View source for Pelecaniformes

{{Short description|Order of birds}}
{{Automatic taxobox
|taxon = Pelecaniformes 
|fossil_range = Late [[Eocene]]–Holocene, {{fossil range|37.17|earliest=70|0|ref=<ref>{{cite journal| last1= Mayr| first1= G. | first2=V. L. | last2= De Pietri | first3= R. P. | last3= Scofield | first4= T. | last4= Smith | year= 2018| title= A fossil heron from the early Oligocene of Belgium: the earliest temporally well-constrained record of the Ardeidae| journal= [[Ibis (journal)|Ibis]]| volume= 161| number= 1| pages= 79–90 | doi= 10.1111/ibi.12600}}</ref>}}

<small>Possible an early origin based on [[molecular clock]]<ref name= Kuhletal2020>{{cite journal | first1 = H. | last1 = Kuhl | first2 = C. | last2 = Frankl-Vilches | first3 = A. | last3 = Bakker | first4 = G. | last4 = Mayr | first5 = G. | last5 = Nikolaus | first6 = S. T. | last6 = Boerno | first7 = S. | last7 = Klages | first8 = B. | last8 = Timmermann | first9 = M. | last9 = Gahr | year = 2020 | title = An unbiased molecular approach using 3'UTRs resolves the avian family-level tree of life. | journal = [[Molecular Biology and Evolution]] | display-authors= 3| volume = 38 | pages = 108–127 | doi = 10.1093/molbev/msaa191 | pmid = 32781465 | pmc = 7783168 | doi-access = free }}</ref></small>
|image = Pelecaniformes-01.jpg
|image_caption = 
|authority = [[Richard Bowdler Sharpe|Sharpe]], 1891
|subdivision_ranks = Suborder and Families
|subdivision = 
*[[Threskiornithidae]]
*[[Ardeidae]]
*[[Pelecani]]
**[[Scopidae]]
**[[Balaenicipitidae]]
**[[Pelecanidae]]
}}

The '''Pelecaniformes''' {{IPAc-en|p|ɛ|l|ᵻ|ˈ|k|æ|n|ᵻ|f|ɔr|m|iː|z}} are an [[order (biology)|order]] of medium-sized and large [[Water bird|waterbird]]s found [[Cosmopolitan distribution|worldwide]]. As traditionally (but [[wikt:erroneously|erroneously]]) defined, they encompass all birds that have feet with all four [[Webbed foot|toes webbed]]. Hence, they were formerly also known by such names as '''totipalmates''' or '''steganopods'''. Under this obsolete definition, the [[Fregatidae]] (frigatebirds), [[Sulidae]] (gannets and boobies), [[Phalacrocoracidae]] (cormorants and shags), [[Anhingidae]] (darters), and [[Phaethontidae]] (tropicbirds) were included in the Pelecaniformes. Subsequent [[Molecular analysis|molecular]] and [[Morphology (biology)|morphological studies]] indicate they are in fact not close relatives to "true" Pelecaniformes, and they are now placed in their own orders, [[Suliformes]] and [[Phaethontiformes]], respectively. 

