 rpm than when the rotor velocity was <1 rpm. The few terns that did enter wind turbine airspace when the rotor was operating usually avoided altitudes equal to the rotor-swept region. We found one bird carcass (a laughing gull, Larus atricilla) suspected of colliding with the wind turbine rotor. After correcting for scavenging activity and searcher efficiency, we estimated that the wind turbine probably contributes to 2.15 avian fatalities per year. This rate is approximately average relative to wind turbines elsewhere.