Editing Ornithology (section)

==Techniques==
The tools and techniques of ornithology are varied, and new inventions and approaches are quickly incorporated. The techniques may be broadly dealt under the categories of those that are applicable to specimens and those that are used in the field, but the classification is rough and many analysis techniques are usable both in the laboratory and field or may require a combination of field and laboratory techniques.

===Collections===
{{main|Bird collections}}
[[File:Godwit prep.jpg|thumb|left|Bird-preservation techniques]]
The earliest approaches to modern bird study involved the collection of eggs, a practice known as [[oology]]. While collecting became a pastime for many amateurs, the labels associated with these early egg collections made them unreliable for the serious study of bird breeding. To preserve eggs, a tiny hole was made and the contents extracted. This technique became standard with the invention of the blow drill around 1830.<ref name=allen /> Egg collection is no longer popular; however, historic museum collections have been of value in determining the effects of [[pesticide]]s such as [[DDT]] on physiology.<ref>{{cite book|author=Newton, I.|year=1979|title=Population ecology of raptors|isbn=978-0856610233|publisher=T. & A. D. Poyser, Berkhamsted}}</ref><ref>{{cite journal|author1=Green, Rhys E.|author2=Scharlemann, Jörn P. W.|name-list-style=amp|year=2003|title=Egg and skin collections as a resource for long-term ecological studies|journal=Bull. B.O.C.|volume=123A|pages=165–176|url=http://www.boc-online.org/PDF/124GreenEggAndSkin.pdf|access-date=2007-05-20|archive-url=https://web.archive.org/web/20070630190602/http://www.boc-online.org/PDF/124GreenEggAndSkin.pdf|archive-date=2007-06-30|url-status=dead}}</ref> Museum [[bird collections]] continue to act as a resource for taxonomic studies.<ref>{{cite journal|author=Winker, K.|year=2004|title=Natural history museums in a postbiodiversity era|journal=BioScience|volume=54|pages=455–459|doi=10.1641/0006-3568(2004)054[0455:NHMIAP]2.0.CO;2|issue=5|doi-access=free}}</ref>
[[File:BirdMorpho.svg|thumb|Morphometric measurements of birds are important in systematics.]]
The use of bird skins to document species has been a standard part of systematic ornithology. Bird skins are prepared by retaining the key bones of the wings, legs, and skull along with the skin and feathers. In the past, they were treated with [[arsenic]] to prevent fungal and insect (mostly [[Dermestidae|dermestid]]) attack. Arsenic, being toxic, was replaced by less-toxic [[borax]]. Amateur and professional collectors became familiar with these skinning techniques and started sending in their skins to museums, some of them from distant locations. This led to the formation of huge collections of bird skins in museums in Europe and North America. Many private collections were also formed. These became references for comparison of species, and the ornithologists at these museums were able to compare species from different locations, often places that they themselves never visited. [[Morphometrics]] of these skins, particularly the lengths of the tarsus, bill, tail, and wing became important in the descriptions of bird species. These skin collections have been used in more recent times for studies on [[molecular phylogenetics]] by the extraction of [[ancient DNA]]. The importance of [[biological type|type specimens]] in the description of species make skin collections a vital resource for systematic ornithology. However, with the rise of molecular techniques,  establishing the taxonomic status of new discoveries, such as the [[Bulo Burti boubou]] (''Laniarius liberatus'', no longer a valid species) and the [[Bugun liocichla]] (''Liocichla bugunorum''), using blood, DNA and feather samples as the [[holotype]] material, has now become possible.

Other methods of preservation include the storage of specimens in spirit. Such wet specimens have special value in physiological and anatomical study, apart from providing better quality of DNA for molecular studies.<ref>{{cite journal|author=Livezey, Bradley C.|year=2003|title=Avian spirit collections: attitudes, importance and prospects|journal=Bull. B.O.C.|volume=123A|pages=35–51|url=http://www.carnegiemnh.net/birds/Livezey%20(2003).pdf|access-date=2007-05-20|archive-url=https://web.archive.org/web/20070630190602/http://www.carnegiemnh.net/birds/Livezey%20(2003).pdf|archive-date=2007-06-30|url-status=dead}}</ref> [[Freeze drying]] of specimens is another technique that has the advantage of preserving stomach contents and anatomy, although it tends to shrink, making it less reliable for morphometrics.<ref>{{cite journal|author=Winker, K.|year=1993|title=Specimen shrinkage in Tennessee warblers and Traill's flycatchers|journal=J. Field Ornithol.|volume=64|issue=3|pages=331–336|url=http://www.uaf.edu/museum/bird/personnel/KWinker/Winker%20shrinkage%20JFO%201993.pdf|url-status=dead|archive-url=https://web.archive.org/web/20070630190602/http://www.uaf.edu/museum/bird/personnel/KWinker/Winker%20shrinkage%20JFO%201993.pdf|archive-date=2007-06-30}}</ref><ref>{{cite journal|author=Bjordal, H.|year=1983|title=Effects of deep freezing, freeze-drying and skinning on body dimensions of House Sparrows (''Passer domesticus'')|journal=Cinclus|volume=6|pages=105–108}}</ref>

