View source for Ornithology

==History==
{{For timeline}}
The history of ornithology largely reflects the trends in the [[history of biology]], as well as many other scientific disciplines, including [[ecology]], [[anatomy]], [[physiology]], [[paleontology]], and more recently, molecular biology. Trends include the move from mere descriptions to the identification of patterns, thus towards elucidating the processes that produce these patterns. Since its modern views through scientific consensus of ornithology in the 21st century, birds are specifically descendants of small, feathered, maniraptoran theropods, which emerged from dinosaurs from the [[Jurassic]] period, 160 million years ago.<ref>{{cite journal | last1=Field | first1=Daniel J. | last2=Burton | first2=M. Grace | last3=Benito | first3=Juan | last4=Plateau | first4=Olivia | last5=Navalón | first5=Guillermo | title=Whence the birds: 200 years of dinosaurs, avian antecedents | journal=Biology Letters | date=2025 | volume=21 | issue=1 | article-number=20240500 | doi=10.1098/rsbl.2024.0500 | pmid=39837495 | pmc=11750382 }}</ref>

===Early knowledge and study===
Humans have had an observational relationship with birds since [[prehistory]], with some stone-age drawings being amongst the oldest indications of an interest in birds.<ref name="Gurney, JH 1921">{{Cite journal |author=Gurney, JH |year=1921|url=https://archive.org/details/cu31924005489558 |title=Early annals of ornithology |journal=Nature|volume=108|issue=2713|pages=268|bibcode=1921Natur.108..268.|doi=10.1038/108268a0|hdl=2027/coo.31924090299532|s2cid=4033666|hdl-access=free}}</ref><ref>{{cite book|title=Bird books and bird art|author=Anker, Jean|publisher=Springer-Science|year=1979|pages=1–5}}</ref> Birds were perhaps important as food sources, and bones of as many as 80 species have been found in excavations of early [[Stone Age]] settlements.<ref>{{cite journal |author=Nadel, K. D., Ehud Weiss, Orit Simchoni, Alexander Tsatskin, Avinoam Danin, and Mordechai |year=2004 |title=Stone Agehut in Israel yields world's oldest evidence of bedding|journal=Proc. Natl. Acad. Sci. U.S.A. |volume=101 |issue=17 |pages=6821–6826 |url=http://www.pnas.org/cgi/reprint/0308557101v1.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.pnas.org/cgi/reprint/0308557101v1.pdf |archive-date=2022-10-09 |url-status=live |doi=10.1073/pnas.0308557101|pmid=15090648 |pmc=404215|bibcode = 2004PNAS..101.6821N |doi-access=free }}</ref><ref>{{cite book |author=Newton, Alfred |title=Ornithology. Reprinted from Encyclopædia Britannica (9th Ed.) |year=1884|url=https://archive.org/details/ornithology00newt|publisher=[S.l. : s.n. }}</ref><ref>{{cite book |url=https://archive.org/details/dictionaryofbird00newt |title=A Dictionary of Birds |publisher=Adam & Charles Black, London |year=1893–1896 |author=Newton, Alfred}}</ref> [[Water bird]] and [[seabird]] remains have also been found in [[shell mound]]s on the island of [[Oronsay, Colonsay|Oronsay]] off the coast of [[Scotland]].<ref name="Gurney, JH 1921" />
[[File:Facsimile Painting of Geese, Tomb of Nefermaat and Itet MET DT226227.jpg|left|thumb|483x483px|Geese from a wall panel from the tomb of [[Nefermaat]], Egypt {{Circa|2575}}–2551 BC]]
Cultures around the world have rich vocabularies related to birds.<ref>{{cite web|url=http://www.birdinghawaii.co.uk/Hawaiianbirdnames2.htm|work=birdinghawaii.co.uk/|title=Hawaiian bird names|access-date=11 June 2008|url-status=dead|archive-url=https://web.archive.org/web/20090604150628/http://www.birdinghawaii.co.uk/Hawaiianbirdnames2.htm|archive-date=4 June 2009}}</ref> Traditional bird names are often based on detailed knowledge of the behaviour, with many names being [[onomatopoeic]], and still in use.<ref>{{cite book |author1=Gill, Frank |author2=Wright, M. |name-list-style=amp |year=2006 |title=Birds of the world: Recommended English Names |publisher=Princeton University Press |url=http://www.worldbirdnames.org/principles.html |access-date=2007-12-13 |archive-url=https://web.archive.org/web/20081020045752/http://worldbirdnames.org/principles.html |archive-date=2008-10-20 |url-status=dead }}</ref> Traditional knowledge may also involve the use of birds in folk medicine<ref>{{cite journal |author1=Mahawar, M. M.  |author2=D. P. Jaroli  |name-list-style=amp |year=2007 |title=Traditional knowledge on zootherapeutic uses by the Saharia tribe of Rajasthan, India |journal=Journal of Ethnobiology and Ethnomedicine |volume=3 |page=25|doi=10.1186/1746-4269-3-25 |pmid=17547781 |pmc=1892771 |issue=1 |doi-access=free }}</ref> and knowledge of these practices is passed on through oral traditions (see [[ethnoornithology]]).<ref>{{cite web |url=http://www.cvco.org/science/audubon/Sep2004article.html |author=Shapiro, M. |title=Native bird names |publisher=Richmond Audubon Society |access-date=2007-12-01 |archive-url=https://web.archive.org/web/20070816032023/http://www.cvco.org/science/audubon/Sep2004article.html |archive-date=2007-08-16 |url-status=dead }}</ref><ref>{{cite journal |author=Hohn, E.O. |year=1973|title=Mammal and bird names in the Indian languages of the Lake Athabasca area |journal=Arctic |volume=26 |issue=2|pages=163–171 |url=http://pubs.aina.ucalgary.ca/arctic/Arctic26-2-163.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://pubs.aina.ucalgary.ca/arctic/Arctic26-2-163.pdf |archive-date=2022-10-09 |url-status=live |doi=10.14430/arctic2912}}</ref> Hunting of wild birds as well as their domestication would have required considerable knowledge of their habits. [[Poultry]] farming and [[falconry]] were practised from early times in many parts of the world. Artificial incubation of poultry was practised in China around 246&nbsp;BC and at least around 400&nbsp;BC in Egypt.<ref>{{cite book |author1=Funk, E. M.  |author2=Irwin, M. R.  |name-list-style=amp |year=1955 |title=Hatching Operation and Management |publisher=John Wiley & Sons}}</ref> The Egyptians also made use of birds in their hieroglyphic scripts, many of which, though stylized, are still identifiable to species.<ref>{{cite book|url=https://archive.org/stream/dieantiketierwel02kell#page/n19/mode/2up|title=Die Antike Tierwelt|author=Keller, Otto|publisher=Wilhelm Engelmann|year=1913|volume=2|place=Leipzing|pages=1–43|language=de}}</ref>[[File:BelonBirdSkel.jpg|thumb|Belon's comparison of birds and humans in his ''Book of Birds'', 1555]] Early written records provide valuable information on the past distributions of species. For instance, [[Xenophon]] records the abundance of the [[ostrich]] in [[Assyria]] (Anabasis, i. 5); this subspecies from Asia Minor is extinct and all extant ostrich races are today restricted to [[Africa]]. Other old writings such as the [[Vedas]] (1500–800 BC) demonstrate the careful observation of avian life histories and include the earliest reference to the habit of [[brood parasite|brood parasitism]] by the [[Asian koel]] (''Eudynamys scolopaceus'').<ref>{{cite journal |author=Ali, S. |year=1979 |title=Bird study in India: its history and its importance |jstor=23001825|journal=India International Centre Quarterly|volume=6|issue=2 |pages=127–139}}</ref> Like writing, the early art of China, Japan, Persia, and India also demonstrates knowledge, with examples of scientifically accurate bird illustrations.<ref>Lack, David (1965) Enjoying Ornithology. Taylor & Francis. pp. 175–176.</ref>

