Animal Diversity Web

Ge­o­graphic Range

Greater shear­wa­ters are a ma­rine species dis­trib­uted through­out the re­gion of the At­lantic ocean. Puffi­nus gravis breed in the far south At­lantic, mainly on the is­lands of the Tris­tan da Cunha group, the Falk­land Is­lands, and Gough Is­land. P. gravis then mi­grates to the North At­lantic dur­ing the win­ter, reach­ing noth-east Canada and some­times reach­ing as far north as Green­land. Mi­gra­tion to the breed­ing grounds in­volves a flight east, past Britain and Iberia, than turn­ing south to reach their South­ern Hemi­sphere breed­ing grounds.

(del Hoyo, El­liot, and Sar­gatal 1992; Far­rand 1985; Good­ers 1978)

• Biogeographic Regions
• oceanic islands
  • native
• atlantic ocean
  • native

Habi­tat

P. gravis is a ma­rine, pelagic bird species, fre­quent­ing cool off­shore and pelagic wa­ters, and breed­ing on slop­ing ground, mainly in grass­land or wood­land areas (del Hoyo, El­liot, and Sar­gatal 1992; Good­ers 1978)

Phys­i­cal De­scrip­tion

Puffi­nus gravis is a large shear­wa­ter species, 43-51cm in length, with a wingspan of 100-118cm. Colour­ing is unique with a com­bi­na­tion of pale un­der­parts with a poorly de­fined dark patch on the belly. White bands of plumage occur across the up­per­tail-coverts and also across the hind­neck, em­pha­siz­ing the Greater Shear­wa­ters strongly capped ap­pear­ance. Up­per­parts are dark gray-brown to black with light feather edg­ings to give a scaled ap­pear­ance. Flight feath­ers have black up­per- and un­der­sur­faces. The tubenosed bill is long, thin, and black. The legs are pink to grey with webbed feet, and eyes are brown. Chicks have bluish-grey down and ju­ve­niles are sim­i­lar to adults but greyer with paler fringes to feath­ers to give less scaled ap­pear­ance. There is no sex­ual di­mor­phism in terms of size or colour be­tween males and fe­males.

(Camp­bell 1974; del Hoyo, El­liot, and Sar­gatal 1992; Far­rand 1985; Good­ers 1978)

• Other Physical Features
• endothermic
• bilateral symmetry

• Range mass

  715 to 950 g

  25.20 to 33.48 oz

Re­pro­duc­tion

The breed­ing sea­son com­mences in Oc­to­ber and often lasts until De­cem­ber. Breed­ing takes place in the South­ern Hemi­sphere and is re­stricted to the far south oceanic is­lands: Tris­tan da Cunha group, Falk­land Is­land, and Gough Is­land. Puffi­nus gravis is a colo­nial nester, nest­ing in bur­rows or crevices among boul­ders along hilly is­land shores. The fe­male pro­duces a sin­gle, white, oval, and slightly pointed egg. The egg is in­cu­bated for 53-57 days, and an al­tri­cial off­spring is then hatched. Both male and fe­male care for young. Off­spring be­come in­de­pen­dent of their par­ents at about 105 days. (del Hoyo, El­liot, and Sar­gatal 1992; Good­ers 1978)

• Key Reproductive Features
• iteroparous
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

Lifes­pan/Longevity

• Average lifespan
  Status: wild

  85 months

  Bird Banding Laboratory

Be­hav­ior

Greater Shear­wa­ters are a so­cial species, fly­ing, hunt­ing, and mi­grat­ing to­gether in flocks, and can often be seen as flocks fol­low­ing ships for food. They are ex­pert fly­ers with the ma­jor­ity of their life spent in flight. These birds take to the air by flap­ping and then soar using air cur­rents. The name 'shear­wa­ter' comes from the be­hav­iour of soar­ing just above the sur­face of the ocean, closely fol­low­ing the con­tour of the waves with their wings out­stretched, shear­ing the water sur­face with the pointed tips of the wings.

Puffi­nus gravis is also agile un­der­wa­ter, ca­pa­ble of ro­tat­ing 180 de­grees, using wings for ma­neu­ver­ing. These birds, de­spite their grace­ful ap­pear­ance in the air and under water, are clumsy and awk­ward on land.

Puffi­nus gravis is a transe­qua­to­r­ial mi­grant, breed­ing in the South­ern Hemi­sphere and win­ter­ing in the North­ern Hemi­sphere.

In­di­vid­u­als ex­hibit a harsh rau­cous call when feed­ing, much like a gull, and they also ex­hibit a vocal croak upon re­turn­ing to a nest at night. Calls are sex­u­ally di­mor­phic, the fe­males with shorter calls, and with a lower fre­quency in­spi­ra­tory phrase than the fre­quency of the first har­monic of the longer ex­pi­ra­tory phrase. This is re­versed in males. In­di­vid­u­als can dis­crim­i­nate be­tween fe­male and male calls which is po­ten­tially use­ful in mate se­lec­tion. Greater Shear­wa­ters are suf­fi­ciently large to be rel­a­tively se­cure from pre­da­tion by Great Skuas (Cathar­acta antarc­tica), a major preda­tor in this area. As a re­sult of this, Greater Shear­wa­ters have no noc­tur­nal habits as they can dis­play dur­ing the day.