===In the field===
The study of birds in the field was helped enormously by improvements in optics. Photography made it possible to document birds in the field with great accuracy. High-power spotting scopes today allow observers to detect minute morphological differences that were earlier possible only by examination of the specimen "in the hand".<ref name="shorebirds">{{cite book|author1=Hayman, Peter |author2=Marchant, John |author3=Prater, Tony  |name-list-style=amp |year=1986|title=Shorebirds: An Identification Guide to the Waders of the World|isbn=978-0395602379|publisher=Croom Helm, London}}</ref>
[[File:Mist net kinglet.jpg|thumb|left|A bird caught in a [[mist net]]]]
The capture and marking of birds enable detailed studies of life history. Techniques for capturing birds are varied and include the use of [[birdlime|bird liming]] for perching birds, [[mist net]]s for woodland birds, [[cannon netting]] for open-area flocking birds, the ''[[bal-chatri]]'' trap for raptors,<ref>{{cite journal|author1=Berger D. D.  |author2=Mueller, H. C.  |name-list-style=amp |year=1959|title=The Bal-Chatri: a trap for the birds of prey|journal=Bird-Banding|volume=30|issue=1  |pages=19–27|url=http://sora.unm.edu/sites/default/files/journals/jfo/v030n01/p0018-p0026.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sora.unm.edu/sites/default/files/journals/jfo/v030n01/p0018-p0026.pdf |archive-date=2022-10-09 |url-status=live|doi=10.2307/4510726|jstor=4510726  }}</ref> decoys and [[Heligoland trap|funnel traps]] for water birds.<ref>{{cite web|url=http://www.pwrc.usgs.gov/resshow/perry/scoters/CaptureTechniques.htm|publisher=USGS|title=Techniques to capture Seaducks in the Chesapeake Bay and Restigouche River|access-date=2007-12-01}}</ref><ref>{{cite book|author1=Ralph, C. John |author2=Geupel, Geoffrey R. |author3=Pyle, Peter |author4=Martin, Thomas E. |author5=DeSante, David F.  |name-list-style=amp |year=1993|title=Handbook of field methods for monitoring landbirds. Gen. Tech. Rep. PSW-GTR-144-www. Albany, CA|publisher=Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture|url=http://www.fs.fed.us/psw/publications/documents/psw_gtr144/psw_gtr144.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.fs.fed.us/psw/publications/documents/psw_gtr144/psw_gtr144.pdf |archive-date=2022-10-09 |url-status=live}}</ref>
[[File:Monitoreo de Aves a Largo Plazo.jpg|thumb|A researcher measures a wild woodpecker.  The bird's right leg has a metal identification tag.]]
The bird in the hand may be examined and [[morphometrics|measurements]] can be made, including standard lengths and weights. Feather moult and skull ossification provide indications of age and health. Sex can be determined by examination of anatomy in some sexually nondimorphic species. Blood samples may be drawn to determine hormonal conditions in studies of physiology, identify DNA markers for studying genetics and kinship in studies of breeding biology and phylogeography. Blood may also be used to identify pathogens and [[arthropod-borne virus]]es. [[Ectoparasite]]s may be collected for studies of coevolution and [[zoonoses]].<ref>{{cite journal|author1=Walther, B. A.  |author2=Clayton, D. H.  |name-list-style=amp |year=1997|title=Dust-ruffling: A simple method for quantifying ectoparasite loads of live birds|journal=J. Field Ornithol.|volume=68|issue=4|pages=509–518|url=http://sora.unm.edu/sites/default/files/journals/jfo/v068n04/p0509-p0518.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sora.unm.edu/sites/default/files/journals/jfo/v068n04/p0509-p0518.pdf |archive-date=2022-10-09 |url-status=live }}</ref> In many cryptic species, measurements (such as the relative lengths of wing feathers in warblers) are vital in establishing identity.[[File:Condor in flight.JPG|thumb|A [[California condor]] marked with wing tags]] Captured birds are often marked for future recognition. [[bird ringing|Rings or bands]] provide long-lasting identification, but require capture for the information on them to be read. Field-identifiable marks such as coloured bands, wing tags, or dyes enable short-term studies where individual identification is required. [[Mark and recapture]] techniques make [[demographic]] studies possible. Ringing has traditionally been used in the study of migration. In recent times, satellite transmitters provide the ability to track migrating birds in near-real time.<ref>{{cite journal|doi=10.2307/4512291|author1=Marion, W. R.  |author2=Shamis, J. D.  |name-list-style=amp |year=1977|title=An annotated bibliography of bird marking techniques|journal=Bird-Banding|volume=48|issue=1|pages=42–61|url=http://sora.unm.edu/sites/default/files/journals/jfo/v048n01/p0042-p0061.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sora.unm.edu/sites/default/files/journals/jfo/v048n01/p0042-p0061.pdf |archive-date=2022-10-09 |url-status=live|jstor=4512291}}</ref>

