NYC Audubon Director of Conservation and Science Susan Elbin reports on our work with the New York State threatened Common Tern:
The common tern (Sterna hirundo), a native North American waterbird, was nearly extirpated from North America by the millinery trade in the late 19th century, and again by habitat loss and environmental contaminants in the mid-20th century. Thanks to the Migratory Bird Treaty Act and other conservation efforts and environmental regulations, this species has been brought back from the brink of extinction. But populations have not returned to historic levels. The common tern continues to be a threatened species in New York State, and maintaining current population levels requires management to protect the breeding population. The major threats to tern populations on their breeding grounds appear to be space limitation due to habitat destruction and competition with other waterbirds. Common terns are also threatened by specific consequences of climate changes such as warmer summers and severe storms that impact shoreline nesting areas.
Common terns have been nesting in the Jamaica Bay area for decades. Just recently, a colony has established itself on the decommissioned piers of Governors Island. Just a ferry ride from lower Manhattan, the birds can been seen plunge-diving for fish to feed their growing chicks.
While the majority of our conservation and monitoring efforts occurs during the breeding season, common terns spend less than one-third of the year on their breeding grounds. Threats during the other two-thirds of the year, during migration and wintering periods, are unknown. We have initiated two pilot studies using high-technology techniques: geolocators and nanotags. A geolocator is a tag that the bird wears around its leg. The tag can later be removed from the bird in order to download latitude/longitude data collected over the course of one year. Nanotags are small radio transmitters attached to a bird’s back that send a signal to stationary VHF towers installed along the eastern seaboard of the U.S. and across Canada. Results from these two projects will indicate where the birds have spent the winter and how long they stay in a given area, respectively. The goal is to determine what areas New York City common terns are using as stopover sites during migration and over the winter. We plan to expand this project in the coming years, working with partner organizations to increase the sample size and to collect more data about the trends in migratory and overwintering behavior as well as the amount of variation in this behavior within the population. Determining where these birds migrate and overwinter is the necessary first step in identifying threats to the population during these times of the year, when the majority of mortality likely takes place.
Join us for the “It’s Your Tern” festival on Governors Island this Saturday, July 16! Learn more here.