Pelecaniformes

The Pelecaniformes are an order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such names as totipalmates or steganopodes. Most have a bare throat patch (gular patch), and the nostrils have evolved into dysfunctional slits, forcing them to breathe through their mouths. They also have a pectinate nail on their longest toe. This is shaped like a comb and is used to brush out and separate their feathers. They feed on fish, squid, or similar marine life. Nesting is colonial, but individual birds are monogamous. The young are altricial, hatching from the egg helpless and naked in most. They lack a brood patch.

The Fregatidae (frigatebirds), Sulidae (gannets and boobies), Phalacrocoracidae (cormorants and shags), Anhingidae (darters), and Phaethontidae (tropicbirds) were traditionally placed in the Pelecaniformes, but molecular and morphological studies indicate they are not such close relatives. They have been placed in their own orders, Suliformes and Phaethontiformes, respectively.[1]

Pelecaniformes
Temporal range: Late Cretaceous–recent, 66–0 Ma
Pelican 4995
Brown pelican (Pelecanus occidentalis)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Clade: Aequornithes
Order: Pelecaniformes
Sharpe, 1891
Families

Systematics and evolution

Classically, bird relationships were based solely on morphological characteristics. The Pelecaniformes were traditionally—but erroneously—defined as birds that have feet with all four toes webbed (totipalmate), as opposed to all other birds with webbed feet where only three of four were webbed. Hence, they were formerly also known by such names as totipalmates or steganopodes. The group included frigatebirds, gannets, cormorants, anhingas, and tropicbirds.[2]

Sibley and Ahlquist's landmark DNA-DNA hybridisation studies (see Sibley-Ahlquist taxonomy) led to them placing the families traditionally contained within the Pelecaniformes together with the grebes, cormorants, ibises and spoonbills, New World vultures, storks, penguins, albatrosses, petrels, and loons together as a subgroup within a greatly expanded order Ciconiiformes, a radical move which by now has been all but rejected: their "Ciconiiformes" merely assembled all early advanced land- and seabirds for which their research technique delivered insufficient phylogenetic resolution.

Morphological study has suggested pelicans are sister to a gannet-cormorant clade, yet genetic analysis groups them with the hamerkop and shoebill, though the exact relationship between the three is unclear.[3] Mounting evidence pointed to the shoebill as a close relative of pelicans.[2] This also included microscopic analysis of eggshell structure by Konstantin Mikhailov in 1995, who found that the shells of pelecaniform eggs (including those of the shoebill but not the tropicbirds) were covered in a thick microglobular material.[4] Reviewing genetic evidence to date, Cracraft and colleagues surmised that pelicans were sister to the shoebill with the hamerkop as the next earlier offshoot.[5] Ericson and colleagues sampled five nuclear genes in a 2006 study spanning the breadth of bird lineages, and came up with pelicans, shoebill and hamerkop in a clade.[6] Hackett and colleagues sampled 32 kilobases of nuclear DNA and recovered shoebill and hamerkop as sister taxa, pelicans sister to them, and herons and ibises as sister groups to each other with this heron and ibis group a sister to the pelican/shoebill/hamerkop clade.[7]

The current International Ornithological Committee classification has pelicans grouped with the shoebill (Balaenicipitidae), hamerkop (Scopidae), ibises and spoonbills (Threskiornithidae), and herons, egrets and bitterns (Ardeidae).[8]

Pelecaniformes

Threskiornithidae

Ardeidae

Scopidae

Balaenicipitidae

Pelecanidae

Recent research strongly suggests that the similarities between the Pelecaniformes as traditionally defined are the result of convergent evolution rather than common descent, and that the group is paraphyletic.[9] All families in the traditional or revised Pelecaniformes except the Phalacrocoracidae have only a few handfuls of species at most, but many were more numerous in the Early Neogene. Fossil genera and species are discussed in the respective family or genus accounts; one little-known prehistoric Pelecaniforms, however, cannot be classified accurately enough to assign them to a family. This is "Sula" ronzoni from Early Oligocene rocks at Ronzon, France, which was initially believed to be a sea-duck and possibly is an ancestral Pelecaniform.

