Animal Diversity Web

Pele­can­i­formes com­prises six fam­i­lies (Phaethon­ti­dae (trop­icbirds), Sul­i­dae (boo­bies and gan­nets), Pha­lacro­co­raci­dae (cor­morants and shags), An­hingi­dae (an­hin­gas), Pele­canidae (pel­i­cans) and Fre­gati­dae (frigate­birds)), six gen­era, and 67 species.

Pele­can­i­form birds are dis­trib­uted world­wide, pri­mar­ily in coastal and ma­rine zones.

Pele­can­i­form birds in­habit ma­rine and in­land wa­ters. Habi­tat varies from pelagic to coastal to in­land fresh­wa­ter en­vi­ron­ments.

In­cu­ba­tion ranges from 25-55 days. Young are al­tri­cial and all chicks, ex­cept trop­icbirds, are born with­out natal down. Fledg­ing age is highly vari­able, rang­ing from 65-210 days. Post-fledg­ing care is pro­nounced and may last for as long as 18 months in some species. Age at first breed­ing varies with species and ranges from two to per­haps eleven years.

Pele­can­i­form birds are medium to large aquatic birds with toti­palmate feet (all four toes joined by web). Most have dis­ten­si­ble gular sac lo­cated be­tween the branches of the lower mandible. In trop­icbirds the small gular re­gion is feath­ered, in pel­i­cans the bare sac is pen­du­lous, and in frigate­birds the large, bare, red gular sac is in­flat­able. Only trop­icbirds have ex­posed ex­ter­nal nares. All pele­can­i­form birds' skulls lack supra­or­bital groove for a nasal gland and dor­sal ver­te­brae are opistho­coelous. Plumage ranges from mostly black with some white to mostly white with some black. Feet and bare re­gions of face and gular sac may be­come brightly col­ored dur­ing breed­ing. Most have desmog­nathous palate, ex­cept trop­icbirds, which have schizog­nathous palate. All ex­cept frigate­birds lack brood patches.

Many pele­can­i­forms breed in mixed colonies with other pele­can­i­forms, gulls, terns, or pen­guins.

Pele­can­i­form birds feed pri­mar­ily on fish and squid. They may also prey on mol­lusks, crus­taceans, am­phib­ians, rep­tiles, and in­ver­te­brates.

Preda­tors of pele­can­i­form birds in­clude hu­mans, birds, rats, cats, dogs, and rep­tiles.

Most pele­can­i­form birds are con­sid­ered sea­son­ally monog­a­mous. Nest-sites and mates may change from year to year, ex­cept per­haps for sulids. Mat­ing dis­plays and pair for­ma­tion be­hav­iors are elab­o­rate and com­plex. Gen­er­ally males dis­play to at­tract fe­males. Fe­males de­fend the nest-site and con­struct the nest from ma­te­ri­als col­lected by the male. Cop­u­la­tions gen­er­ally occur at the nest or dis­play site.

Breed­ing may be an­nual or bi­en­nial, sea­sonal or year round. Pele­can­i­form birds nest in colonies, some­times con­sist­ing of thou­sands of pairs. Nest sites are vari­able, lo­cated on the ground, in trees or shrubs, or on cliff ledges. Nests may be in­sub­stan­tial scrapes or con­struc­tions of twigs and other ma­te­ri­als. Clutch size varies with species and ranges from one to six eggs. Egg color ranges from white to pale green-blue to red-brown.

In pele­can­i­form birds both sexes take ap­prox­i­mately equal stints in­cu­bat­ing eggs. All species ex­cept the frigatids lack brood patches and use foot web­bing to trans­fer heat to eggs. Du­ra­tion of in­cu­ba­tion varies con­sid­er­ably from 24 -57 days. Both par­ents brood and feed chicks re­gur­gi­tated food. Many species have post-fledg­ing care where par­ents con­tinue to feed chicks, in some species post-fledg­ing care is pro­longed and may last for as long as 18 months.

Some pele­can­i­forms are mi­gra­tory whereas oth­ers are mostly seden­tary with wide dis­per­sal of young. All pele­can­i­forms are aquatic birds and as­so­ci­ated with large bod­ies of water. For­ag­ing tech­niques vary from hunt­ing singly to for­ag­ing co­op­er­a­tively in large groups, from plunge div­ing to sur­face div­ing, from un­der­wa­ter stalk­ing am­bushes to aer­ial and un­der­wa­ter pur­suit div­ing. Species with large gular sacs use them in con­junc­tion with for­ag­ing, mat­ing dis­plays and ther­moreg­u­la­tion.

Most pele­can­i­forms are gre­gar­i­ous, gath­er­ing in colonies for breed­ing and roost­ing in large groups.

Pele­can­i­forms are no­tably noisy when in large groups. Vo­cal­iza­tions are vari­able with species, and range from the sharp pierc­ing whis­tle of the trop­icbirds to the gut­tural grunt­ing of cor­morants.

Hu­mans ex­ploit pele­can­i­form birds ex­ten­sively. The eggs, chicks, and/or adults of many species are col­lected for con­sump­tion, pur­ported med­i­c­i­nal pur­poses, or for goods and cloth­ing. Hu­mans col­lect and sell pele­can­i­form guano as fer­til­izer. Some species are trained and used by hu­mans in con­junc­tion with fish­ing.