[[Aristotle]] in 350&nbsp;BC in his ''[[History of animals]]''<ref>{{cite book |author=Aristotle |url=http://classics.mit.edu/Aristotle/history_anim.6.vi.html |title=Historia Animalium|trans-title=The History of Animals|translator=D'Arcy Wentworth Thompson}}</ref> noted the habits of [[bird migration]], moulting, egg laying, and lifespans, as well as compiling a list of 170 different bird species. However, he also introduced and propagated several myths, such as the idea that [[swallow]]s [[hibernated]] in winter, although he noted that [[common crane|cranes]] migrated from the steppes of [[Scythia]] to the marshes at the headwaters of the [[Nile]]. The idea of swallow hibernation became so well established that even as late as in 1878, [[Elliott Coues]] could list as many as 182 contemporary publications dealing with the hibernation of swallows and little published evidence to contradict the theory.<ref>{{cite report |author-last1=Lincoln |author-first1= Frederick C. |author-last2= Peterson |author-first2= Steven R. |author-last3=Zimmerman |author-first3= John L.  |year=1998 |title=Migration of birds |publisher=U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, D.C. Circular 16. Jamestown, ND: Northern Prairie Wildlife Research Center Online. |url=https://www.npwrc.usgs.gov/resource/birds/migratio/index.htm |url-status=dead |archive-url=https://web.archive.org/web/20070518031657/http://www.npwrc.usgs.gov/resource/birds/migratio/index.htm |archive-date=2007-05-18 }}</ref><ref>{{cite journal |author=Allen, JA |year=1909 |title=Biographical memoir of Elliott Coues |journal=National Academy of Sciences Biographical Memoirs |volume=6 |pages=395–446|url=http://books.nap.edu/html/biomems/ecoues.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://books.nap.edu/html/biomems/ecoues.pdf |archive-date=2022-10-09 |url-status=live}}</ref> Similar misconceptions existed regarding the breeding of [[barnacle geese]]. Their nests had not been seen, and they were believed to grow by transformations of [[goose barnacles]], an idea that became prevalent from around the 11th century and noted by Bishop Giraldus Cambrensis ([[Gerald of Wales]]) in ''[[Topographia Hiberniae]]'' (1187).<ref>{{cite journal |author=Payne, S. |year=1929 |title=The Myth of the Barnacle Goose |journal=Int. J. Psycho-Anal. |volume=10 |pages=218–227}}</ref> Around 77&nbsp;AD, [[Pliny the Elder]] described birds, among other creatures, in his ''[[Natural History (Pliny)|Historia Naturalis]]''.<ref>{{Cite journal|last=Gudger|first=E. W.|date=1924|title=Pliny's Historia naturalis. The Most Popular Natural History Ever Published|journal=Isis|language=en|volume=6|issue=3|pages=269–281|doi=10.1086/358236|s2cid=144264511|issn=0021-1753}}</ref>

