Common Tern

Common Terns are one of New Hampshire’s bird conservation success stories. The species was hunted extensively for its plumes in the nineteenth century, leading to its near extirpation from the New England coast. Following protection, it recovered and was known to nest on several New Hampshire islands, including Lunging Island (in the Isles of Shoals) and others in Great Bay and off New Castle. By the 1950s however, increasing gull populations had displaced terns from the Isles of Shoals, while human disturbance likely kept numbers low in other areas. During this time, more and more Common Terns opted to nest in the salt marshes around Hampton-Seabrook Harbor, despite this habitat being at risk from flooding and predation. By the early 1990s the statewide population was probably only a couple dozen pairs.

The second wave of conservation started in 1997, when NH Audubon and NH Fish and Game initiated an attempt to restore terns to White and Seavey Islands at the Isles of Shoals. This involved active (non-lethal) attempts to discourage gulls and use of recordings and decoys to attract terns, and exceeded expectations when six pairs nested that first year. The colony grew rapidly and now averages over 3000 pairs, making it the largest Common Tern colony in the Gulf of Maine. Although this project has been wildly successful, the terns that now nest here continue to face additional threats, including changes to food supply (see below), sea level rise, and the ongoing risk of gull predation. Without a human presence on the islands during the breeding season, it’s likely that gulls from nearby colonies on other islands would decrease the likelihood of terns continuing in current numbers.

Terns feed primarily on small fish and crustaceans that are captured by diving. In New Hampshire important fish species include sand lance and Atlantic herring. They can range widely in search of prey, and shift foraging locations based on prey availability, but generally don’t fly more than 15 miles from their colony. Sometimes you can find congregations of feeding terns at the mouths of harbors and rivers at the changing tides, which might sometimes bring food closer to the surface. Adults bring food back to chicks whole, and herein lies one of the threats to terns in the Gulf of Maine. As the water warms, southern species like the butterfish are becoming more common. While an adult tern can swallow a butterfish, they are two wide for small chicks, which fail to get sufficient food if butterfish comprise too large a portion of the food their parents capture. The long-term implications for this treat are being actively studied at the Isles of Shoals.