Sterna sandvicensisSandwich tern

Ge­o­graphic Range

Sterna sand­vi­cen­sis is con­sid­ered a strictly coastal species al­though it may fly over large land masses dur­ing mi­gra­tion and in­hab­its some large in­land lakes. In the Amer­i­cas sand­wich terns can be found as far north as the state of Vir­ginia in the United States and ex­tend south­ward to the north­ern­most parts of Chile on the west­ern coast of South Amer­ica and down to the south­ern reaches of Ar­gentina along the east coast of the con­ti­nent. In the Old World, sand­wich terns can be found as far north as south­ern Swe­den, ex­tend­ing south and west along the coast and wrap­ping around the tip of South Africa. Pop­u­la­tions also exist in the Black and Caspian Seas, along the Per­sian Gulf and in Kenya, Tan­za­nia and Dji­bouti in east­ern Africa. (Birdlife In­ter­na­tional, 2009)

Habi­tat

Sand­wich terns in­habit a va­ri­ety of habi­tats in­clud­ing sandy or rocky oceanic beaches, oceanic cliff sides, es­tu­ar­ies and large in­land lakes. Pre­ferred nest­ing sites are usu­ally sandy beaches with lit­tle or sparse veg­e­ta­tion or bare rock out­crops. (Birdlife In­ter­na­tional, 2009; Visser and Pe­ter­son, 1994)

Phys­i­cal De­scrip­tion

Sand­wich terns are medium-sized terns best iden­ti­fied by hav­ing a straight, slen­der black bill with a yel­low tip and a black crown with a short crest. The un­der­parts, rump and forked tail are white while the long, pointed wings and back are ash gray. The legs and webbed feet are black but can be vary­ing de­grees of yel­low in one sub­species found in South Amer­ica and the Caribbean. In non-breed­ing (win­ter) plumage the crown is mot­tled black and white to nearly all white and oc­ca­sion­ally has black wing mark­ings. In many mi­gra­tory birds this change in plumage is thought to func­tion as a sign to other birds of the same and sim­i­lar species that the in­di­vid­ual is not re­cep­tive to breed­ing.

Sand­wich terns weigh be­tween 130 and 311 g. They range from 36 to 46 cm in length and have a wingspan of 86 to 105 cm. (Birdlife In­ter­na­tional, 2009; Voelker, 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    130 to 311 g
    4.58 to 10.96 oz
  • Range length
    36 to 46 cm
    14.17 to 18.11 in
  • Range wingspan
    86 to 105 cm
    33.86 to 41.34 in

Re­pro­duc­tion

Sand­wich terns mate in monog­a­mous pairs within large, densely packed nest­ing colonies that can reach num­bers in the tens of thou­sands. This species typ­i­cally nests along­side other species, most no­tably the com­mon black-headed gull in west­ern Eu­rope. Often Sterna sand­vi­cen­sis does not ini­tially col­o­nize a given area, rather it does not ar­rive until an­other species has al­ready done so.

Upon ar­rival to colo­nial sites, adult birds will begin their rit­u­als of at­tract­ing a mate or re-es­tab­lish a re­la­tion­ship with a pre­vi­ous part­ner. Courtship dis­plays in­clude a male catch­ing one or more fish and lin­ing them side-by-side in its bill and pre­sent­ing them to the fe­male. She may im­me­di­ately con­sume the fish or the two may en­gage in an aer­ial dis­play soon after the ini­tial pre­sen­ta­tion. Cop­u­la­tion in this fam­ily of birds is done by the male mount­ing be­hind the fe­male on one side. The fe­male will move her tail to the op­po­site side and the male will try to en­gage cloa­cal con­tact while using his wings to awk­wardly main­tain bal­ance. (Birdlife In­ter­na­tional, 2009; Fa­sola and Canova, 1992; Fuchs, 1977)

Suit­able nest­ing habi­tats in­clude sandy or muddy beaches and open rock out­crops. Sand­wich terns often re­turn to colo­nial sites they have pre­vi­ously oc­cu­pied be­fore un­less the habi­tat is deemed un­suit­able. Nest sites are typ­i­cally higher above the high tide line than the amount of ground ac­tu­ally avail­able. Veg­e­ta­tion is gen­er­ally avoided and mat­ing pairs may aban­don their nest sites if grow­ing veg­e­ta­tion in­vades. In­di­vid­ual nests are sim­ple con­cave scrapes in the sub­strate often lined with ex­cre­ment.