The earliest record of falconry comes from the reign of Sargon II (722–705 BC) in [[Assyria]]. Falconry is thought to have made its entry to Europe only after 400&nbsp;AD, brought in from the east after invasions by the [[Huns]] and [[Alans]]. Starting from the eighth century, numerous Arabic works on the subject and general ornithology were written, as well as translations of the works of ancient writers from Greek and [[Syriac language|Syriac]]. In the 12th and 13th centuries, crusades and conquest had subjugated Islamic territories in southern Italy, central Spain, and the Levant under European rule, and for the first time translations into Latin of the great works of Arabic and Greek scholars were made with the help of Jewish and Muslim scholars, especially in [[Toledo, Spain|Toledo]], which had fallen into Christian hands in 1085 and whose libraries had escaped destruction. [[Michael Scot]]us from Scotland made a Latin translation of Aristotle's work on animals from Arabic here around 1215, which was disseminated widely and was the first time in a millennium that this foundational text on zoology became available to Europeans. Falconry was popular in the [[Normans|Norman]] court in Sicily, and a number of works on the subject were written in [[Palermo]]. [[Frederick II, Holy Roman Emperor|Emperor Frederick II of Hohenstaufen]] (1194–1250) learned about an falconry during his youth in Sicily and later built up a [[menagerie]] and sponsored translations of Arabic texts, among which the popular Arabic work known as the ''[[Moamyn|Liber Moaminus]]'' by an unknown author which was translated into Latin by [[Theodore of Antioch (philosopher)|Theodore of Antioch]] from Syria in 1240–1241 as the ''De Scientia Venandi per Aves'', and also Michael Scotus (who had removed to Palermo) translated [[Avicenna|Ibn Sīnā]]'s ''[[Kitāb al-Hayawān (Aristotle)|Kitāb al-Ḥayawān]]'' of 1027 for the Emperor, a commentary and scientific update of Aristotle's work which was part of Ibn Sīnā's massive ''[[The Book of Healing|Kitāb al-Šifāʾ]]''. Frederick II eventually wrote his own treatise on falconry, the ''[[De arte venandi cum avibus]]'', in which he related his ornithological observations and the results of the hunts and experiments his court enjoyed performing.<ref name="egerton">{{cite journal |author=Egerton, F. |year=2003 |title=A History of the Ecological Sciences, Part 8: Fredrick II of Hohenstaufen: Amateur Avian Ecologist and Behaviorist |journal=Bulletin of the Ecological Society of America |volume=84 |issue=1 |pages=40–44|url=http://esapubs.org/bulletin/current/history_list/history_part8.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://esapubs.org/bulletin/current/history_list/history_part8.pdf |archive-date=2022-10-09 |url-status=live|doi=10.1890/0012-9623(2003)84[40:AHOTES]2.0.CO;2 }}</ref><ref>{{cite journal |last=van Oppenraay |first=Aafke M.I. |date=2017 |title=Avicenna's ''Liber de animalibus'' ('''Abbreviatio Avicennae''') - Preliminaries and State of Affairs |url=https://pure.knaw.nl/ws/files/6003490/Avicenna_s_Liber_de_animalibus_Abbreviatio_Avicennae_._VanOppenraay_2017.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://pure.knaw.nl/ws/files/6003490/Avicenna_s_Liber_de_animalibus_Abbreviatio_Avicennae_._VanOppenraay_2017.pdf |archive-date=2022-10-09 |url-status=live |journal=Documenti e Studi Sulla Tradizione Filosofica Medievale |volume=28 |pages=401–416 |access-date=4 May 2018}}</ref>

Several early German and French scholars compiled old works and conducted new research on birds. These included [[Guillaume Rondelet]], who described his observations in the Mediterranean, and [[Pierre Belon]], who described the fish and birds that he had seen in France and the Levant. Belon's ''Book of Birds'' (1555) is a folio volume with descriptions of some 200 species. His comparison of the skeletons of humans and birds is considered as a landmark in [[comparative anatomy]].<ref name="miall">{{cite book |author=Miall, L. C. |year=1911 |title=History of Biology |publisher=Watts and Co. |url=https://archive.org/details/historyofbiology00mialrich}}</ref> [[Volcher Coiter]] (1534–1576), a Dutch anatomist, made detailed studies of the internal structures of birds and produced a classification of birds, ''De Differentiis Avium'' (around 1572), that was based on structure and habits.<ref name="egallen">{{cite journal |author=Allen, Elsa G. |author-link=Elsa Guerdrum Allen |year=1951 |title=The History of American Ornithology before Audubon |journal=Transactions of the American Philosophical Society |series=New Series |volume=41 |issue=3 |pages=387–591 |doi=10.2307/1005629|jstor=1005629|bibcode=1951TAPS...41..387A |hdl=2027/uc1.31822011760568 |hdl-access=free }}</ref> [[Konrad Gesner]] wrote the ''Vogelbuch'' and ''Icones avium omnium'' around 1557. Like Gesner, [[Ulisse Aldrovandi]], an encyclopedic naturalist, began a 14-volume natural history with three volumes on birds, entitled ''ornithologiae hoc est de avibus historiae libri XII'', which was published from 1599 to 1603. Aldrovandi showed great interest in plants and animals, and his work included 3000 drawings of fruits, flowers, plants, and animals, published in 363 volumes. His ''Ornithology'' alone covers 2000 pages and included such aspects as the [[chicken]] and poultry techniques. He used a number of traits including behaviour, particularly bathing and dusting, to classify bird groups.<ref>{{cite journal| last=Beddall|first=Barbara G.| year=1957| title=Historical notes on avian classification| journal=Systematic Zoology| volume=6| issue=3| pages=129–136| doi=10.2307/2411751|jstor=2411751}}</ref><ref>{{cite book|author=Lind, L. R.|year=1963|title=Aldrovandi on Chickens: The Ornithology of Ulisse Aldrovandi, vol. 2, Bk xiv, translated and edited by L. R. Lind|publisher=University of Oklahoma Press}}</ref><ref>{{cite book |author=Aldrovandi, Ulisse |year=1599 |title=Ornithologiae |url=https://archive.org/details/ARes04102}}</ref>

[[File:AldrovandiOrnithology.jpg|thumb|right|upright|Cover of [[Ulisse Aldrovandi]]'s ''Ornithology'', 1599]]