Pelecaniformes as currently defined comprise the pelicans, shoebill and hamerkop, which form a [[clade]] within the order (suborder [[Pelecani]]), along with herons ([[Ardeidae]]) and ibises and spoonbills ([[Threskiornithidae]]); the relationships between Pelecani and the other two families are still being debated by [[taxonomist]]s.<ref name="Jarvis">{{cite journal | doi=10.1126/science.1253451 | title=Whole-genome analyses resolve early branches in the tree of life of modern birds | year=2014 | last1=Jarvis | first1=Erich D. | last2=Mirarab | first2=Siavash | last3=Aberer | first3=Andre J. | last4=Li | first4=Bo | last5=Houde | first5=Peter | last6=Li | first6=Cai | last7=Ho | first7=Simon Y. W. | last8=Faircloth | first8=Brant C. | last9=Nabholz | first9=Benoit | last10=Howard | first10=Jason T. | last11=Suh | first11=Alexander | last12=Weber | first12=Claudia C. | last13=Da Fonseca | first13=Rute R. | last14=Li | first14=Jianwen | last15=Zhang | first15=Fang | last16=Li | first16=Hui | last17=Zhou | first17=Long | last18=Narula | first18=Nitish | last19=Liu | first19=Liang | last20=Ganapathy | first20=Ganesh | last21=Boussau | first21=Bastien | last22=Bayzid | first22=Md. Shamsuzzoha | last23=Zavidovych | first23=Volodymyr | last24=Subramanian | first24=Sankar | last25=Gabaldón | first25=Toni | last26=Capella-Gutiérrez | first26=Salvador | last27=Huerta-Cepas | first27=Jaime | last28=Rekepalli | first28=Bhanu | last29=Munch | first29=Kasper | last30=Schierup | first30=Mikkel | journal=Science | volume=346 | issue=6215 | pages=1320–1331 | pmid=25504713 | pmc=4405904 | bibcode=2014Sci...346.1320J | hdl=10072/67425 | display-authors=1 }}</ref>

Most have a bare throat patch ([[gular skin]]), and the [[nostril]]s have evolved into dysfunctional slits, forcing them to breathe through their mouths. They also have a [[wikt:pectinate|pectinate]] ([[comb]]-like) nail on their longest toe, which is used [[Self-grooming|to brush out and separate]] their feathers. They feed on fish, [[squid]], and other [[aquatic animal]]s. Nesting is [[Bird colony|colonial]], but the individual birds are [[Monogamy in animals|monogamous]], pairing up to rear their respective [[Clutch (eggs)|clutch]]es. These birds lack a [[brood patch]]. The young are [[altricial]], hatching from the egg helpless and naked in most species.{{Verify source|date=April 2025|reason=Does this apply to the new definition of Pelecaniformes? I don't think it does, but i'm no birder}}

==Systematics and evolution==
Classically, bird relationships were based solely on [[Morphology (biology)|morphological characteristics]]. The Pelecaniformes were traditionally, but [[wikt:erroneously|erroneously]], defined as birds that have feet with all four [[webbed foot|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 [[frigatebird]]s, [[gannet]]s, [[cormorant]]s, [[anhinga]]s, and [[tropicbird]]s.<ref name="Hedges94">{{cite journal| author1=Hedges, S. Blair |author2=Sibley, Charles G. |year=1994|title=Molecules vs. morphology in avian evolution: the case of the "pelecaniform" birds|journal=PNAS|volume=91|issue=21|pages=9861–65|doi=10.1073/pnas.91.21.9861|pmid= 7937906 |pmc= 44917|bibcode= 1994PNAS...91.9861H |doi-access=free }}</ref>

Research from the beginning of the 21st century strongly suggested that the similarities between this traditional definition of Pelecaniformes are the result of [[convergent evolution]] rather than [[common descent]], being adaptations that were converged upon by birds living in and near aquatic environments; the traditional definition of the group would thus be [[polyphyletic]].<ref>{{cite journal| last= Mayr| first= Gerald | year=2003| title=The phylogenetic affinities of the Shoebill (''Balaeniceps rex'')| journal= Journal für Ornithologie| volume= 144| number=2| pages= 157–175| doi= 10.1007/BF02465644 | bibcode= 2003JOrni.144..157M | url= https://www.senckenberg.de/wp-content/uploads/2019/09/balaeniceps.pdf| via= senckenberg.de}}</ref> 

