What's with Least Terns?
Have you ever been walking along Duxbury Beach and suddenly had a small, white bird dive at you, calling shrilly, seemingly out of nowhere? While often overlooked by the public on Duxbury Beach due to the notoriety of their fellow nesters, the Least Terns are more likely to be seen by the public due to their tendency to fly over the beach and water and their loud call.
Least Terns are listed as a Species of Special Concern in Massachusetts and protected under the state Endangered Species Act (MESA). Unlike the Piping Plover, the Least Tern is not listed under the Federal Endangered Species Act, however, the Reservation is responsible for managing Least Terns according to the state guidelines. The regulations require certain distances of protection from nesting and chick nursery areas in pedestrian and OSV areas, just like the Piping Plover. These protected areas increase once chicks are hatched where terns are adjacent or within the OSV beach.
Least Terns are colonial nesters, meaning they nest in groups, ranging from <10 to hundreds of pairs. They nest in similar habitat to Piping Plovers and often overlap on Duxbury Beach. Like the plovers, Least Terns nest in scrapes in the sand or cobble, and lay eggs that are very well camouflaged. Least Terns arrive back in Massachusetts from the wintering grounds in May, a month and a half later than the plovers, which means nesting can extend later into the summer.
Least Tern chicks are semi-precocial, meaning they are able to leave the nest bowl after hatching but rely on the adults to bring food. Because of this, chicks are often hard to see and spend a lot of their time hiding in the vegetation, in the shade of drift wood, and in the wrack-line. However, chicks can move far distances down the beach due to disturbance or other causes, and like the plover chicks, are well camouflaged on the beach and tend to lay motionless if scared. This can make them very vulnerable to pedestrians and drivers who may be oblivious to their presence.
Like the restrictions due to the Piping Plovers, restrictions on the beach are different each year (and throughout the season) and vary in size and location as colonies shift nesting locations. Least Terns will move colony locations overnight when disturbed due to overwash, predators, human presence, etc. While a colony might be gone one morning, they can return just as suddenly and start over with fresh nest attempts.
Next time one of these feathered fighter pilots swoops down on you, please give them some space so they can get back to their eggs or chicks. While their management can be challenging and oftentimes frustrating but it is impossible to not admire the tenacity of this smallest species of tern!
Photos by: Stewart Ting Chong