[[File:ValliDeTodi1601.jpg|thumb|[[Antonio Valli da Todi]], who wrote on [[aviculture]] in 1601, knew the connections between territory and song.<ref>{{cite journal |journal=Archives of Natural History |volume=35 |pages=281–305 |doi=10.3366/E0260954108000399 |title=Bird-keeping and the development of ornithological science |year=2008 |author1=Birkhead TR  |author2=S van Balen  |name-list-style=amp |issue=2}}</ref>]]
[[William Turner (ornithologist)|William Turner]]'s ''Historia Avium'' (''History of Birds''), published at [[Cologne]] in 1544, was an early ornithological work from England. He noted the commonness of [[red kite|kite]]s in English cities where they snatched food out of the hands of children. He included folk beliefs such as those of anglers. Anglers believed that the [[osprey]] emptied their fishponds and would kill them, mixing the flesh of the osprey into their fish bait. Turner's work reflected the violent times in which he lived, and stands in contrast to later works such as [[Gilbert White]]'s 1789 ''[[The Natural History and Antiquities of Selborne]]'' which were written in a tranquil era.<ref name="miall"/><ref name="gilbertwhite">{{cite book |last=White |first=Gilbert |title=The Natural History and Antiquities of Selborne |year= 1887 |orig-year=1789 |location=London |publisher=Cassell & Company| oclc=3423785 |pages=38–39 |url=http://www.gutenberg.org/files/20933/20933-h/20933-h.htm}}</ref>

In the 17th century, [[Francis Willughby]] (1635–1672) and [[John Ray]] (1627–1705) created the first major system of bird classification that was based on function and morphology rather than on form or behaviour. Willughby's ''Ornithologiae libri tres'' (1676) completed by John Ray is sometimes considered to mark the beginning of scientific ornithology. Ray also worked on ''Ornithologia'', which was published posthumously in 1713 as ''Synopsis methodica avium et piscium''.<ref name="white">{{cite web |author=White, Jeanne A. |year=1999 |title=Ornithology Collections in the Libraries at Cornell University: A Descriptive Guide |url=https://rmc.library.cornell.edu/ornithology/guide/hillguide.htm |access-date=2007-12-01}}</ref> The earliest list of British birds, ''Pinax Rerum Naturalium Britannicarum'', was written by [[Christopher Merrett]] in 1667, but authors such as John Ray considered it of little value.<ref>{{cite journal |author=Koinm, Albert J. |year=2000 |title=Christopher Merrett's Use of Experiment |journal=Notes and Records of the Royal Society of London |volume=54 |issue=1 |pages=23–32 |doi=10.1098/rsnr.2000.0093|s2cid=144805851 |doi-access= }}</ref> Ray did, however, value the expertise of the naturalist [[Sir Thomas Browne]] (1605–1682), who not only answered his queries on ornithological identification and nomenclature, but also those of Willoughby and Merrett in letter correspondence. Browne himself in his lifetime kept an eagle, owl, cormorant, bittern, and ostrich, penned a tract on falconry, and introduced the words "incubation" and "oviparous" into the English language.<ref>{{cite book|pages=i–xxv|title=Notes and Letters on the Natural History of Norfolk, more especially on the birds and fishes|author=[[Thomas Browne|Browne, Thomas]] (with notes by [[Thomas Southwell (naturalist)|Thomas Southwell]])|url=https://archive.org/stream/cu31924024779187#page/n5/mode/2up|publisher=Jarrold & Sons|place=London|year=1902}}</ref><ref>{{cite journal|author=Mullens, W.H. |title=Some early British Ornithologists and their works. VII. John Ray (1627-1705) and Francis Willughby (1635-1672)|pages=290–300 |volume=2|issue=9|url=http://britishbirds.co.uk/wp-content/uploads/article_files/V02/V02_N09/V02_N09_P290_300_A047.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://britishbirds.co.uk/wp-content/uploads/article_files/V02/V02_N09/V02_N09_P290_300_A047.pdf |archive-date=2022-10-09 |url-status=live|journal=British Birds|year=1909}}</ref> 
[[File:An Experiment on a Bird in an Air Pump by Joseph Wright of Derby, 1768.jpg|thumb|''[[An Experiment on a Bird in the Air Pump]]'', [[Joseph Wright of Derby]], 1768]]
Towards the late 18th century, [[Mathurin Jacques Brisson]] (1723–1806) and [[Georges-Louis Leclerc, Comte de Buffon|Comte de Buffon]] (1707–1788) began new works on birds. Brisson produced a six-volume work ''Ornithologie'' in 1760 and Buffon's included nine volumes (volumes 16–24) on birds ''Histoire naturelle des oiseaux'' (1770–1785) in his work on science '' [[Histoire Naturelle |Histoire naturelle générale et particulière]]'' (1749–1804). Jacob Temminck sponsored [[François Le Vaillant]] [1753–1824] to collect bird specimens in Southern Africa and Le Vaillant's six-volume {{Lang|fr|Histoire naturelle des oiseaux d'Afrique}} (1796–1808) included many non-African birds. His other bird books produced in collaboration with the artist Barraband are considered among the most valuable illustrated guides ever produced. [[Louis Pierre Vieillot]] (1748–1831) spent 10 years studying North American birds and wrote the {{Lang|fr|Histoire naturelle des oiseaux de l'Amerique septentrionale}} (1807–1808?). Vieillot pioneered in the use of life histories and habits in classification.<ref>{{cite web |author=White, Jeanne A. |title=Hill Collection — 18th c. French authors & artists |url=https://rmc.library.cornell.edu/ornithology/guide/hillguide10.htm|access-date=2007-12-01|date=1999-06-10 }}</ref> [[Alexander Wilson (ornithologist)|Alexander Wilson]] composed a nine-volume work, ''American Ornithology'', published 1808–1814, which is the first such record of North American birds, significantly antedating Audubon. In the early 19th century, [[Lewis and Clark]] studied and identified many birds in the western United States. [[John James Audubon]], born in 1785, observed and painted birds in France and later in the [[Ohio River|Ohio]] and [[Mississippi River|Mississippi]] valleys. From 1827 to 1838, Audubon published ''[[Birds of America (book)|The Birds of America]]'', which was engraved by [[Havell family|Robert Havell Sr.]] and his son Robert Havell Jr. Containing 435 engravings, it is often regarded as the greatest ornithological work in history.