Techniques for estimating [[population density]] include [[Avian ecology field methods#Point counts and area searches|point count]]s, [[transect]]s, and territory mapping. Observations are made in the field using carefully designed protocols and the data may be analysed to estimate bird diversity, relative abundance, or absolute population densities.<ref name="bibby">{{cite book|author1=Bibby C., Jones M.|author2=Marsden, S.|name-list-style=amp|year=1998|title=Expedition Field Techniques – Bird Surveys|publisher=Expedition Advisory Centre, Royal Geographical Society, London.|url=http://conservation.bp.com/advice/field.asp|access-date=2007-11-16|archive-url=https://web.archive.org/web/20071206063639/http://conservation.bp.com/advice/Field.asp|archive-date=2007-12-06|url-status=dead}}</ref> These methods may be used repeatedly over large timespans to monitor changes in the environment.<ref>{{cite book|year=2006|title=Monitoring bird populations in small geographic areas|publisher=Canadian Wildlife Service|url=http://dsp-psd.pwgsc.gc.ca/Collection/CW66-259-2006E.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://dsp-psd.pwgsc.gc.ca/Collection/CW66-259-2006E.pdf |archive-date=2022-10-09 |url-status=live|vauthors=Dunn EH, Bart J, Collins BT, Craig B, Dale B, Downes CM, Francis CM, Woodley S }}</ref> [[Camera trap]]s have been found to be a useful tool for the detection and documentation of elusive species, nest predators and in the quantitative analysis of frugivory, seed dispersal and behaviour.<ref>{{cite book|author=Winarni, N., Carroll, J.P. & O'Brien, T.G|year=2005|title=The application of camera traps to the study of Galliformes in southern Sumatra, Indonesia. pp. 109–121 in: Fuller, R.A. & Browne, S.J. (eds) 2005. Galliformes 2004. Proceedings of the 3rd International Galliformes Symposium|publisher=World Pheasant Association, Fordingbridge, UK}}</ref><ref>{{cite journal|author1=O'Brien, Timothy G.  |author2=Kinnaird, Margaret F. |name-list-style=amp |year=2008|title= A picture is worth a thousand words: the application of camera trapping to the study of birds|journal=Bird Conservation International|volume=18|pages=S144–S162|doi=10.1017/S0959270908000348 |doi-access=free}}</ref>

===In the laboratory===
Many aspects of bird biology are difficult to study in the field. These include the study of behavioural and physiological changes that require a long duration of access to the bird. Nondestructive samples of blood or feathers taken during field studies may be studied in the laboratory. For instance, the variation in the ratios of stable hydrogen isotopes across latitudes makes establishing the origins of migrant birds possible using [[mass spectrometry|mass spectrometric]] analysis of feather samples.<ref>{{cite journal|author=Hobson, K. A. Hobson, Steven Van Wilgenburg, Leonard I. Wassenaar, Helen Hands, William P. Johnson, Mike O'Meilia & Philip Taylor|year=2006|title=Using Stable Hydrogen Isotope Analysis of Feathers to Delineate Origins of Harvested Sandhill Cranes in the Central Flyway of North America|journal=Waterbirds|volume=29|issue=2|pages=137–147|doi=10.1675/1524-4695(2006)29[137:USHIAO]2.0.CO;2|s2cid=54943028 }}</ref> These techniques can be used in combination with other techniques such as ringing.<ref>{{cite book|author=Berthold, P., Gwinner, Eberhard and Sonnenschein, Edith |year=2003|title=Avian Migration|publisher=Springer|isbn=978-3540434085}}</ref>