(Brooke 1988; Brown, Bourne, and Wahl 1978; del Hoyo, El­liot, and Sar­gatal 1992; Good­ers 1978)

• Key Behaviors
• flies
• motile

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Greater Shear­wa­ters feed in groups where ag­gres­sive in­traspe­cific feed­ing com­pe­ti­tion is ev­i­dent through lash­ing with bills and wings. They eat mostly fish and squid, with oc­ca­sional feed­ing on crus­taceans, fish en­trails, and other refuse dis­carded by fish­ing ves­sels. They hunt by plunge-div­ing from heights of 6-10m or tak­ing prey from sur­face seiz­ing or pur­suit div­ing.

Sur­face-seiz­ing con­sists of the 'walk­ing on water' that is usu­ally as­so­ci­ated with Storm Pe­trels. With­out en­tirely fold­ing its wings, a Greater Shear­wa­ter lands on the water sur­face with its feet, bal­ances with its wings, and "walks" for­ward over the water as it picks up food from near the sur­face.

Plunge-div­ing in­volves strik­ing the water sur­face from heights of 6-10 m with belly and feet and then in­stantly low­er­ing the head under the water sur­face to lead into a smooth sub­mer­sion. Oc­ca­sion­ally, a Greater Shear­wa­ter might briefly halt 0.5 m above the water sur­face, spread its feet, then plunge head­first un­der­neath the water. After the dive, the bird bursts out of the water and al­most di­rectly into flight.

(Brown, Bourne, and Wahle 1978; del Hoyo, El­liot, and Sar­gatal 1992; Good­ers 1978)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

In the past, Greater Shear­wa­ters had been used to pro­vide food and bait for sea­men, but this prac­tice has long since been dis­carded and aside from the oc­ca­sional con­tact with fish­er­men, and Tris­tan is­landers, P. gravis has mostly no con­tact with hu­mans.

(del Hoyo, El­liot, and Sar­gatal 1992; Cas­sidy 1990)

Con­ser­va­tion Sta­tus

Greater Shear­wa­ters are not glob­ally threat­ened. They are abun­dant with enor­mous total pop­u­la­tions of a min­i­mum 5 mil­lion breed­ing pairs on Tris­tan da Cunha, 600,000 to 3 mil­lion pairs on Gough Is­land, and small num­bers on Falk­land Is­lands. Their breed­ing range is re­stricted with only 4 sites known. Where the prob­lem lies is with ex­ploita­tion by Tris­tan is­landers. Each year, a few thou­sand adults, and 50,000 chicks are taken. This could lead to a pop­u­la­tion col­lapse un­less a quota sys­tem is es­tab­lished to allow for ra­tio­nal ex­ploita­tion. More re­search is re­quired in this area, as well as in the areas of the im­pact of har­vest­ing on Greater Shear­wa­ters, and the im­por­tance of other causes of mor­tal­ity and pop­u­la­tion dy­nam­ics, in order to de­ter­mine the max­i­mum sus­tain­able lev­els of ex­ploita­tion. An­other issue to be ad­dressed is that of the oc­ca­sional Greater Shear­wa­ter that is snared by fish­er­men's baited hooks.

Very lit­tle re­search has been done, but is re­quired to en­sure the main­te­nance of healthy pop­u­la­tions of Puffi­nus gravis world­wide.

(del Hoyo, El­liot, and Sar­gatal 1992)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Maryanne Spady (au­thor), Uni­ver­sity of Al­berta, Cindy Paszkowski (ed­i­tor), Uni­ver­sity of Al­berta.

Ref­er­ences

Brooke, M. 1988. Sex­ual Di­mor­phism in the Voice of Greater Shear­wa­ters. Con­dor, 100(2): 319-323.

Brown, R., W. Bourne, T. Wahl. 1978. Div­ing by Shear­wa­ters. Con­dor, 80: 123-125.

Camp­bell, B. 1974. The Dic­tio­nary of Birds in Colour. Lon­don: Michael Joseph Ltd.

Cas­sidy, J. 1990. Book of North Amer­i­can Birds. Mon­treal: Reader's Di­gest As­so­ci­a­tion, Inc..

Far­rand, Jr., J. 1985. The Audubon So­ci­ety Mas­ter Guide to Bird­ing. New York: Al­fred A. Knopf, Inc..

Good­ers, J. 1978. The Orbis En­cy­clo­pe­dia of Birds of Britain and Eu­rope-Birds of Ocean and Es­tu­ary. Lon­don: Orbis Pub­lish­ing.

del Hoyo, J., A. El­liot, J. Sar­gatal. 1992. Hand­book of the Birds of the World Vol­ume 1. Barcelona: Lynx Edi­cions.