===Scientific studies===
[[File:Bird eggs.jpg|thumb|left|Early bird study focused on collectibles such as eggs and nests.]]
The emergence of ornithology as a scientific discipline began in the 18th century, when [[Mark Catesby]] published his two-volume ''Natural History of Carolina, Florida, and the Bahama Islands'', a landmark work which included 220 hand-painted engravings and was the basis for many of the species [[Carl Linnaeus]] described in the 1758 ''[[10th edition of Systema Naturae|Systema Naturae]]''. Linnaeus' work revolutionised bird taxonomy by assigning every species a [[binomial nomenclature|binomial name]], categorising them into different genera. However, ornithology did not emerge as a specialised science until the Victorian era—with the popularization of natural history, and the collection of natural objects such as bird eggs and skins.<ref name="allen">{{cite book|author=Allen, David E.|year=1994|title=The naturalist in Britain: a social history|isbn=978-0691036328|publisher=Princeton University Press}}</ref><ref>{{cite book|author=Farber, Paul L.|year=1982|title=The Emergence of Ornithology as a Scientific Discipline, 1760–1850|publisher=D. Reidel Publishing Company, Boston}}</ref> This specialization led to the formation in Britain of the [[British Ornithologists' Union]] in 1858. In 1859, the members founded its journal ''[[The Ibis]]''. The sudden spurt in ornithology was also due in part to [[colonialism]]. At 100 years later, in 1959, [[Reginald Ernest Moreau|R. E. Moreau]] noted that ornithology in this period was preoccupied with the geographical distributions of various species of birds.<ref name="ibis-history">{{cite journal|author=Johnson, Kristin|year=2004|title=''The Ibis'': Transformations in a Twentieth Century British Natural History Journal|journal=Journal of the History of Biology|volume=37|pages=515–555| doi=10.1007/s10739-004-1499-3|issue=3|s2cid=83849594}}</ref>
{{Quote|No doubt the preoccupation with widely extended geographical ornithology, was fostered by the immensity of the areas over which British rule or influence stretched during the 19th century and for some time afterwards.|Moreau<ref>{{cite journal|author=Moreau, R. E.|year=1959|title=The Centenarian Ibis|journal=The Ibis|volume=101|pages=19–38|doi=10.1111/j.1474-919X.1959.tb02353.x}}</ref>}}

The bird collectors of the Victorian era observed the variations in bird forms and habits across geographic regions, noting local specialization and variation in widespread species. The collections of museums and private collectors grew with contributions from various parts of the world. The naming of species with binomials and the organization of birds into groups based on their similarities became the main work of museum specialists. The variations in widespread birds across geographical regions caused the introduction of trinomial names.
[[File:KaupClassification.svg|thumb|Kaup's classification of the crow family]]
The search for patterns in the variations of birds was attempted by many. [[Friedrich Wilhelm Joseph Schelling]] (1775–1854), his student [[Johann Baptist von Spix]] (1781–1826), and several others believed that a hidden and innate mathematical order existed in the forms of birds. They believed that a "natural" classification was available and superior to "artificial" ones. A particularly popular idea was the [[Quinarian system]] popularised by [[Nicholas Aylward Vigors]] (1785–1840), [[William Sharp Macleay]] (1792–1865), [[William Swainson]], and others. The idea was that nature followed a "rule of five" with five groups nested hierarchically. Some had attempted a rule of four, but [[Johann Jakob Kaup]] (1803–1873) insisted that the number five was special, noting that other natural entities such as the senses also came in fives. He followed this idea and demonstrated his view of the order within the crow family. Where he failed to find five genera, he left a blank insisting that a new genus would be found to fill these gaps. These ideas were replaced by more complex "maps" of affinities in works by [[Hugh Edwin Strickland]] and [[Alfred Russel Wallace]].<ref name=ohara>{{cite journal|author=O’Hara, Robert J.|year=1988|title=Diagrammatic classifications of birds, 1819–1901: views of the natural system in 19th-century British ornithology|pages=2746–2759 |journal=Acta XIX Congressus Internationalis Ornithologici|url=http://rjohara.net/cv/1988-ioc}}</ref><ref>{{Cite book|year=1975|isbn=978-0-674-64485-4|author=Stresemann, Erwin|title=Ornithology. From Aristotle to the Present|publisher=Harvard University Press|place=Cambridge, Massachusetts|pages=170–191}}</ref> A major advance was made by [[Max Fürbringer]] in 1888, who established a comprehensive phylogeny of birds based on anatomy, morphology, distribution, and biology. This was developed further by [[Hans Gadow]] and others.<ref>{{cite book|author=Fürbringer, Max |year=1888| title= Untersuchungen zur morphologie und systematik der vogel. Volume II. |place=Amsterdam| publisher= Verlag von TJ. Van Holkema|url= https://www.biodiversitylibrary.org/bibliography/51998| language=de}}</ref><ref>{{cite journal| author=Stresemann, E. |year=1959| title=The status of avian systematics and its unsolved problems| journal=Auk| volume=76|issue=3| pages=269–280| url=https://sora.unm.edu/sites/default/files/journals/auk/v076n03/p0269-p0280a.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://sora.unm.edu/sites/default/files/journals/auk/v076n03/p0269-p0280a.pdf |archive-date=2022-10-09 |url-status=live| doi=10.2307/4081807|jstor=4081807 |bibcode=1959Auk....76..269S }}</ref>