The pelecaniform lineages appear to have originated around the end of the Cretaceous. Monophyletic or not, they appear to belong to a close-knit group of "higher waterbirds" which also includes groups such as penguins and Procellariiformes. Quite a lot of fossil bones from around the Cretaceous–Paleogene boundary cannot be firmly placed with any of these orders and rather combine traits of several of them. This is, of course, only to be expected, if the theory that most if not all of these "higher waterbird" lineages originated around that time is correct. Of those apparently basal taxa, the following show some similarities to the traditional Pelecaniformes:

The proposed Elopterygidae—supposedly a family of Cretaceous Pelecaniformes—are neither monophyletic nor does Elopteryx appear to be a modern bird.[10]

References

  1. ^ Jarvis, E.D. et al. (2014) Whole-genome analyses resolve early branches in the tree of life of modern birds. Science, 346(6215):1320-1331. DOI: 10.1126/science.1253451
  2. ^ a b Hedges, S.Blair; Sibley, Charles G (1994). "Molecules vs. morphology in avian evolution: the case of the "pelecaniform" birds". PNAS. 91 (21): 9861–65. doi:10.1073/pnas.91.21.9861. PMC 44917.
  3. ^ Mayr, G. (2007). "Avian higher-level phylogeny: Well-supported clades and what we can learn from a phylogenetic analysis of 2954 morphological characters". Journal of Zoological Systematics and Evolutionary Research. 46: 63–72. doi:10.1111/j.1439-0469.2007.00433.x.
  4. ^ Mikhailov, Konstantin E. (1995). "Eggshell structure in the shoebill and pelecaniform birds: comparison with hamerkop, herons, ibises and storks". Canadian Journal of Zoology. 73 (9): 1754–70. doi:10.1139/z95-207.
  5. ^ Cracraft, Joel; Barker, F. Keith; Braun, Michael J.; Harshman, John; Dyke, Gareth J.; Feinstein, Julie; Stanley, Scott; Cibois, Alice; Schikler, Peter; Beresford, Pamela; García-Moreno, Jaime; Sorenson, Michael D.; Yuri, Tamaki & Mindell, David P. (2004): Phylogenetic Relationships Among Modern Birds (Neornithes): Toward an Avian Tree of Life. In: Cracraft, J. & Donoghue, M.J. (eds.): Assembling the Tree of Life: 468-489. Oxford University Press, New York. ISBN 0-19-517234-5 PDF fulltext
  6. ^ Ericson, P. G. P.; Anderson, C. L.; Britton, T.; Elzanowski, A.; Johansson, U. S.; Källersjö, M.; Ohlson, J. I.; Parsons, T. J.; Zuccon, D.; Mayr, G. (2006). "Diversification of Neoaves: integration of molecular sequence data and fossils". Biology Letters. 2 (4): 543–547. doi:10.1098/rsbl.2006.0523. PMC 1834003. PMID 17148284.
  7. ^ Hackett, Shannon J.; Kimball, Rebecca T.; Reddy, Sushma; Bowie, Rauri C. K.; Braun, Edward L.; Braun, Michael J.; Chojnowski, Jena L.; Cox, W. Andrew; et al. (2008). "A Phylogenomic Study of Birds Reveals Their Evolutionary History". Science. 320 (5884): 1763–68. doi:10.1126/science.1157704. PMID 18583609.
  8. ^ International Ornithological Committee (2 January 2012). "Ibises to Pelicans & Cormorants". IOC World Bird Names: Version 2.11. WorldBirdNames.org. Retrieved 30 April 2012.
  9. ^ Mayr (2003)
  10. ^ Mortimer (2004)

Further reading

  • Bourdon, Estelle; Bouya, Baâdi & Iarochene, Mohamed (2005): Earliest African neornithine bird: A new species of Prophaethontidae (Aves) from the Paleocene of Morocco. J. Vertebr. Paleontol. 25(1): 157–170. DOI: 10.1671/0272-4634(2005)025[0157:EANBAN]2.0.CO;2 HTML abstract
  • Mayr, Gerald (2003): The phylogenetic affinities of the Shoebill (Balaeniceps rex). Journal für Ornithologie 144(2): 157–175. [English with German abstract] HTML abstract
  • Mortimer, Michael (2004): The Theropod Database: Phylogeny of taxa. Retrieved 2013-MAR-02.

External links

Aequornithes

Aequornithes (from Latin aequor, expanse of water + Greek ornithes, birds), or core water birds are defined as "the least inclusive clade containing Gaviidae and Phalacrocoracidae".The monophyly of the group is currently supported by several molecular phylogenetic studies.Aequornithes includes the clades Gaviiformes, Sphenisciformes, Procellariiformes, Ciconiiformes, Suliformes and Pelecaniformes. It does not include several unrelated groups of aquatic birds such as flamingos and grebes (Mirandornithes), shorebirds and auks (Charadriiformes), or the Anseriformes.

