font settings and languages

Font Size: Large | Normal | Small
Font Face: Verdana | Geneva | Georgia
Languages:

Sterna antillarum

(American Least Tern)

Overview

[ Back to top ]

The interior least tern is the smallest member of the tern family with a wingspan of 20 inches (50 cm). They have a grayish back and wings , and snowy white undersides. Least terns can be distinguished from all other terns by their combination of a black crown, white forehead, and a variable black-tipped yellow bill.

Many nesting areas have been permanently flooded by reservoirs and channelization projects. Unpredictable water discharge patterns below dams flood nesting areas. Overgrowth of brush and trees also eliminates remaining habitat . This prevents terns from using these areas as nesting sites. The recreational use of sandbars by humans is a major threat to the tern's reproductive success.

Interesting Facts

[ Back to top ]

Common Names

[ Back to top ]

Click on the language to view common names.

Common Names in Dutch:

Amerikaanse dwergstern

Common Names in English:

American Least Tern, Brown's tern, Least Tern

Common Names in French:

Petite Sterne

Common Names in German:

Amerikanische Zwergseeschwalbe

Common Names in Spanish:

Charr, Charrán mÌnimo

Common Names in unspecified:

California Least Tern

Description

[ Back to top ]

Physical Description

Adult : Head : Cap: black Face : Forehead: white Lores : black Bill: orange-yellow with dark tip Neck: Nape: black Body: Underparts: white Legs : Leg Color: orange-yellow Tail: Shape : deeply forked.

Color:

Adults : Black cap, nape, and eye stripe; white forehead, lower face , and underparts; gray wings amd tail; outer primaries (flight feathers) darker gray; bill, legs , and feet yellow. Juveniles : Mottled browns and grays above.

During breeding, the least tern has a white forehead. Juveniles and immatures are smaller and more difficult to identify.[1]

Adult alternate: Yellow legs · Yellow bill with tiny black tip · Black cap with white forehead patch before eye · White face, foreneck, breast, and belly · Pale gray rump and tail · Entirely gray back and upperwing with dark outer two primaries

Adult basic: Orange legs · Black bill · White forehead, face, foreneck, breast, and belly · Black cap mottled with white · Entirely gray back and upperwing with dark outer two primaries

Juvenile: Pale orange legs · Pinkish bill becomes black with age · White forehead, foreneck, breast, and belly · Black eye patch · Pale crown streaked with brown and black · Pale brown back with brownish center to feathers · Dark carpal bar · Gray wings with brown tips to upperwing coverts · Dark outer five primaries forms bold, dark, wedge in flight · Short tail with dark gray-brown tips

First winter/First summer: Black bill and legs · Black half hood · Pale forehead · Pale crown streaked with black · Dark carpal bar

Size/Age/Growth

About 8 to 9 inches long, with a wingspan of 20 to 20 inches. Adults weigh about 1.5 ounces .

Habitat

Interior least terns favor islands or sandbars along large rivers for nesting. The sand must be mostly clear of vegetation to be used by terns. Least terns prefer shallow water for fishing . Water levels must be low enough so that nests stay dry.

Vegetation: freshwater marshes, coastal waters, saltwater and brackish marshes • Foraging Strata: Water • Center of Abundance: Lower tropical: lowlands, lower than 500 m.; tropics. • Sensitivity to Disturbance: Medium

Typically found at an altitude of 0 to 2,911 meters (0 to 9,551 feet).[2]

Ecology: This species can be found on lakes , rivers and estuaries, strictly on the coast in some regions (e.g. California) but inland in others (e.g. Florida). It feeds on small fish fry, shrimps, marine worms and occasionally flying ants and other insects. Prey are usually caught by plunge-diving up to 10m, preceeded by prolonged hovering, and it also occasionally peforms surface-dipping and aerial hawking. The breeding season begins between April and mid-June depending on locality , and it breeds in a large variety of habitats , from baren sandy beaches to parking lots and roof tops. Individuals form colonies usually between 5 and 200 pairs strong . It is a highly migratory species, though some populations in the north of South America, and on the Pacific coast of Mexico may be year-round residents1.

[3].

List of Habitats:

[more info]

Biology

[ Back to top ]

Diet

Its diet consists of fish, aquatic invertebrates , and crustaceans. The Least Tern finds its food by searching while in flight and diving into the water to catch the prey .