The [[Galapagos]] [[finch]]es were especially influential in the development of [[Charles Darwin]]'s theory of evolution. His contemporary [[Alfred Russel Wallace]] also noted these variations and the geographical separations between different forms leading to the study of [[biogeography]]. Wallace was influenced by the work of [[Philip Lutley Sclater]] on the distribution patterns of birds.<ref>{{cite journal|author=Sclater, P. L.|year=1858|title=On the general geographical distribution of the members of the class Aves|doi=10.1111/j.1096-3642.1858.tb02549.x|journal=Proc. Linn. Soc. Lond.|volume=9|pages=130–136|issue=7}}</ref>
[[File:SwainsonQuinarian.jpg|thumb|right|[[Quinarian system]] of bird classification by Swainson]]
For Darwin, the problem was how species arose from a common ancestor, but he did not attempt to find rules for delineation of species. The [[species problem]] was tackled by the ornithologist [[Ernst Mayr]], who was able to demonstrate that geographical isolation and the accumulation of genetic differences led to the [[Allopatric speciation|splitting of species]].<ref name=konishi>{{cite journal|author1=Konishi, Masakazu |author2=Emlen, Stephen T. |author3=Ricklefs, Robert E. |author4=Wingfield, John C.  |name-list-style=amp |year=1989|title=Contributions of Bird Studies to Biology|journal=Science|volume=246|issue=4929|pages=465–472|doi=10.1126/science.2683069|pmid=2683069|bibcode = 1989Sci...246..465K }}</ref><ref>{{cite journal|title=Ornithology and the genesis of the Synthetic Theory of Evolution|last=Junker|first=Thomas|journal=Avian Science|volume=3|issue=2&3|pages=65–73|year=2003|url=http://www.thomas-junker.homepage.t-online.de/pdf/03tjas.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.thomas-junker.homepage.t-online.de/pdf/03tjas.pdf |archive-date=2022-10-09 |url-status=live}}</ref>

Early ornithologists were preoccupied with matters of species identification. Only systematics counted as true science and field studies were considered inferior through much of the 19th century.<ref name=haffer/> In 1901, [[Robert Ridgway]] wrote in the introduction to ''The Birds of North and Middle America'' that:
{{Quote|There are two essentially different kinds of ornithology: systematic or scientific, and popular. The former deals with the structure and classification of birds, their synonymies, and technical descriptions. The latter treats of their habits, songs, nesting, and other facts pertaining to their life histories.}}
This early idea that the study of living birds was merely recreation held sway until ecological theories became the predominant focus of ornithological studies.<ref name=mayr/><ref name="ibis-history"/> The study of birds in their habitats was particularly advanced in Germany with [[bird ringing]] stations established as early as 1903. By the 1920s, the ''[[Journal für Ornithologie]]'' included many papers on the behaviour, ecology, anatomy, and physiology, many written by [[Erwin Stresemann]]. Stresemann changed the editorial policy of the journal, leading both to a unification of field and laboratory studies and a shift of research from museums to universities.<ref name=haffer>{{cite journal|journal=Archives of Natural History|volume=35|issue=1|pages=76–87|year=2008|title=The origin of modern ornithology in Europe|last=Haffer|first= Jürgen|author-link=Jürgen Haffer|doi=10.3366/E0260954108000077}}</ref> Ornithology in the United States continued to be dominated by museum studies of morphological variations, species identities, and geographic distributions, until it was influenced by Stresemann's student [[Ernst Mayr]].<ref name="barrow">{{cite book|author=Barrow, Mark V.|year=1998|title=A passion for birds: American ornithology after Audubon|publisher=Princeton University Press|isbn=978-0691049540}}</ref> In Britain, some of the earliest ornithological works that used the word ecology appeared in 1915.<ref>{{cite journal|author=Alexander, H. G.|year=1915|title=A Practical Study of Bird Ecology|journal=British Birds|volume=8|issue=9}}</ref> ''The Ibis'', however, resisted the introduction of these new methods of study, and no paper on ecology appeared until 1943.<ref name="ibis-history"/> The work of [[David Lack]] on population ecology was pioneering. Newer quantitative approaches were introduced for the study of ecology and behaviour, and this was not readily accepted. For instance, [[Claud Ticehurst]] wrote:
{{Quote|Sometimes it seems that elaborate plans and statistics are made to prove what is commonplace knowledge to the mere collector, such as that hunting parties often travel more or less in circles.|Ticehurst<ref name="ibis-history"/>}}
David Lack's studies on population ecology sought to find the processes involved in the regulation of population based on the evolution of optimal clutch sizes. He concluded that population was regulated primarily by [[Density-dependent inhibition|density-dependent controls]], and also suggested that natural selection produces life-history traits that maximize the fitness of individuals. Others, such as [[V. C. Wynne-Edwards|Wynne-Edwards]], interpreted population regulation as a mechanism that aided the [[Group selection|"species" rather than individuals]]. This led to widespread and sometimes bitter debate on what constituted the "unit of selection".<ref name=konishi/> Lack also pioneered the use of many new tools for ornithological research, including the idea of using [[Radar ornithology|radar]] to study bird migration.<ref>{{cite journal|author=Lack, David|year=1959|title=Watching migration by Radar|url=https://www.britishbirds.co.uk/wp-content/uploads/article_files/V52/V52_N08/V52_N08_P258_267_A056.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.britishbirds.co.uk/wp-content/uploads/article_files/V52/V52_N08/V52_N08_P258_267_A056.pdf |archive-date=2022-10-09 |url-status=live|journal=British Birds|volume=52|issue=8|pages=258–267}}</ref>