Based on a whole-genome analysis of the bird orders, the kagu and sunbittern (Eurypygiformes) and the three species of tropicbirds (Phaethontiformes) together styled as the Eurypygimorphae are the closest sister group of the Aequornithes in the clade Ardeae.

Cladogram based on Burleigh, J.G. et al. (2015)

Antarctic shag

The Antarctic shag (Leucocarbo bransfieldensis), is a marine cormorant native to the South Shetland Islands and the Antarctic peninsula in the South Atlantic Ocean.

Campbell shag

The Campbell shag (Leucocarbo campbelli), also known as the Campbell Island shag, is a species of bird in the family Phalacrocoracidae. It is endemic to Campbell Island. Its natural habitats are open seas and rocky shores. It is a medium-sized bird, around 63 cm in length, with a wingspan of 105 cm, weighing between 1.6 – 2 kg. They only breed on Campbell Island and forage within 10 km of the island.

Some taxonomic authorities, including the International Ornithologists' Union, place this species in the genus Leucocarbo. Others place it in the genus Phalacrocorax.

Eurypygimorphae

Eurypygimorphae is a clade of birds that contains the orders Phaethontiformes (tropicbirds) and Eurypygiformes (kagu and sunbittern) recovered by genome analysis The relationship was first identified in 2013 based on their nuclear genes. Historically these birds were placed at different parts of the tree, with tropicbirds in Pelecaniformes and the kagu and sunbittern in Gruiformes, though in the last decade various genetic analysis had found in the almost obsolete clade Metaves of uncertain placement within that group. Their sister taxon is possibly Aequornithes.

Hamerkop

The hamerkop (Scopus umbretta), is a medium-sized wading bird. It is the only living species in the genus Scopus and the family Scopidae. The species and family was long thought to sit with the Ciconiiformes but is now placed with the Pelecaniformes, and its closest relatives are thought to be the pelicans and shoebill. The shape of its head with a long bill and crest at the back is reminiscent of a hammer, which has given this species its name after the Afrikaans word for hammerhead. It is a medium-sized waterbird with brown plumage. It is found in Africa, Madagascar and Arabia, living in a wide variety of wetlands, including estuaries, lakesides, fish ponds, riverbanks, and rocky coasts. The hamerkop is a sedentary bird that often shows local movements.

The hamerkop takes a wide range of prey, mostly fish and amphibians, but shrimps, insects and rodents are taken too. Prey is usually hunted in shallow water, either by sight or touch, but the species is adaptable and will take any prey it can. The species is renowned for its enormous nests, several of which are built during the breeding season. Unusually for a wading bird the nest has an internal nesting chamber where the eggs are laid. Both parents incubate the eggs, and raise the chicks.

The species is not globally threatened and is locally abundant in Africa and Madagascar, and the International Union for Conservation of Nature (IUCN) has assessed it as being of least concern.

Ixobrychus

Ixobrychus is a genus of bitterns, a group of wading bird in the heron family Ardeidae. Ixobrychus is from Ancient Greek ixias, a reed-like plant and brukhomai, to bellow.It has a single representative species in each of North America, South America, Eurasia, and Australasia. The tropical species are largely resident, but the two northern species are partially migratory, with many birds moving south to warmer areas in winter.

The Ixobrychus bitterns are all small species, with their four larger relatives being in the genus Botaurus. They breed in large reedbeds, and can often be difficult to observe except for occasional flight views due to their secretive behaviour. Like other bitterns, they eat fish, frogs, and similar aquatic life.

Nankeen night heron

The nankeen night heron (Nycticorax caledonicus) also commonly referred to as the rufous night heron, and in Melanesia as melabaob, is a medium-sized heron. It is found in Indonesia, the Philippines, Papua New Guinea, Melanesia, and throughout much of Australia except the arid inland. A small colony has also established near Wanganui, New Zealand.

Phaethontiformes

The Phaethontiformes are an order of birds. They contain one extant family, the tropicbirds (Phaethontidae), and one extinct family Prophaethontidae from the early Cenozoic. Several fossil genera have been described.

The tropicbirds were traditionally grouped in the order Pelecaniformes, which contained the pelicans, cormorants and shags, darters, gannets and boobies and frigatebirds; in the Sibley-Ahlquist taxonomy, the Pelecaniformes were united with other groups into a large "Ciconiiformes". More recently this grouping has been found to be massively paraphyletic (missing closer relatives of its distantly related groups) and split again.

