Ecosystem Targets and Supporting Indicators
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The least tern (Sternula antillarum) is the smallest of American terns. They are migratory birds that winter in Central America, the Caribbean, and Northern South America. Breeding colonies appear along with either marine or estuarine shores of the coastal United States, or on sandbar islands in large rivers throughout the interior of the United States. The least tern hunts primarily in shallow estuaries and lagoons, where small fish are abundant. Once they have spotted their prey they plunge into the water in a spectacular aerial dive to catch it. The least tern’s favored nesting habitat is prized for human recreation, residential development, and alteration by water diversion, which interferes with successful nesting in many areas.
The abundance of least terns indicates whether there is sufficient protected beach habitat for coastal birds and sufficient food supply of forage fish in coastal waters.
Least terns, a threatened species in New York and Connecticut, live in large colonies on the beach and plunge into nearby waters for food. Predators, human disturbances, and tidal flooding can disrupt tern nesting sites, but the terns have the potential to recolonize in other beaches within a four-state region that also includes Rhode Island and Massachusetts. The least tern population has remained relatively stable among the southern New England/New York region since 1990. In 2011, there were 7,078 least tern pairs in the region, 735 pairs above the 20-year average.
In 2018, after several years of general stability, the least tern nesting season in Connecticut was dismal. During the 2018 shorebird nesting season, 236 adult least terns were observed in Connecticut but only 62 pairs attempted nesting from which 18 chicks hatched and only 14 least tern chicks fledged. That is living long enough to take flight. The least tern is a state threatened species in CT. In 2017, approximately 244 pairs of least terns nested along the shoreline in Connecticut, continuing a relatively stable four year average of 250 nesting attempts. The largest number of terns were found at Sandy Point in West Haven where more than 400 adults were observed there in May and June. Although the total number of least tern breeding pairs throughout the North Shore of Long Island has declined since 2006, the number of breeding pairs has been steadily increasing over the past four years. It is currently not known why CT experienced such a sharp decline in 2018. But the steep decline in the least tern nesting success in Connecticut, and throughout the Northeast region, is currently being investigated by wildlife managers of a northeast multi-state Least Tern Working Group working with the US Fish & Wildlife Service (USFWS). During this same five year period, New York numbers have consistently increased while CT numbers have decreased. The data suggests that some birds may favor one side of Long Island Sound from year to year, depending on available habitat and storm-damaged areas.