Birds were also widely used in studies of the niche hypothesis and [[Georgii Gause]]'s [[competitive exclusion]] principle. Work on resource partitioning and the structuring of bird communities through competition were made by [[Robert MacArthur]]. Patterns of [[biodiversity]] also became a topic of interest. Work on the relationship of the number of species to area and its application in the study of [[island biogeography]] was pioneered by [[E. O. Wilson]] and [[Robert MacArthur]].<ref name=konishi/> These studies led to the development of the discipline of [[landscape ecology]].
[[File:Red-footed Falcon.jpeg|thumb|left|A mounted specimen of a [[red-footed falcon]]]]
[[John Crook (ethologist)|John Hurrell Crook]] studied the behaviour of [[weaverbird]]s and demonstrated the links between ecological conditions, behaviour, and social systems.<ref name=konishi/><ref>{{cite journal|author=Crook, J. H.|author-link=John Crook (ethologist)|year=1964|title=The evolution of social organization and visual communication in the weaver birds (Ploceinae)|journal=Behaviour. Supplement|volume=10|pages=1–178}}</ref><ref name=Crook1980>{{Cite book | last=Crook| first=J. H. | title= The Evolution of Human Consciousness |publisher=Clarendon Press| year=1980| location=Oxford | pages=45–49| isbn=978-0-19-857174-2}}</ref> Principles from [[economics]] were introduced to the study of biology by Jerram L. Brown in his work on explaining territorial behaviour. This led to more studies of behaviour that made use of [[cost-benefit analyses]].<ref>{{cite journal|author=Brown, J. L.|year=1964|title=The evolution of diversity in avian territorial systems|journal=Wilson Bull.|volume=76|pages=160–169 |url=http://sora.unm.edu/sites/default/files/journals/wilson/v076n02/p0160-p0169.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sora.unm.edu/sites/default/files/journals/wilson/v076n02/p0160-p0169.pdf |archive-date=2022-10-09 |url-status=live}}</ref> The rising interest in [[sociobiology]] also led to a spurt of bird studies in this area.<ref name=konishi/><ref>{{cite journal|url=https://sora.unm.edu/node/636|title=Contents |journal = The Auk|date = 1981 |volume = 98 | number= 2|publisher = Searchable Ornithological Research Archive }}</ref>

The study of imprinting behaviour in ducks and geese by [[Konrad Lorenz]] and the studies of instinct in [[European herring gull|herring gull]]s by [[Nicolaas Tinbergen]] led to the establishment of the field of [[ethology]]. The study of learning became an area of interest and the study of [[Birdsong|bird songs]] has been a model for studies in neuroethology. The study of hormones and physiology in the control of behaviour has also been aided by bird models. These have helped in finding the [[Proximate and ultimate causation|proximate causes]] of circadian and seasonal cycles. Studies on migration have attempted to answer questions on the evolution of migration, orientation, and navigation.<ref name=konishi/>

The growth of genetics and the rise of molecular biology led to the application of the [[gene-centered view of evolution]] to explain avian phenomena. Studies on kinship and altruism, such as [[helpers at the nest|helpers]], became of particular interest. The idea of [[inclusive fitness]] was used to interpret observations on behaviour and life history, and birds were widely used models for testing hypotheses based on theories postulated by [[W. D. Hamilton]] and others.<ref name=konishi/>

The new tools of molecular biology changed the study of bird systematics, which changed from being based on [[phenotype]] to the underlying [[genotype]]. The use of techniques such as [[DNA–DNA hybridization]] to study evolutionary relationships was pioneered by [[Charles Sibley]] and [[Jon Edward Ahlquist]], resulting in what is called the [[Sibley–Ahlquist taxonomy]]. These early techniques have been replaced by newer ones based on [[mitochondrial DNA]] sequences and [[molecular phylogenetics]] approaches that make use of computational procedures for [[sequence alignment]], construction of [[phylogenetic tree]]s, and calibration of [[molecular clock]]s to infer evolutionary relationships.<ref>{{cite journal |author=O'Hara, Robert J.|year=1991|title=Essay review of Phylogeny and Classification of Birds: A Study in Molecular Evolution by Charles G. Sibley and Jon E. Ahlquist|journal=Auk|volume=108|issue=4|pages=990–994|url=http://rjohara.net/cv/1991-auk}}</ref><ref>{{cite journal|author=Slack, K.E, Delsuc, F., Mclenachan, P.A., Arnason, U. & D. Penny|year=2007|title=Resolving the root of the avian mitogenomic tree by breaking up long branches|journal=Molecular Phylogenetics and Evolution|volume=42|pmid=16854605|issue=1|pages=1–13|url=http://frederic.delsuc.neuf.fr/fd_fichiers/Slack-MolPhylogenetEvol07.pdf|doi=10.1016/j.ympev.2006.06.002|bibcode=2007MolPE..42....1S |citeseerx=10.1.1.561.5255|s2cid=6683688 |access-date=2007-11-30|archive-url=https://web.archive.org/web/20071130233730/http://frederic.delsuc.neuf.fr/fd_fichiers/Slack-MolPhylogenetEvol07.pdf|archive-date=2007-11-30|url-status=dead}}</ref> Molecular techniques are also widely used in studies of avian [[population biology]] and ecology.<ref>{{cite journal|author=Sorenson, M. D.|year=2002|title=Molecular Genetic Perspectives on Avian Brood Parasitism|journal=Integr. Comp. Biol.|volume=42|pages=388–400|doi=10.1093/icb/42.2.388|issue=2|pmid=21708732|last2=Payne|first2=RB|doi-access=free}}</ref>

===Rise to popularity===
The use of [[field glass]]es or [[telescope]]s for bird observation began in the 1820s and 1830s, with pioneers such as [[John Freeman Milward Dovaston|J. Dovaston]] (who also pioneered in the use of bird feeders), but instruction manuals did not begin to insist on the use of optical aids such as "a first-class telescope" or "field glass" until the 1880s.<ref>{{cite journal|author=Allen, D. E.|year=1967|doi=10.3366/jsbnh.1967.4.6.277|title=J. Dovaston-a Pioneer of Field Ornithology|journal=Journal of the Society for the Bibliography of Natural History  |volume=4|issue=6|page=280}}</ref><ref>{{cite journal|author=Hollerbach, Anne Larsen|year=1996|title=Of Sangfroid and Sphinx Moths: Cruelty, Public Relations, and the Growth of Entomology in England, 1800–1840|journal=Osiris |series=2nd Series|volume=11|pages=201–220|doi=10.1086/368760|s2cid=143634420}}</ref>

