Ecosystem Targets and Supporting Indicators

Least Terns

The least tern is the smallest of American terns. They are migratory birds that breed along marine and estuarine shores of the United States. Their abundance indicates the quality of coastal habitat and quantity of forage fish available for food.

Show/Hide Table Data

Least Terns (Breeding Pairs)
CTNYTotal
1991627-
1992655-
1993175-
1994334-
1995538-
1996461-
1997403-
1998447-
1999335-
2000239541780
20011758281,003
2002224767991
2003197650847
2004158548706
20052468241,070
20061441,2111,355
2007147691838
20082521,0731,325
200990843933
20101191,0001,119
20113599541,313
2012350585935
20135308331,363
2014257382639
2015241407648
2016250526776
20172449111,155
2018629961,058
2019904
4-State Least Terns (Breeding Pairs)
MANYCTRITotal
1992264224606552125969
1993262230331751756005
1994261725473342165714
2995275635205381356949
1996267330934612786505
1997319425604032626419
1998308524854475256542
1999341622613352976309
2000326721032392725881
2001342127391751906525
2002279632672241726459
2003249626781972395610
2004269120691582485166
2005265733822462146499
2006261527981442105767
2007311027921472356284
2008377636692522157192
200935692817901186594
2010348428321196437078
2011430926223591837473

WHAT IS THE LEAST TERN?

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.

WHAT DOES THIS INDICATE?

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.

STATUS

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.

DATA NOTES

  • The New York dataset for this indicator includes monitored sites on the North Shore of Long Island (Long Island Sound) and additional sites in Peconic Bay and Shelter Island in the North Fork of Long Island. LISS assesses this entire sub-region of Long Island for the least tern indicator because the birds frequently re-nest and might move from a Peconic Bay or Shelter Island beach to a Long Island Sound beach and back in the course of a year. LISS also maintains the same dataset for its other beach-nesting indicator, piping plovers.
  • New York data from 1990 to 2001 is currently not available.

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