The first attenuated vaccine developed by [[Louis Pasteur]], for fowl cholera, was tested on poultry in 1878.<ref>{{cite journal|author=Pasteur, Louis|year=1880|title=De l'attenuation du virus du chokra des poules|journal=Comptes Rendus de l'Académie des Sciences|volume=91|pages=673–680|url=http://www.asm.org/ccLibraryFiles/FILENAME/0000000222/1880p126.pdf|access-date=2010-08-29|archive-url=https://web.archive.org/web/20100612200422/http://asm.org/ccLibraryFiles/FILENAME/0000000222/1880p126.pdf|archive-date=2010-06-12|url-status=dead}}</ref> Anti-malarials were tested on birds which harbour avian-malarias.<ref>{{cite journal| author=Manwell, Reginald D. |year=1949| title= Malaria, birds and war. |jstor=9773656|journal=American Scientist |volume=37| issue=1| pages=60–68|pmid=18123477}}</ref> Poultry continues to be used as a model for many studies in non-mammalian immunology.<ref>{{Cite book|author=Davison, Fred, Bernd Kaspers & Karel Schat (Eds.)|year=2008|publisher=Academic Press|isbn=978-0-12-370634-8|title=Avian Immunology}}</ref>

Studies in bird behaviour include the use of tamed and trained birds in captivity. Studies on [[bird intelligence]] and [[bird vocalization#Learning|song learning]] have been largely laboratory-based. Field researchers may make use of a wide range of techniques such as the use of dummy owls to elicit mobbing behaviour, and dummy males or the use of call playback to elicit territorial behaviour and thereby to establish the boundaries of bird territories.<ref>{{cite journal|author=Slater, P. J. B.|year=2003|title=Fifty years of bird song research: a case study in animal behaviour|journal=Animal Behaviour|volume=65|pages=633–639|doi=10.1006/anbe.2003.2051|issue=4|s2cid=53157104|url=http://www.escholarship.org/uc/item/6bz1v7pf}}</ref>[[File:EmlenFunnel.svg|thumb|An Emlen funnel is used to study the orientation behaviour of migratory birds in a laboratory. Experimenters sometimes place the funnel inside a planetarium to study night migration.]] Studies of [[bird migration]] including aspects of navigation, orientation, and physiology are often studied using captive birds in special cages that record their activities. The [[Emlen funnel]], for instance, makes use of a cage with an inkpad at the centre and a conical floor where the ink marks can be counted to identify the direction in which the bird attempts to fly. The funnel can have a transparent top and visible cues such as the direction of sunlight may be controlled using mirrors or the positions of the stars simulated in a [[planetarium]].<ref>{{cite journal|author1=Emlen, S. T.  |author2=Emlen, J. T.  |name-list-style=amp |year=1966|title=A technique for recording migratory orientation of captive birds|jstor=4083048|url=http://sora.unm.edu/node/21524|journal=Auk|volume=83|pages=361–367|doi=10.2307/4083048|issue=3|doi-access=free}}</ref>

The entire genome of the domestic fowl (''[[Gallus gallus]]'') was sequenced in 2004, and was followed in 2008 by the genome of the zebra finch (''[[Taeniopygia guttata]]'').<ref>{{cite web |url=http://songbirdgenome.org/ |title=Zebra finch genome assembly release |access-date=7 May 2009 |date=6 Aug 2008 |publisher=The songbird genome sequencing project |archive-url=https://web.archive.org/web/20090805084309/http://songbirdgenome.org/ |archive-date=5 August 2009 |url-status=dead }}</ref>  Such whole-genome sequencing projects allow for studies on evolutionary processes involved in [[speciation]].<ref>{{cite journal|title=Identification of Birds through DNA Barcodes|vauthors=Hebert PD, Stoeckle MY, Zemlak TS, Francis CM |journal=PLOS Biology|volume= 2|issue=10|pages=e312|doi=10.1371/journal.pbio.0020312|year=2004|pmid=15455034|pmc=518999 |doi-access=free }}</ref> Associations between the expression of genes and behaviour may be studied using candidate genes. Variations in the exploratory behaviour of great tits (''[[Parus major]]'') have been found to be linked with a gene orthologous to the human gene ''[[DRD4]]'' (Dopamine receptor D4) which is known to be associated with novelty-seeking behaviour.<ref>{{cite journal |vauthors=Fidler AE, van Oers K, Drent PJ, Kuhn S, Mueller JC, Kempenaers B |title=Drd4 gene polymorphisms are associated with personality variation in a passerine bird |journal=Proc. Biol. Sci. |volume=274 |issue=1619 |pages=1685–91 |year=2007  |pmid=17472912 |pmc=1914334 |doi=10.1098/rspb.2007.0337 }}</ref> The role of gene expression in developmental differences and morphological variations have been studied in [[Darwin's finches]]. The difference in the expression of ''Bmp4'' have been shown to be associated with changes in the growth and shape of the beak.<ref>{{cite journal|last1=Abzhanov |first1=Arhat | last2=Protas | first2=Meredith |last3=Grant | first3=Peter R. | last4=Tabin | first4=Clifford J. |year=2004|title=Bmp4 and morphological variation of beaks in Darwin's finches|journal=Science|volume=305|pages=1462–1465|doi=10.1126/science.1098095|pmid=15353802|issue=5689|bibcode = 2004Sci...305.1462A |s2cid=17226774 }}</ref><ref>{{cite journal|title=High-speed developments in avian genomics|last1=Bonneaud | first1=Camille | last2=Burnside | first2=Joan |last3=Edwards | first3=Scott V. |name-list-style=amp |journal=BioScience|year=2008|volume=58|issue=7|pages=587–595|doi=10.1641/B580706|s2cid=17239411 |url=https://dash.harvard.edu/bitstream/handle/1/2665788/Edwards_High-speedDevelopments.pdf?sequence=2|doi-access=free}}</ref>

