Photos of the Long Island Sound

Research & Monitoring

Status and Trends: LISS Environmental Indicators

Least Terns

CTDEEP Wildlife Division and NYSDEC

Least Terns (Breeding Pairs)
CT NY Total
1991 627  —
1992 655  —
1993 175  —
1994 334  —
1995 538  —
1996 461  —
1997 403  —
1998 447  —
1999 335  —
2000 239   541    780
2001 175   828 1,003
2002 224   767   991
2003 197   650   847
2004 158   548   706
2005 246   824 1070
2006 144 1,211 1,355
2007 147    691    838
2008 252 1,073 1,325
2009   90     843    933
2010 119 1,000 1,119
2011 359     954  1,313
2012 350     585     935
2013 530     833  1,363
2014 257     382      639
2015  241     407  648
2016     526
4-State Least Terns (Breeding Pairs)
MA NY CT RI Total
1992 2642 2460 655 212 5969
1993 2622 3033 175 175 6005
1994 2617 2547 334 216 5714
1995 2756 3520 538 135 6949
1996 2673 3093 461 278 6505
1997 3194 2560 403 262 6419
1998 3085 2485 447 525 6542
1999 3416 2261 335 297 6309
2000 3267 2103 239 272 5881
2001 3421 2739 175 190 6525
2002 2796 3267 224 172 6459
2003 2496 2678 197 239 5610
2004 2691 2069 158 248 5166
2005 2657 3382 246 214 6499
2006 2615 2798 144 210 5767
2007 3110 2792 147 235 6284
2008 3776 3669 252 215 7912
2009 3569 2817 90 118 6594
2010 3484 2832 119 643 7078
2011 4309 2622 359 183 7473

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 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?

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 2011, after several years of  general decline, the least tern count in Connecticut was considerably higher than in the two years prior and this higher number of terns is encouraging (although it may show up as a decrease in a neighboring state). In 2011, approximately 361 pairs of least terns nested along the shoreline in Connecticut, an increase of 401 percent increase from 2009 when there were 90 pairs. 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. In New York, the total number of least tern breeding pairs throughout the North Shore of Long Island has been declining over the last ten years. This trend is similar to the overall decline across Long Island as a whole.

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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Barrier beach habitat is an important breeding ground for many coastal birds. The photo shows least terns at one of these beaches, Sandy Point in West Haven, Connecticut. The least tern is considered a threatened species in New York and Connecticut. Photo by Julian Hough.

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