Fe­male sand­wich terns lay 1 to 3 eggs per breed­ing sea­son that in­cu­bate for 21 to 29 days. Birds at higher lat­i­tudes often begin lay­ing eggs in May whereas lower lat­i­tudes begin in De­cem­ber. At hatch­ing the young weigh 22 to 24 g. After 7 to 14 days some colonies will form crèches where young birds gather in large groups when par­ents are ab­sent in order to gain safety in num­bers. The abil­ity to fly, or fledg­ing, comes after 28 to 35 days. Dur­ing their first year, young sand­wich terns learn to catch food on their own by watch­ing adults and prac­tic­ing. Prac­tice may in­clude div­ing for ac­tual food items or inan­i­mate ob­jects in order to gain ac­cu­racy. Sand­wich terns reach sex­ual ma­tu­rity at 3 to 4 years old. (Birdlife In­ter­na­tional, 2009; Fa­sola and Canova, 1992; Visser and Pe­ter­son, 1994)

  • Breeding interval
    Sandwich Terns breed once yearly.
  • Breeding season
    Sandwich Terns breed in the summer.
  • Range eggs per season
    1 to 3
  • Average eggs per season
    1-2
  • Range time to hatching
    21 to 29 days
  • Range fledging age
    28 to 35 days
  • Average time to independence
    1 years
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Range age at sexual or reproductive maturity (male)
    3 to 4 years

After eggs have been laid, both par­ents share in­cu­bat­ing re­spon­si­bil­i­ties. Both par­ents take turns pro­tect­ing the nest or for­ag­ing for the young. Par­ents con­tinue to feed young until they are fledged and able to gather food on their own. After 7 to 14 days some colonies will form crèches where young birds gather in large groups when par­ents are ab­sent in order to gain safety in num­bers. (Birdlife In­ter­na­tional, 2009; Dunn, 1972; Fuchs, 1977; Stienen, et al., 2001)

  • Parental Investment
  • precocial
  • male parental care
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • male
      • female
  • pre-hatching/birth
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifes­pan/Longevity

The old­est recorded sand­wich tern lived to be 23 years and 7 months. (Birdlife In­ter­na­tional, 2009)

  • Average lifespan
    Status: captivity
    23.58 years

Be­hav­ior

These birds are often silent much of the time and are usu­ally only no­ticed by sight. They can be fre­quently seen fly­ing along the shal­lows of a coast­line and oc­ca­sion­ally dive-bomb­ing prey. When rest­ing they will often form small groups and face away from the wind. If a neigh­bor gets too close short squab­bles tend to un­fold until one as­sumes dom­i­nance. This species is mi­gra­tory, some­times trav­el­ing great dis­tances from breed­ing to win­ter­ing grounds. Mi­gra­tion may be south­ward or north­ward de­pend­ing on the lo­ca­tion of breed­ing grounds. In­di­vid­u­als that breed in west­ern Eu­rope will travel south along the west­ern coast of Africa. In­di­vid­u­als from the Black Sea will stay in the Black Sea or move to the Mediter­ranean. Caspian Sea in­di­vid­u­als win­ter in the north­ern In­dian Ocean and Per­sian Gulf. North Amer­i­can in­di­vid­u­als travel south to the Caribbean and down through Cen­tral and South Amer­ica. (Birdlife In­ter­na­tional, 2009)

Home Range

Trav­el­ing 10 to 15 km per day in search of food is com­mon in this species with re­ports ex­tend­ing as far as 70 km per day. (Birdlife In­ter­na­tional, 2009)

Com­mu­ni­ca­tion and Per­cep­tion

It may be in­ferred from the stud­ies on royal terns that nest­ing adult sand­wich terns are able to dis­tin­guish their own eggs by vi­sual cues alone. Sand­wich terns are able to rec­og­nize their own young by vi­sual cues and vo­cal­iza­tions. Young are often called out of a crèche by par­ents, show­ing that the young can also iden­tify their par­ents by vo­cal­iza­tion. Sand­wich terns per­ceive their en­vi­ron­ment through vi­sual, tac­tile, au­di­tory, and chem­i­cal stim­uli. (Hutchi­son, et al., 1968)

