Editing Bird (section)

====Social systems====
[[File:Raggiana Bird-of-Paradise wild 5.jpg|thumb|alt= Bird faces up with green face, black breast and pink lower body. Elaborate long feathers on the wings and tail.|right|Like others of its family, the male [[Raggiana bird-of-paradise]] has elaborate breeding plumage used to impress females.<ref>{{Cite journal|doi=10.1071/MU9810193|last=Frith|first=C. B.|title=Displays of Count Raggi's Bird-of-Paradise ''Paradisaea raggiana'' and congeneric species |journal=Emu|volume=81|issue=4|pages=193–201| url=http://www.publish.csiro.au/paper/MU9810193.htm|year=1981|bibcode=1981EmuAO..81..193F }}</ref>]]
95 per cent of bird species are socially monogamous. These species pair for at least the length of the breeding season or—in some cases—for several years or until the death of one mate.<ref>{{Cite journal |last=Freed|first=Leonard A.|year=1987|title=The Long-Term Pair Bond of Tropical House Wrens: Advantage or Constraint?|journal=[[The American Naturalist]]|volume=130|issue=4|pages=507–525|doi=10.1086/284728|bibcode=1987ANat..130..507F }}</ref> Monogamy allows for both [[paternal care]] and [[Parental investment|biparental care]], which is especially important for species in which care from both the female and the male parent is required in order to successfully rear a brood.<ref>{{Cite journal|last=Gowaty|first=Patricia A.|title=Male Parental Care and Apparent Monogamy among Eastern Bluebirds (''Sialia sialis'')|journal=[[The American Naturalist]]|volume=121|issue=2|pages=149–160 |year=1983|doi=10.1086/284047|bibcode=1983ANat..121..149G }}</ref> Among many socially monogamous species, [[extra-pair copulation]] (infidelity) is common.<ref>{{Cite journal|last1=Westneat|first1=David F.|year=2003|title=Extra-pair paternity in birds: Causes, correlates, and conflict|doi=10.1146/annurev.ecolsys.34.011802.132439|journal=[[Annual Review of Ecology, Evolution, and Systematics]]|volume=34|pages=365–396|last2=Stewart|first2=Ian R.K.}}</ref> Such behaviour typically occurs between dominant males and females paired with subordinate males, but may also be the result of [[forced copulation]] in ducks and other [[anatidae|anatids]].<ref>{{Cite journal|last1=Gowaty|first1=Patricia A. |last2=Buschhaus|first2=Nancy|year=1998|title=Ultimate causation of aggressive and forced copulation in birds: Female resistance, the CODE hypothesis, and social monogamy|journal=[[American Zoologist]]|volume=38|issue=1|pages=207–225|doi=10.1093/icb/38.1.207|doi-access=free}}</ref>

For females, possible benefits of extra-pair copulation include getting better genes for her offspring and insuring against the possibility of infertility in her mate.<ref>{{Cite journal|last=Sheldon|first=B|year=1994|title=Male Phenotype, Fertility, and the Pursuit of Extra-Pair Copulations by Female Birds|journal=[[Proceedings of the Royal Society B]]|volume=257|issue=1348|pages=25–30|doi=10.1098/rspb.1994.0089|bibcode=1994RSPSB.257...25S }}</ref> Males of species that engage in extra-pair copulations will closely guard their mates to ensure the parentage of the offspring that they raise.<ref>{{Cite journal|last1=Wei|first1=G|year=2005 |title=Copulations and mate guarding of the Chinese Egret |doi=10.1675/1524-4695(2005)28[527:CAMGOT]2.0.CO;2|journal=Waterbirds|volume=28|issue=4|pages=527–530|last2=Zuo-Hua|first2=Yin|last3=Fu-Min|first3=Lei }}</ref>