[[Charles Sibley|Sibley]] and Ahlquist's landmark [[DNA–DNA hybridisation]] studies (now known as the [[Sibley–Ahlquist taxonomy of birds|Sibley–Ahlquist taxonomy]]) led to them placing the families traditionally contained within the Pelecaniformes together with the [[grebe]]s, [[cormorant]]s, [[Threskiornithidae|ibises and spoonbills]], [[New World vulture]]s, [[stork]]s, penguins, [[albatross]]es, [[petrel]]s, and [[loon]]s 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 had 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.<ref name= Mayr46>{{Cite journal | last1 = Mayr | first1 = G. | title = Avian higher-level phylogeny: Well-supported clades and what we can learn from a phylogenetic analysis of 2954 morphological characters | doi = 10.1111/j.1439-0469.2007.00433.x | journal = Journal of Zoological Systematics and Evolutionary Research | volume = 46| pages = 63–72 | year = 2007 | s2cid = 59486699 | doi-access = free }}</ref> Mounting evidence pointed to the [[shoebill]] as a close relative of pelicans.<ref name="Hedges94"/>{{Needs update|date=April 2025|reason=There's surely a more recent review of this clade by now}} This also included [[microscopic analysis]] of [[eggshell]] structure by Konstantin Mikhailov in 1995, who found that the shells of pelecaniform eggs were covered in a thick microglobular material; importantly, the eggs of shoebills have these strucures, but not those of the tropicbirds.<ref>{{cite journal |last=Mikhailov |first=Konstantin E. |title=Eggshell structure in the shoebill and pelecaniform birds: comparison with hamerkop, herons, ibises and storks |journal=Canadian Journal of Zoology |year= 1995 |issue=9 |volume=73 |pages=1754–70 |doi=10.1139/z95-207|bibcode=1995CaJZ...73.1754M }}</ref> Reviewing genetic evidence to date, Cracraft and colleagues surmised that pelicans were sister to the shoebill with the hamerkop as the next earlier offshoot.<ref>{{aut|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:'' {{aut|Cracraft, J. & Donoghue, M.J. (eds.)}}: ''Assembling the Tree of Life'': 468–489. Oxford University Press, New York. {{ISBN|0-19-517234-5}} [http://si-pddr.si.edu/dspace/bitstream/10088/6267/1/2004_Cracraft_et_al.pdf PDF fulltext] {{Webarchive|url=https://web.archive.org/web/20130514174500/http://si-pddr.si.edu/dspace/bitstream/10088/6267/1/2004_Cracraft_et_al.pdf |date=2013-05-14 }}</ref> Ericson and colleagues sampled five [[nuclear gene]]s in a 2006 study spanning the breadth of bird lineages, and came up with pelicans, shoebill and hamerkop in a clade.<ref>{{Cite journal | last1 = Ericson | first1 = P. G. P. | last2 = Anderson | first2 = C. L. | last3 = Britton | first3 = T.| last4 = Elzanowski | first4 = A. | last5 = Johansson | first5 = U. S. | last6 = Källersjö | first6 = M. | last7 = Ohlson | first7 = J. I. | last8 = Parsons | first8 = T. J. | last9 = Zuccon | first9 = D. | doi = 10.1098/rsbl.2006.0523 | last10 = Mayr | first10 = G. | display-authors= 3| title = Diversification of Neoaves: integration of molecular sequence data and fossils | journal = Biology Letters | volume = 2 | issue = 4 | pages = 543–547 | year = 2006 | pmid =  17148284| pmc =1834003 }}</ref> 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 the heron and ibis group a sister to the pelican/shoebill/hamerkop clade.<ref name=Hackett>{{cite journal | year = 2008 | title = A Phylogenomic Study of Birds Reveals Their Evolutionary History | journal = Science | volume = 320 | pages = 1763–68 | doi = 10.1126/science.1157704 | display-authors= 3| pmid = 18583609 
| first1 = Shannon J. | last1 = Hackett
| first2 = Rebecca T. | last2 = Kimball
| first3 = Sushma | last3 = Reddy
| first4 = Rauri C. K. | last4 = Bowie
| first5 = Edward L. | last5 = Braun
| first6 = Michael J. | last6 = Braun
| first7 = Jena L. | last7 = Chojnowski
| first8 = W. Andrew | last8 = Cox
| first9 = Kin-Lan | last9 = Han
| first10 = John | last10 = Harshman
| first11 = Christopher J. | last11 = Huddleston
| first12 = Ben D. | last12 = Marks
| first13 = Kathleen J. | last13 = Miglia
| first14 = William S. | last14 = Moore
| first15 = Frederick H. | last15 = Sheldon
| first16 = David W. | last16 = Steadman
| first17 = Christopher C. | last17 = Witt
| first18 = Tamaki | last18 = Yuri
| issue = 5884 | bibcode = 2008Sci...320.1763H | s2cid = 6472805 }}</ref> The phylogenetic tree below illustrates this situation:

{{clade|style=font-size:100%
|label1='''Pelecaniformes'''
|1={{Clade
   |label1=[[Ardei]]
   |1={{Clade
     |1=[[Threskiornithidae]] – ibises, spoonbills (36 species)
     |2=[[Ardeidae]] – herons, bitterns (72 species) }}
   |label2=[[Pelecani]]
   |2={{Clade
      |1=[[Pelican|Pelecanidae]]  – pelicans (8 species)
      |2={{Clade
         |1=[[Hamerkop|Scopidae]] – hamerkop
         |2=[[Shoebill|Balaenicipitidae]] – shoebill }} }} }} }}

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]]). The IOC considers Threskiornithidae and Ardeidae to from a clade, citing Hackett et al. 2008.<ref name=Hackett /><ref>{{cite web|url=http://www.worldbirdnames.org/n-ibises.html|date=2 January 2012|access-date=30 April 2012|title=Ibises to Pelicans & Cormorants|author=International Ornithological Committee|work=IOC World Bird Names: Version 2.11|publisher= WorldBirdNames.org|archive-date=1 March 2012|archive-url=https://web.archive.org/web/20120301235841/http://www.worldbirdnames.org/n-ibises.html|url-status=dead}}</ref>

Another hypothesis is that Threskiornithidae is sister to the rest of Pelecaniformes, and Ardeidae and Pelecani form a clade,<ref>{{Cite journal | last1= Reddy | first1=S. | last2=Kimball | first2=R.T. | last3=Pandey | first3=A. | last4=Hosner | first4=P.A. | last5=Braun | first5=M.J. | last6=Hackett | first6=S.J. | last7=Han | first7=K.-L. | last8=Harshman | first8=J. | last9=Huddleston | first9=C.J. | last10=Kingston | first10=S. | last11=Marks | first11=B.D. | last12=Miglia | first12=K.J. | last13=Moore | first13=W.S. | last14= Sheldon | first14=F.H. | last15=Witt | first15=C.C. | last16=Yuri | first16=T. | last17=Braun | first17=E.L. | display-authors= 3| year=2017 | title=Why do phylogenomic data sets yield conflicting trees? Data type influences the avian tree of life more than taxon sampling | journal= [[Systematic Biology]] | volume=66 | issue=5 | pages=857–879 | doi=10.1093/sysbio/syx041 | pmid=28369655 | doi-access=free }}</ref><ref>{{Cite journal | last1=Kuhl | first1=H. | last2=Frankl-Vilches | first2=C. | last3=Bakker | first3=A. | last4=Mayr | first4=G. | last5=Nikolaus | first5=G. | last6=Boerno | first6=S.T. | last7=Klages | first7=S. | last8= Timmermann | first8=B. | last9=Gahr | first9=M. | display-authors= 3| year=2021 | title=An unbiased molecular approach using 3′-UTRs resolves the avian family-level tree of life | journal=Molecular Biology and Evolution | volume=38 | issue=1 | pages=108–127 | doi=10.1093/molbev/msaa191 | pmid=32781465 | pmc= 7783168 | doi-access=free }}</ref> as can be seen below:

{{clade|style=font-size:100%
|label1='''Pelecaniformes'''
|1={{Clade
   |1=[[Threskiornithidae]] – ibises, spoonbills (36 species)
   |2={{Clade
      |1=[[Ardeidae]] – herons, bitterns (72 species)
      |label2=[[Pelecani]]
      |2={{Clade
         |1=[[Pelican|Pelecanidae]]  – pelicans (8 species)
         |2={{Clade
            |1=[[Hamerkop|Scopidae]] – hamerkop
            |2=[[Shoebill|Balaenicipitidae]] – shoebill }} }} }} }} }}