Twenty-two pele­can­i­form species are in­cluded in the IUCN Red List of Threat­ened Species.

One species, Pal­las's Cor­morant (Pha­lacro­co­rax per­spic­il­la­tus), is listed as 'Ex­tinct'; two are listed as 'Crit­i­cally En­dan­gered' (An­drew's Frigate­bird (Fre­gata an­drewsi) and Ab­bott's Booby (Pa­pa­sula ab­botti)); and two species are listed as 'En­dan­gered', (Flight­less Cor­morant (Pha­lacro­co­rax har­risi) and Chatham Is­land Shag (P. on­slowi)). Of the re­main­ing species, eleven are listed as 'Vul­ner­a­ble' and six are 'Lower Risk'. Major threats in­clude habi­tat de­struc­tion, in­tro­duced preda­tors, pes­ti­cide poi­son­ing and oil spills.

The evo­lu­tion­ary re­la­tion­ships of pele­can­i­form birds re­main un­clear and the mono­phyly of Pele­can­i­formes is strongly de­bated. Tra­di­tion­ally, Pele­can­i­formes (or Steganopodes) is a group com­pris­ing six fam­i­lies in­clud­ing:(Phaethon­ti­dae (trop­icbirds), Sul­i­dae (boo­bies and gan­nets), Pha­lacro­co­raci­dae (cor­morants and shags), An­hingi­dae (an­hin­gas), Pele­canidae (pel­i­cans) and Fre­gati­dae (frigate­birds). Analy­ses of mor­pho­log­i­cal and etho­log­i­cal ev­i­dence sug­gest that phaethon­tids are rel­a­tively prim­i­tive whereas frigatids are rel­a­tively most de­rived of the group. In con­trast, fos­sil ev­i­dence ap­pears to sup­port the hy­poth­e­sis that phaethon­tids and frigatids fall basal rel­a­tive to the rest of the group. Some mor­pho­log­i­cal ev­i­dence sup­ports the mono­phyly of Pele­can­i­formes and its sis­ter group re­la­tion­ships with pro­cel­lari­ids (al­ba­trosses, pe­trels, shear­wa­ters) and ci­coni­ids (storks, herons, ibises, spoon­bills). Some mol­e­c­u­lar, etho­log­i­cal, and mor­pho­log­i­cal ev­i­dence re­futes the mono­phyly of Pele­can­i­formes. One hi­er­ar­chy based on DNA hy­bridiza­tion places phaethon­tids sis­ter to a group com­pris­ing sulids, an­hingids, and pha­lacro­co­racids; pele­canids as sis­ter to a Shoe­bill Stork (Bal­aeni­ceps); and frigatids as sis­ter to sphenis­cids (pen­guins) and in­cluded in a group (Pro­cel­lar­i­oidea) along with gavi­ids (loons) and pro­cel­lari­ids (pe­trels, shear­wa­ters, al­ba­trosses).

The old­est pele­can­i­form fos­sils in­clude a phaethon­tid (Prophaethon) from Eng­land dat­ing from the early Eocene and a fre­gatid (Lim­nofre­gata) from Wyoming also dat­ing to the Eocene. Pha­lacro­co­racid fos­sils ex­tend back to the Eocene-Oligocene bound­ary.

Sulid (Sula ron­zoni) and pele­canid (Pele­canus gra­cilis) fos­sils from France date from the early Oligocene and lower Miocene re­spec­tively. Old and New world fos­sil an­hingids date from the early (An­hinga sub­volans) and the late (A. pan­non­ica, A. gran­dis) Miocene.

Camp­bell, B., and E. Lack, ed­i­tors. 1985. A Dic­tio­nary of Birds. Buteo Books, Ver­mil­lion, SD.

del Hoyo, J., El­liott, A. & Sar­gatal, J. (eds.) 1992. Hand­bood of the Birds of the World. Vol. 1. Lynx Edi­cions, Barcelona.

Fe­duc­cia, A. 1999. The Ori­gin and Evo­lu­tion of Birds, 2nd edi­tion. Yale Uni­ver­sity Press New Haven.

Johns­gard, P. A. 1993. Cor­morants, Darters, and Pel­i­cans of the World. Smith­son­ian In­sti­tu­tion Press Wash­ing­ton.

Sib­ley, C. G. & J. E. Ahlquist. 1990. Phy­logeny and Clas­si­fi­ca­tion of Birds, A Study in Mol­e­c­u­lar Evo­lu­tion. Yale Univ. Press.

Siegel-Causey, D. 1988. Phy­logeny of the Pha­lacro­co­raci­dae. Con­dor 90:885-905.

Van Tets, G. F. 1976. Aus­trala­sia and the ori­gin of shags and cor­morants, Pha­lacro­co­raci­dae. Pp. 121-24 in: Proc. 16th Inter. Or­nith. Congr. Can­berra, Aus­tralia, 1974.

Con­trib­u­tors

Laura Howard (au­thor), An­i­mal Di­ver­sity Web.