Microscopic analysis of eggshell structure by Konstantin Mikhailov in 1995 found that the eggshells of tropicbirds lacked the covering of thick microglobular material of other Pelecaniformes.Some early studies in the last decade suggested Phaethontiformes were distantly related to Procellariiformes,

but since 2004 they have been placed in Metaves, or in a lineage with no affinities with Procellariiformes, by the results of most recent molecular studies.Jarvis, et al.'s 2014 paper "Whole-genome analyses resolve early branches in the tree of life of modern birds" aligns the Phaethontiformes most closely with the sunbittern and the kagu of the Eurypygiformes, with these two clades forming the sister group of the "core water birds", the Aequornithes, and the Metaves hypothesis abandoned.

Plegadis

Plegadis is a bird genus in the family Threskiornithidae. The genus name derives from Ancient Greek plegados, "sickle", referring to the distinctive shape of the bill. Member species are found on every continent except Antarctica as well as a number of islands. The glossy ibis is easily the most widespread of the three species. Plegadis contains the following three species:

A further two fossil species have been placed in the genus:

Plegadis paganus from the Early Miocene deposits in France; however, it is now placed in Gerandibis pagana.

Plegadis pharangites

Pond heron

Pond herons (Ardeola) are herons, typically 40–50 cm (16–20 in) long with an 80–100 cm (31–39 in) wingspan. Most breed in the tropical Old World, but the migratory squacco heron occurs in southern Europe and the Middle East and winters in Africa. The scientific name comes from Latin ardeola, a small heron (ardea).These pond herons are stocky species with a short neck, short thick bill, typically buff or brownish back, and coloured or streaked fore neck and breast. In summer, adults may have long neck feathers. Ardeola herons are transformed in flight, looking very white due to the brilliant white wings.

Their breeding habitat is marshy wetlands. They nest in small colonies, often with other wading birds, usually on platforms of sticks in trees or shrubs. Two to five eggs are laid.

These herons feed on insects, fish and amphibians. They are often found on small ponds giving rise to the English name shared by most of the species.

Pseudibis

The bird genus Pseudibis consists of two South-East Asian species in the ibis subfamily, Threskiornithinae. The giant ibis is also sometimes placed in this genus.

Genus Pseudibis

The white-shouldered ibis is critically endangered.

Puna ibis

The Puna ibis (Plegadis ridgwayi) is a species of bird in the family Threskiornithidae. It is found in Argentina, Bolivia, Chile, and Peru. Its natural habitats are swamps, marshes and lakes, and most of its range is in the Andean highlands, including the puna, but locally it occurs down to sea level. It has been domesticated by the Uru people for meat and eggs.

Shoebill

The shoebill (Balaeniceps rex) also known as whalehead, whale-headed stork, or shoe-billed stork, is a very large stork-like bird. It derives its name from its enormous shoe-shaped bill. It has a somewhat stork-like overall form and has previously been classified with the storks in the order Ciconiiformes based on this morphology. However, genetic evidence places it with the Pelecaniformes. The adult is mainly grey while the juveniles are browner. It lives in tropical east Africa in large swamps from Sudan to Zambia.

Stripe-backed bittern

The stripe-backed bittern (Ixobrychus involucris) is a species of heron in the family Ardeidae which is found in South America and Trinidad.

Suliformes

The order Suliformes (dubbed "Phalacrocoraciformes" by Christidis & Boles 2008) is an order recognised by the International Ornithologist's Union. In regard to the recent evidence that the traditional Pelecaniformes is polyphyletic, it has been suggested that the group be split up to reflect the true evolutionary relationships. The Suliformes are the oldest order of living birds, with the fossil record of 90 million years ago

Theristicus

Theristicus is a genus of birds in the family Threskiornithidae. They are found in open, grassy habitats in South America. All have a long, decurved dark bill, relatively short reddish legs that do not extend beyond the tail in flight (unlike e.g. Eudocimus and Plegadis), and at least the back is grey.

Tropicbird

Tropicbirds are a family, Phaethontidae, of tropical pelagic seabirds. They are the sole living representatives of the order Phaethontiformes. For many years they were considered part of the Pelecaniformes, but genetics indicates they are most closely related to the Eurypygiformes. There are three species in one genus, Phaethon. The scientific names are derived from Ancient Greek phaethon, "sun". They have predominantly white plumage with elongated tail feathers and small feeble legs and feet.

White-crested tiger heron

The white-crested tiger heron (Tigriornis leucolopha), also known as the white-crested bittern, is a species of heron in the family Ardeidae. It is in the monotypic genus Tigriornis. It is found in Angola, Benin, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mauritania, Nigeria, Senegal, Sierra Leone, and Togo.

Order: Pelecaniformes
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