These controversies have been explained by analyses of rare genomic changes, which suggested that after the divergence of the pelican (Pelecanidae), heron (Ardeidae), and ibis (Threskiornithidae) lineages, interspecies hybridization led to gene flow causing the heron lineage to exhibit genetic signatures indicating affinity to both the pelican and ibis lineages.<ref>{{Cite journal | last1= Kuramoto | first1= T. | last2= Nishihara | first2= H. | last3= Watanabe | first3= M. | last4= Okada | first4= N. | year=2015 | title= Determining the Position of Storks on the Phylogenetic Tree of Waterbirds by Retroposon Insertion Analysis | journal= [[Genome Biology and Evolution]] | volume=7 | issue=12 | pages=3180–3189 | doi=10.1093/gbe/evv213 | pmid=26527652 | doi-access=free }}</ref>

===Fossils===
All families in the traditional Pelecaniformes (except the Phalacrocoracidae) have only a few handfuls of [[extant species]] at most, but many were more speciose in the Early [[Neogene]]. The pelecaniform lineages appear to have originated around the end of the [[Cretaceous]], appearing 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 (evolution)|basal]] [[taxa]], the following show some similarities to the traditional Pelecaniformes:

*{{extinct}} ''[[Lonchodytes]]'' (Lance Creek Late Cretaceous of Wyoming, US)
*{{extinct}} ''[[Torotix]]'' (Late Cretaceous)
*{{extinct}} ''[[Tytthostonyx]]'' (Late Cretaceous/Early Palaeocene)
*{{extinct}} ''[[Cladornis]]'' (Deseado Early Oligocene of Patagonia, Argentina)<!-- Evolution38:1384 -->
*{{extinct}} ''"[[Liptornis]]"''—a ''[[nomen dubium]]''<!-- Evolution38:1384; 39:1174 -->

Fossil genera and species are discussed in the respective family or genus accounts; one little-known prehistoric Pelecaniforme, however, cannot be classified accurately enough to assign them to a family; ''"Sula" ronzoni''<!-- AnnNHMusWien104A:237 --> from Early [[Oligocene]] rocks at [[Ronzon]], France, which was initially believed to be a [[Mergus|sea-duck]], is a possible ancestral Pelecaniform. The proposed [[Elopterygidae]]—supposedly a family of Cretaceous Pelecaniformes—are neither [[monophyletic]] nor does ''Elopteryx'' appear to be a modern bird.<ref> {{cite web| last=Mortimer| first= Michael | year= 2004| publisher=The Theropod Database| website= archosaur.us | url= http://archosaur.us/theropoddatabase/Phylogeny%20of%20Taxa.html | archiveurl= https://web.archive.org/web/20130516175802/http://archosaur.us/theropoddatabase/Phylogeny%20of%20Taxa.html | title= Phylogeny of taxa| archivedate= 2013-05-16 |accessdate= }}</ref>

== References ==
{{Reflist}}

==Further reading==<!-- Auk64:65. SystematicBiology54:620. -->
* Bourdon, Estelle; Bouya, Baâdi & Iarochene, Mohamed (2005): Earliest African neornithine bird: A new species of Prophaethontidae (Aves) from the Paleocene of Morocco. ''[[Society of Vertebrate Paleontology|J. Vertebr. Paleontol.]]'' '''25'''(1): 157–170. [[Digital Object Identifier|DOI]]: 10.1671/0272-4634(2005)025[0157:EANBAN]2.0.CO;2 [http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634(2005)025%5B0157%3AEANBAN%5D2.0.CO%3B2 HTML abstract]

==External links==
{{Commons and category|Pelecaniformes|Pelecaniformes}}
{{Wikispecies|Pelecaniformes}}

* [http://tolweb.org/Pelecaniformes/57152 Tree of Life: Pelecaniformes]

{{Pelecaniformes}}
{{Birds}}
{{Taxonbar|from=Q19338}}
{{Authority control}}

[[Category:Pelecaniformes| ]]
[[Category:Seabirds]]
[[Category:Bird orders]]
[[Category:Extant Paleogene first appearances]]
[[Category:Taxa named by Richard Bowdler Sharpe]]