The chicken has long been a [[model organism]] for studying vertebrate [[developmental biology]]. As the embryo is readily accessible, its development can be easily followed (unlike [[house mouse|mice]]). This also allows the use of [[electroporation]] for studying the effect of adding or silencing a gene. Other tools for perturbing their genetic makeup are chicken [[embryonic stem cell]]s and [[viral vector]]s.<ref>{{cite journal |last=Stern | first=Claudio D. |title=The chick; a great model system becomes even greater |journal=Dev. Cell |volume=8 |issue=1 |pages=9–17 |date=January 2005 |pmid=15621526 |doi=10.1016/j.devcel.2004.11.018|doi-access=free }}</ref>

===Collaborative studies===
[[File:CanadaGooseSummer19942003.png|thumb|right|Summer distribution and abundance of [[Canada goose]] using data from the North American Breeding Bird Surveys 1994–2003]]
With the widespread interest in birds,  use of a large number of people to work on collaborative ornithological projects that cover large geographic scales has been possible.<ref>{{cite journal|first1=Caren B. | last1=Cooper | author-link=Caren Cooper | first2=Janis | last2=Dickinson | first3=Tina | last3=Phillips | first4=Rick | last4=Bonney|year=2007|title=Citizen science as a tool for conservation in residential ecosystems|journal=Ecology and Society|volume=12|issue=2|page=11|doi=10.5751/ES-02197-120211|doi-access=free|hdl=10535/2968|hdl-access=free}}</ref><ref>{{cite journal|author=Greenwood, J.J.D.|year=2007|title=Citizens, science and bird conservation|journal=Journal of Ornithology|volume=148|issue=1|pages=77–124|doi=10.1007/s10336-007-0239-9|bibcode=2007JOrn..148...77G |s2cid=21914046|url=http://www.dof.dk/sider/images/stories/gu/vu/dokumenter/greenwood_vu.pdf|url-status=dead|archive-url=https://web.archive.org/web/20110719123722/http://www.dof.dk/sider/images/stories/gu/vu/dokumenter/greenwood_vu.pdf|archive-date=2011-07-19}}</ref> These [[citizen science]] projects include nationwide projects such as the [[Christmas Bird Count]],<ref>{{cite book|author=Wing, L.|year=1947|title=Christmas census summary 1900–1939|publisher=State College of Washington, Pullman. Mimeograph.}}</ref> Backyard Bird Count,<ref>{{cite web|url=http://www.birdsource.org/gbbc|title=Great Backyard Bird Count}}</ref> the North American [[Breeding Bird Survey]], the Canadian EPOQ<ref>{{cite web|url=http://www.oiseauxqc.org/epoq.html|title=Étude des populations d'oiseaux du Québec|work=oiseauxqc.org}}</ref> or regional projects such as the Asian Waterfowl Census and [http://www.springalive.net/world Spring Alive] in Europe. These projects help to identify distributions of birds, their population densities and changes over time, arrival and departure dates of migration, breeding seasonality, and even population genetics.<ref>{{cite web|url=http://www.birds.cornell.edu/programs/urbanbirds/ubs_PIWMainEN.html|title=Project PigeonWatch}}</ref> The results of many of these projects are published as [[bird atlas]]es. Studies of migration using bird ringing or colour marking often involve the cooperation of people and organizations in different countries.<ref>[http://www.euring.org/ EURING Coordinated bird-ringing in Europe]. Euring.org. Retrieved on 2013-02-22.</ref>