[[File:VillageBirdsFlorenceMerriam.jpg|thumb|Page from an early field guide by [[Florence Augusta Merriam Bailey]]]]
The rise of field guides for the identification of birds was another major innovation. The early guides such as [[History of British Birds|Thomas Bewick's two-volume guide]] and [[History of British Birds (1843)|William Yarrell's three-volume guide]] were cumbersome, and mainly focused on identifying specimens in the hand. The earliest of the new generation of field guides was prepared by [[Florence Augusta Merriam Bailey|Florence Merriam]], sister of [[Clinton Hart Merriam]], the mammalogist. This was published in 1887 in a series ''Hints to Audubon Workers: Fifty Birds and How to Know Them'' in Grinnell's ''[[Audubon Magazine]]''.<ref name="barrow"/> These were followed by new field guides,<ref>{{cite web|last=Dunlap |first=Tom|title=Tom Dunlap on Early Bird Guides. Environmental History January 2005|url=http://www.historycooperative.org/journals/eh/10.1/gallery.html|access-date=2007-11-24}}</ref> 
from the pioneering illustrated handbooks of [[Frank Chapman (ornithologist)|Frank Chapman]] to the classic ''[[Field Guide to the Birds]]'' by [[Roger Tory Peterson]] in 1934, to ''[[Birds of the West Indies]]'' published in 1936 by [[James Bond (ornithologist)|Dr. James Bond]] - the same who inspired the amateur ornithologist [[Ian Fleming]] in naming his [[James Bond (literary character)|famous literary spy]].<ref>{{cite news |last1=Briand |first1=Frederic |title=From Bird Scientist to Spy: the Name is Bond, James Bond. |url=https://www.researchgate.net/publication/364995351 |work=National Geographic |date=November 2012}}</ref>

The interest in [[birdwatching]] grew in popularity in many parts of the world, and the possibility for amateurs to contribute to biological studies was soon realized. As early as 1916, [[Julian Huxley]] wrote a two-part article in ''[[The Auk]]'', noting the tensions between amateurs and professionals, and suggested the possibility that the "vast army of bird lovers and bird watchers could begin providing the data scientists needed to address the fundamental problems of biology."<ref>{{cite journal|last=Huxley |first=Julian|author-link=Julian Huxley|year=1916|title=Bird-watching and biological science (part 1)|journal=Auk|volume=33|issue=2|pages=142–161|url=http://sora.unm.edu/sites/default/files/journals/auk/v033n02/p0142-p0161.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sora.unm.edu/sites/default/files/journals/auk/v033n02/p0142-p0161.pdf |archive-date=2022-10-09 |url-status=live|doi=10.2307/4072162|jstor=4072162}}</ref><ref>{{cite journal|author=Huxley, J.|year=1916|title=Bird-watching and biological science (part 2)|journal=Auk|volume=33|issue=3|pages=256–270|url=http://sora.unm.edu/sites/default/files/journals/auk/v033n03/p0256-p0270.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sora.unm.edu/sites/default/files/journals/auk/v033n03/p0256-p0270.pdf |archive-date=2022-10-09 |url-status=live|doi=10.2307/4072322|jstor=4072322}}</ref> The amateur ornithologist [[Harold F. Mayfield]] noted that the field was also funded by non-professionals. He noted that in 1975, 12% of the papers in American ornithology journals were written by persons who were not employed in biology related work.<ref>{{cite journal|last=Mayfield |first=Harold F.|year=1979|title=The amateur in ornithology|url=https://sora.unm.edu/sites/default/files/journals/auk/v096n01/p0168-p0171.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://sora.unm.edu/sites/default/files/journals/auk/v096n01/p0168-p0171.pdf |archive-date=2022-10-09 |url-status=live|journal=The Auk|volume=96|issue=1|pages=168–171|doi=10.1093/auk/96.1.168}}</ref>

Organizations were started in many countries, and these grew rapidly in membership, most notable among them being the [[Royal Society for the Protection of Birds]] (RSPB) in Britain and the [[Audubon Society]] in the US, which started in 1885. Both these organizations were started with the primary objective of conservation. The RSPB, born in 1889, grew from a small [[Croydon]]-based group of women, including [[Eliza Phillips]], [[Etta Lemon]], Catherine Hall and [[Hannah Poland]]. Calling themselves the "Fur, Fin, and Feather Folk", the group met regularly and took a pledge "to refrain from wearing the feathers of any birds not killed for the purpose of food, the [[ostrich]] only exempted." The organization did not allow men as members initially, avenging a policy of the [[British Ornithologists' Union]] to keep out women.<ref name="allen"/> Unlike the RSPB, which was primarily conservation oriented, the [[British Trust for Ornithology]] was started in 1933 with the aim of advancing ornithological research. Members were often involved in collaborative ornithological projects. These projects have resulted in atlases which detail the distribution of bird species across Britain.<ref name=bibby2003>{{cite journal|last=Bibby |first=Colin J.|year=2003|title=Fifty years of Bird Study: Capsule Field ornithology is alive and well, and in the future can contribute much more in Britain and elsewhere|journal=Bird Study|volume=50|issue=3|pages=194–210|doi=10.1080/00063650309461314 |s2cid=87377120}}</ref> In Canada, citizen scientist [[Elsie Cassels]] studied migratory birds and was involved in establishing Gaetz Lakes bird sanctuary.<ref>{{Cite book|title=Fish, fur & feathers : fish and wildlife conservation in Alberta 1905-2005.|date=2005|publisher=Fish and Wildlife Historical Society|others=Federation of Alberta Naturalists., Fish and Wildlife Historical Society.|isbn=0-9696134-7-4|location=Edmonton|oclc=62181407}}</ref> In the United States, the [[Breeding bird survey|Breeding Bird Surveys]], conducted by the [[United States Geological Survey]], have also produced atlases with information on breeding densities and changes in the density and distribution over time. Other volunteer collaborative ornithology projects were subsequently established in other parts of the world.<ref>{{cite web|url=https://www.pwrc.usgs.gov/BBS/|title=North American Breeding Bird Survey}}</ref>