Food Habits

Sand­wich terns are known to eat reef sil­ver­side, dwarf round her­ring, At­lantic thread her­ring, hard­head sil­ver­side, scaly sar­dines, com­mon an­chovies, mack­erel, jacks, fly­ing fish, dam­selfish, par­rot­fish, At­lantic her­ring, sprat, lesser sand eel and squid. The adults feed chicks dif­fer­ent prey species than they them­selves pre­fer to eat. It is not clear if this is due to dif­fer­ent di­etary needs of young ver­sus adults. In in­stances where this species has be­come ac­cus­tomed to human in­ter­ac­tion, adults will oc­ca­sion­ally ac­cept bread. (Shealer, 1998; Stienen and Bren­ninkmei­jer, 2002)

These birds typ­i­cally do not form large feed­ing flocks but will gather in small groups or hunt alone. They fly sev­eral me­ters above the water while for­ag­ing for prey. Once prey item is spot­ted they first hover above with beaks aimed di­rectly down­ward in order to set their aim then dive-bomb into the water. First-win­ter birds are often less suc­cess­ful in catch­ing food for them­selves than older adults. (Dunn, 1972; Shealer, 1998)

  • Animal Foods
  • fish
  • mollusks

Pre­da­tion

Short-eared owls, car­rion crows, her­ring gulls, great black-backed gulls, foxes, and stoats are preda­tors of chicks while com­mon black-headed gulls prey mostly on eggs. Sand­wich terns dis­play lit­tle ag­gres­sive anti-preda­tor be­hav­iors. Densely sit­u­ated nest­ing sites with more ag­gres­sive species of bird tend to al­le­vi­ate the ne­ces­sity for de­fen­sive be­hav­iors. If nec­es­sary, sand­wich terns will show de­fen­sive dis­plays in­volv­ing spread­ing their wings and rais­ing their bod­ies to ap­pear larger and mob­bing or dive-bomb­ing po­ten­tial preda­tors. Most of this ag­gres­sive be­hav­ior is seen dur­ing the breed­ing sea­son when chicks are be­gin­ning to hatch. (Fuchs, 1977)

Ecosys­tem Roles

There ap­pears to be a mu­tu­al­ism be­tween sand­wich terns and com­mon black-headed gulls where the lat­ter pro­vides pro­tec­tion from preda­tors while oc­ca­sion­ally eat­ing the eggs and steal­ing prey items of the for­mer. (Stienen and Bren­ninkmei­jer, 2002; Stienen, et al., 2001)

Mu­tu­al­ist Species

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

In­shore fish­er­man will often look for div­ing terns in order to lo­cate small bait­fish.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of sand­wich terns on hu­mans.

Con­ser­va­tion Sta­tus

This is a species of Least Con­cern from the In­ter­na­tional Union of the Con­ser­va­tion of Na­ture due to its large num­bers and ge­o­graphic dis­tri­b­u­tion. The suit­abil­ity of a given habi­tat for cre­at­ing nest­ing colonies of sand­wich terns is vul­ner­a­ble to de­struc­tion by nat­ural phe­nom­ena events (ie: hur­ri­canes, storms) and veg­e­ta­tion over­growth. Habi­tat de­struc­tion by hu­mans is known to ad­versely af­fect the abil­ity of this species and many oth­ers that de­pend on undis­turbed beach to breed. Overuse by hu­mans vis­it­ing beaches can cause whole colonies to aban­don the area en masse and min­i­mize re-use in fu­ture years. (Visser and Pe­ter­son, 1994)

Other Com­ments

In 2009 a DNA study sep­a­rated the three sub­species of Sterna sand­vi­cen­sis into two dis­tinct species. The North Amer­i­can forms are com­bined as one under the name Tha­lasseus acu­flavidus and the Eu­ro­pean form as Tha­lasseus sand­vi­cen­sis. As of yet this sug­ges­tion has not been fully adopted by the sci­en­tific com­mu­nity. (Efe, et al., 2009)

Con­trib­u­tors

Robert Gundy (au­thor), Florida State Uni­ver­sity, Emily DuVal (ed­i­tor), Florida State Uni­ver­sity, Rachelle Ster­ling (ed­i­tor), Spe­cial Pro­jects.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

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Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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Neotropical

living in the southern part of the New World. In other words, Central and South America.

