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.

View Implementation Actions for Least Terns

Show/Hide Table Data

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	1,070
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	250	526	776
2017	244	911	1,155
2018	62	996	1,058
2019	298	904	1,202
2020	299	759	1058
2021	311	459	770
2022	247	737	984
2023	329	441	770
2024	289

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
2995	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	7192
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 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 includes New York, Connecticut, 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.

Since the dismal shorebird nesting season of 2018, in which only 62 pairs attempted nesting and only 14 least tern chicks fledged, in recent years the number of least tern nesting pairs in Connecticut bounced back to at least 200 nesting attempts per year. It is currently not known why Connecticut experienced such a sharp decline in 2018. In 2020, 299 pairs fledged 71 young but, unfortunately in 2021, although 311 pairs nested, only 32 chicks fledged. Although the total number of least tern breeding pairs throughout the North Shore of Long Island had steadily increased from a low of 382 pairs in 2014 to a high of 996 attempted nests in 2018, the number of breeding pairs decreased over a three-year period from 2018 to 2021. But the steep decline in the least tern nesting success in Connecticut, and throughout the Northeast region, is 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 three-year period, New York numbers have consistently decreased while Connecticut numbers have stabilized.  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.

In addition to the noted breeding pairs, productivity rates of those pairs is essential to the success of the species. In 2023, Connecticut’s most successful site, in Groton, observed a productivity rate of 0.67. While this rate appears low least terns are long-lived birds and the Atlantic Coast population has remained stable. However, predation and/or human disturbance, such as off-leash dogs, continues to be a problem at most breeding sites in Connecticut.