Reproduction

The least tern nests on the ground , typically in areas that are sandy and relatively free of vegetation, such as sandbars in rivers , beaches, and spits in coastal areas. In New Mexico, and other parts of the southern Great Plains , alkali flats are selected as nesting areas. The nest is a shallow scrape, in which the eggs are laid. These are buff with irregular dark splotches and dots, and they average 1 1/2 inches in length . Seven clutches that were observed at Bitter Lake National Wildlife Refuge ranged from one to three eggs, with the average being two.[1]

The breeding season begins in May. Breeding habitat includes areas of sandy or gravel beaches along the coast, rivers, or lakes. The Least Tern nests in colonies. The nest scrape is built by the female in the sand or gravel and sometimes is lined with fine plant material . The female lays 1-3 (usually 2) eggs that she and the male incubate for 20-22 days. The young are semi-precocial and remain in the nesting area for 19-20 days. They are cared for by both adults during that time. Clutch Size: 2-3 Length of Incubation : 20-22 days Days to Fledge : 19-20+ Number of Broods: 1, occasionally 2 in south

Migration

Migratory

Behavior

Interior least terns arrive at breeding sites from late April to early June where they typically spend four to five months. Pairs go through an elaborate courtship period that includes courtship feedings and a variety of postures and vocalizations. Least terns nest in small colonies on exposed salt flats, river sandbars , or reservoir beaches. Nests are small scrapes in the sand , and usually two or three eggs are laid. The young are fairly mobile soon after hatching . Both parents feed the young and remain with them until fall migration. Terns will travel four or more miles (6+ km ) from their breeding colonies to find the small fish that make up the major part of their diet .

The calls of the lest tern include various kittering notes , a sharp "kit" and a harsh "zree-eek" or "zeek." [1]

Taxonomy

[ Back to top ]

Synonyms

Sterna antillarum (Lesson, 1847)

Notes

Name Status: Accepted Name .

Last scrutiny: 24-Jun-1996

Similar Species

[ Back to top ]

Black Tern

Members of the genus Sterna

ZipcodeZoo has pages for 63 species and subspecies in this genus:

S. acuticauda (Black-Bellied Tern) · S. albifrons (Little Striker) · S. albifrons albifrons (Little Tern) · S. albifrons athalassos (Little Tern) · S. albistriata (Black-Fronted Tern) · S. albostriata (Saunder's Little Tern) · S. aleutica (Aleutian Tern) · S. anaetheta (Bridled Tern) · S. anaethetus (Brown-Winged Tern) · S. anaethetus anaethetus (Brown-Winged Tern) · S. anaethetus recognita (Bridled Tern) · S. antillarum (American Least Tern) · S. antillarum albifrons (Little Tern) · S. antillarum antillarum (Least Tern) · S. antillarum athalassos (Interior Least Tern) · S. antillarum browni (California Least Tern) · S. aurantia (Indian River Tern) · S. balaenarum (Damara Tern) · S. bengalensis (Lesser Crester Tern) · S. bengalensis bengalensis (Lesser Crester Tern) · S. bergii (Greater Crested Tern) · S. bergii bergii (Greater Crested Tern) · S. bernsteini (Chinese Crested-Tern) · S. caspia (Caspian Tern) · S. caspia caspia (Caspian Tern) · S. dougallii (Roseate) · S. dougallii dougallii (Roseate Tern) · (Elegant Tern) · S. eurygnatha (Cayenne Tern) · S. forsteri (ForsterÌs Tern) · S. fuscata (Wide-Awake) · S. fuscata crissalis (Sooty Tern) · S. fuscata fuscata (Sooty Tern) · S. hirundinacea (South American Tern) · S. hirundo (Lake Erie Gull) · S. hirundo hirundo (Common Tern) · S. lorata (Peruvian Tern) · S. lunata (Grey-Backed Tern) · S. maxima (Royal Tern) · S. maxima maxima (Royal Tern) · S. melanogaster (Black-Bellied Tern) · S. nereis (Fairy Tern) · S. nereis nereis (Fairy Tern) · S. nilotica (Bulled-Billed Tern) · S. nilotica groenvoldi (Gull-Billed Tern) · S. nilotica nilotica (Gull-Billed Tern) · S. nilotica vanrossemi (Gull-Billed Tern) · S. paradisaea (Crimson-Billed Tern) · S. repressa (White-Cheeked Tern) · S. sandvicensis (Caribbean Tern) · S. sandvicensis eurygnatha (Sandwich Tern) · S. sandvicensis sandvicensis (Caribbean Tern) · S. saundersi (Saunders' Little Tern) · S. striata (White-Fronted Tern) · S. striata striata (White-Fronted Tern) · S. sumatrana (Black-Naped Tern) · S. sumatrana sumatrana (Black-Naped Tern) · S. superciliaris (Yellow-Billed Tern) · S. trudeaui (Snowy-Crowned Tern) · S. virgata (Kerguelen Tern) · S. vittata (Antarctic Tern) · S. vittata vittata (Antarctic Tern) · S. zimmermanni (Chinese Crested-Tern)

More Info

[ Back to top ]

Further Reading

[ Back to top ]

Notes

[ Back to top ]

Contributors

Data Sources

Accessed through GBIF Data Portal February 29, 2008:

Identifiers

Footnotes

  1. New Mexico Wildlife. New Mexico Department of Game and Fish Version of April 24, 2009. [back]
  2. Mean = 28.810 meters (94.521 feet), Standard Deviation = 45.060 based on 136,812 observations. Altitude information for each observation from British Oceanographic Data Centre. [back]
  3. BirdLife International 2009. Sterna antillarum. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 05 February 2012. [back]
Last Revised: 2012-07-14