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Cayenne Tern Sterna (sandvichensis) eurygnatha


Cayenne Tern from Barloventomagic.com
Photo: Barloventomagico (flickr)                                  

At a glance

White, crested tern nesting primarily along South American coast

First discovered to be breeding in the West Indies in 1962


Rare and considered critically endangered in the region

Taxonomic relationship with Sandwich Tern unresolved

Index



Identification:

White, thin billed tern with black crest (see Sandwich Tern).

Adults

Sexes alike, with seasonal plumage variation. Legs and bill yellow, but somewhat variable in color. Non-breeding adults have white foreheads and crown mottled with black and white. Outer-most three primaries blackish. Crest plumage is longer and more shaggy than that of Sandwich Tern.

Juveniles

Dorsal feathers with brown tips, distinct carpal bar on upper wing (absent in adults). Bill and legs olive brown. Outer 4-6 primaries dark grey.

Systematics

Often placed in the genus Thalasseus with other crested terns. Closely related to the more temperate Sandwich Tern. Many consider the Cayenne Tern of the southern Caribbean and South America to be a subspecies of the Sandwich Tern. These two terns are known to pair together and interbreeding has been reported. Varying percentages of populations are represented by birds with intermediate bill colors, suggesting introgression between S. eurygnata and acuflavida is widespread. This is not true of Cayenne Tern populations in Brazil and Argentina. This tern is treated separately here mostly because it is simpler for us to discuss distributions and conservation issues in individual accounts.

Likely locations

Most likely to be seen only near nesting sites in the Netherlands Antilles. Because of its sporadic appearance in various tern colonies in the region, large colonies should be checked for individual pairs of these birds.

Distribution

The Cayenne Tern occurs along the northern and eastern South American coast and also in Caribbean. Was not reported in the West Indies prior to 1962. It is not clear if they were overlooked or if these terns have recently expanded their breeding range northward. The latter is most likely as most breeding colonies unknown in region prior to the 1980s. Currently nest in Netherlands Antilles, islands off the Venezuelan coast, off Guyana and along the coast of Brazil and southern Argentina. Vagrants reported from in coastal North Carolina.

In West Indies nesting reported only from Puerto Rico, the US and British Virgin Islands and Trinidad.


Biology

At sea

Dispersal distances from colonies unknown; assumed to be a short-range migrant. Not studied in region. See Sandwich Tern.

At the nest

Little information. Colonial often nesting with other tern species. Avoids areas disturbed and where Laughing Gulls are nesting (Aruba). Colonies formed in fine sand with sparse vegetation. Eggs deposited second week in May, occasionally as early as 22 April. Chicks flock together at a few days of age (Aruba). Adults and chicks abandon colonies in late August to early September (Guyana). See Sandwich Tern.

Current Population 

Government

Breeding Sites

Low Estimate

High Estimate

Cuba

1

1

1

Dominican Republic

2

2

20

Puerto Rico

7

1

27

United States Virgin Islands

1

1

5

British Virgin Islands

2

3

7

Trinidad and Tobago

1

0

0

Venezuela

5

352

920

Bonaire

2

180

190

Curacao

3

0

0

Aruba

1

3226

3582

Guyana114002000
Total2651666752

Conservation Status

The Cayenne Tern is considered to be critically endangered in the West Indies (Schreiber and Lee 2000). Netherlands Antilles and South American population somewhat stable but small, perhaps declining as a result of egging, development and pollution (oil refineries).  

Conservation Needs

During surveys of tern colonies in the West Indies researchers should be aware that individual pairs of Cayenne Terns could be present.

Genetic studies to determine the relationship of this tern to Sandwich Terns needed. With the recent expansion of both Sandwich and Cayenne Terns into the region hybridization appears o be occurring. They have been seen paired with Sandwich Terns and hybrids have been reported. Reports of bill colors of nesting Sandwich and Cayenne Terns in various populations is useful.

Because of the rarity of this tern in the West Indies all known nesting sites deserve full protection. Laughing Gulls are an issue at many nesting sites.

Photos

Selected References:

Buckley, P. A. and F. G. Buckley. 1984. Cayenne Tern new to North America, with comments on its relationship to Sandwich Terns. Auk 101: 396-398.

Junge , G. C. A. and A. K. Voous. 1955. The distribution and relationship of Sterna eurygnatha Saunders. Ardea 43: 226-247.

Norton, R. L. Cayenex Sandwich terns nesting in the Virgin Islands, Greater Antilles. Journal Field Ornithology 55: 243-246.

Norton, R. L. 2000. Status and conservation of Sandwich and Cayenne Terns in the West Indies. Pages 80-83 in E. A. Schreiber and D. S. Lee (eds.) Status and Conservation of West Indian Seabirds. Society of Caribbean Ornithology, Special Publication Number 1.225 pp.

Schaffner, F. C., R. L. Norton and J. Taylor. 1986. Range extension of Cayenne terns on the Puerto Rico Bank. Wilson Bulletin 98(2): 317-318.

Shealer, D. 1999. Sandwich Tern (Sterna sandvicensis). in The Birds of North America, No. 405 (A. Poole and F. Gill. Eds.). The Birds of North America, Inc., Philadelphia.

Van Halewyn, R. and R. Norton. 1984.The status and conservation of seabirds in the Caribbean. Pages 169-222 in J. P. Croxall, P. G. Evans and R. W. Schreiber (eds). Status and Conservation of the World's Seabirds. ICBP Tech. Publ., No. 2. 778 p.

Compiled by: Dave Lee and Will Mackin

West Indian Breeding Seabird Atlas by Will Mackin and David Lee is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. Based on work at www.wicbirds.net. Permissions beyond the scope of this license may be available at www.wicbirds.net.

Suggested Citation: Lee, D. S., W. A. Mackin. 2009. Cayenne Tern. West Indian Breeding Seabird Atlas <http://www.wicbirds.net/cayt.html>. Last Updated: _____. Date accessed: ______.

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August 30, 2009
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