Other mating systems, including [[Polygyny in animals|polygyny]], [[Polyandry in animals|polyandry]], [[Animal sexual behaviour#Polygamy|polygamy]], [[polygynandry]], and [[Promiscuity#Other animals|promiscuity]], also occur.<ref name = "Gill"/> Polygamous breeding systems arise when females are able to raise broods without the help of males.<ref name = "Gill"/> Mating systems vary across bird families<ref>{{Cite journal |last1=Owens |first1=Ian P. F. |last2=Bennett |first2=Peter M. |date=1997 |title=Variation in mating system among birds: ecological basis revealed by hierarchical comparative analysis of mate desertion |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |language=en |volume=264 |issue=1385 |pages=1103–1110 |doi=10.1098/rspb.1997.0152 |pmc=1688567}}</ref> but variations within species are thought to be driven by environmental conditions.<ref>{{Cite journal |last1=Petrie |first1=Marion |last2=Kempenaers |first2=Bart |date=1998 |title=Extra-pair paternity in birds: explaining variation between species and populations |journal=Trends in Ecology & Evolution |language=en |volume=13 |issue=2 |pages=52–58 |doi=10.1016/S0169-5347(97)01232-9|pmid=21238200 |bibcode=1998TEcoE..13...52P }}</ref> A unique system is the formation of trios where a third individual is allowed by a breeding pair temporarily into the territory to assist with brood raising thereby leading to higher fitness.<ref>{{Cite journal |last1=Barve |first1=Sahas |last2=Riehl |first2=C. |last3=Walters |first3=E. L. |last4=Haydock |first4=J. |last5=Dugdale |first5=H. L. |last6=Koenig |first6=W. D. |date=2021 |title=Lifetime Reproductive Benefits of Cooperative Polygamy Vary for Males and Females in the Acorn Woodpecker (Melanerpes formicivorus). |journal=Proceedings of the Royal Society B: Biological Sciences |volume=208 |issue=1957 |pages=20210579|doi=10.1098/rspb.2021.0579 |pmid=34403633 |pmc=8370801 }}</ref><ref name=":0">{{Cite journal |last1=Roy |first1=Suhridam |last2=Kittur |first2=Swati |last3=Sundar |first3=K. S. Gopi |date=2022 |title=Sarus crane Antigone antigone trios and their triets: Discovery of a novel social unit in cranes |journal=Ecology |volume=103 |issue=6 |pages=e3707 |doi=10.1002/ecy.3707 |pmid=35357696 |bibcode=2022Ecol..103E3707R }}</ref>

Breeding usually involves some form of courtship display, typically performed by the male.<ref>{{Cite book|last=Short|first=Lester L.|year=1993|title=Birds of the World and their Behavior|publisher=Henry Holt and Co|location=New York|isbn=0-8050-1952-9|url=https://archive.org/details/livesofbirdsbird00shor}}</ref> Most displays are rather simple and involve some type of [[bird vocalization|song]]. Some displays, however, are quite elaborate. Depending on the species, these may include wing or tail drumming, dancing, aerial flights, or communal [[Lek mating|lekking]]. Females are generally the ones that drive partner selection,<ref>{{Cite book|last=Burton|first=R|year=1985 |title=Bird Behavior|publisher=Alfred A. Knopf, Inc|isbn=0-394-53957-5|url=https://archive.org/details/birdbehavior0000burt}}</ref> although in the polyandrous [[phalaropes]], this is reversed: plainer males choose brightly coloured females.<ref>{{Cite journal|last1=Schamel|first1=D|year=2004|title=Mate guarding, copulation strategies and paternity in the sex-role reversed, socially polyandrous red-necked phalarope ''Phalaropus lobatus'' |journal=Behavioral Ecology and Sociobiology|volume=57|issue=2|pages=110–118|doi=10.1007/s00265-004-0825-2|last2=Tracy |first2=Diane M.|last3=Lank|first3=David B.|last4=Westneat|first4=David F.|bibcode=2004BEcoS..57..110S }}</ref> [[Courtship feeding]], [[Billing (birds)|billing]] and {{Birdgloss|allopreening}} are commonly performed between partners, generally after the birds have paired and mated.<ref>{{Cite book |last=Attenborough |first=David |author-link=David Attenborough |year=1998 |title=The Life of Birds |location=Princeton |publisher=Princeton University Press |isbn=0-691-01633-X |title-link=The Life of Birds }}</ref>

[[Homosexuality in animals#Birds|Homosexual behaviour has been observed]] in males or females in numerous species of birds, including copulation, pair-bonding, and joint parenting of chicks.<ref>{{cite book |last1=Bagemihl |first1=Bruce |title=Biological exuberance: Animal homosexuality and natural diversity |location=New York |publisher=St. Martin's |year=1999 |pages=479–655}}</ref> Over 130 avian species around the world engage in sexual interactions between the same sex or homosexual behaviours. "Same-sex courtship activities may involve elaborate displays, synchronised dances, gift-giving ceremonies, or behaviours at specific display areas including bowers, arenas, or leks."<ref>{{cite journal |last1=MacFarlane |first1=Geoff R. |last2=Blomberg |first2=Simon P. |last3=Kaplan |first3=Gisela |last4=Rogers |first4=Lesley J. |title=Same-sex sexual behavior in birds: expression is related to social mating system and state of development at hatching |journal=Behavioral Ecology |date=January 2007 |volume=18 |issue=1 |pages=21–33 |doi=10.1093/beheco/arl065 |hdl=10.1093/beheco/arl065 |hdl-access=free }}</ref>