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Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

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Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

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oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

Ref­er­ences

Birdlife In­ter­na­tional, 2009. "Sterna sand­vi­cen­sis" (On-line). IUCN Red List of Threat­ened Species. Ac­cessed Jan­u­ary 14, 2010 at http://​www.​iucnredlist.​org/​apps/​redlist/​details/​144242/​0.

Buck­ley, P., F. Buck­ley. 1972. In­di­vid­ual Egg and Chick Recog­ni­tion By Adult Royal Terns (Sterna max­ima max­ima). An­i­mal Be­hav­iour, 20: 457-462.

Dunn, E. 1972. Ef­fect of Age on the Fish­ing Abil­ity of Sand­wich Terns Sterna sand­vi­cen­sis. Ibis, Vol. 114, Issue 3: 360-366.

Efe, M., E. Tavares, A. Baker, S. Bon­atto. 2009. Multi­gene phy­logeny and DNA bar­cod­ing in­di­cate that the Sand­wich tern com­plex (Tha­lasseus sand­vi­cen­sis, Lar­i­dae, Stern­ini) com­prises two species. Mol­e­c­u­lar Phy­lo­ge­net­ics and Evo­lu­tion, Vol. 52, Issue 1: 263-267.

Fa­sola, M., L. Canova. 1992. Nest Habi­tat Se­lec­tion by Eight Syn­topic Species of Mediter­ranean Gulls and Terns. Colo­nial Wa­ter­birds, Vol. 15, No. 2: 169-178.

Fuchs, E. 1977. Pre­da­tion and Anti-Preda­tor Be­hav­iour in a Mixed Colony of Terns Sterna sp. and Black-headed Gulls Larus ridi­bun­dus with Spe­cial Ref­er­ence to the Sand­wich Tern Sterna sand­vi­cen­sis. Ornis Scan­di­nav­ica, Vol. 8, No. 1: 17-32.

Gochfeld, M., J. Burger. 1996. Fam­ily Stern­idae (Terns). Pp. 647 in J del Hoyo, A El­liott, J Sar­gatal, eds. Hand­book of the Birds of the World, Vol. 3. Hoatzins to Auks. Barcelona: Lynx Edi­cions.

Hutchi­son, R., J. Steven­son, W. Thorpe. 1968. The Basis for In­di­vid­ual Recog­ni­tion by Voice in the Sand­wich Tern (Sterna sand­vi­cen­sis). Be­hav­iour, Vol. 32, No. 1: 150-157.

Shealer, D. 1998. Dif­fer­ences in Diet and Chick Pro­vi­sion­ing be­tween Adult Roseate and Sand­wich Terns in Puerto Rico. The Con­dor, Vol. 100, No. 1: 131-140.

Stienen, E., A. Bren­ninkmei­jer, C. Geschiere. 2001. Liv­ing with Gulls: The Con­se­quences for Sand­wich Terns of Breed­ing in As­so­ci­a­tion with Black-headed Gulls. The In­ter­na­tional Jour­nal of Wa­ter­bird Bi­ol­ogy, Vol. 24, No. 1: 68-82.

Stienen, E., A. Bren­ninkmei­jer. 2002. For­ag­ing De­ci­sions of Sand­wich Terns in the Pres­ence of Klep­topar­a­sitis­ing Gulls. The Auk, Vol. 119, No. 2: 473-486.

Visser, J., G. Pe­ter­son. 1994. Breed­ing Poplu­a­tions and Colony Site Dy­nam­ics of Seabirds Nest­ing in Louisiana. Colo­nial Wa­ter­birds, Vol. 17, No. 2: 146-152.

Voelker, G. 1996. An Hy­poth­e­sis for Sea­sonal Color Change in the Genus Sterna. Jour­nal of Avian Bi­ol­ogy, Vol. 27, No. 3: 257-259.