Content deleted Content added
m →External links: iw nn |
198.41.70.101 (talk) ←Replaced content with 'Auston was here' Tag: blanking |
||
Line 1: | Line 1: | ||
Auston was here |
|||
[[Image:BrantaLeucopsisMigration.jpg|thumb|300px|A flock of [[Barnacle Goose|Barnacle Geese]] during autumn migration]] |
|||
[[Image:Migrationroutes.svg|thumb|Some migration routes]] |
|||
'''Bird migration''' is the regular seasonal journey undertaken by many species of [[bird]]s. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular (nomadism, invasions, irruptions) or in only one direction (dispersal, movement of young away from natal area). Migration is marked by its annual seasonality.<ref>{{cite book|title=Bird Migration: A General Survey|author=Peter Berthold, Hans-Günther Bauer, Valerie Westhead |
|||
|year=2001|isbn=0198507879|publisher=[[Oxford University Press]]|location=Oxford}}</ref> In contrast, birds that are non-migratory are said to be resident or sedentary. Approximately 1800 of the world's 10,000 bird species are long-distance migrants. <ref>{{cite journal|author=Sekercioglu, C.H.|year=2007|title=Conservation ecology: area trumps mobility in fragment bird extinctions|journal=Current Biology |volume=17|pages=R283–R286|doi=10.1016/j.cub.2007.02.019|pmid=17437705|issue=8}}</ref> |
|||
==General patterns== |
|||
[[Image:101111 Maison 007.jpg|thumb|Flocks of birds assembling before migration southwards (probably [[Sturnus vulgaris]])]] |
|||
Many bird populations migrate long distances along a [[flyway]]. The most common pattern involves flying north in the spring to breed in the temperate or [[Arctic]] summer and returning in the autumn to wintering grounds in warmer regions to the south. Of course, in the Southern Hemisphere the directions are reversed, but there is less land area in the far South to support long-distance migration. |
|||
The primary motivation for migration appears to be food; for example, some hummingbirds choose not to migrate if fed through the winter. Also, the longer days of the northern summer provide extended time for [[breeding in the wild|breeding]] birds to feed their young. This helps [[Diurnality|diurnal]] birds to produce larger [[Clutch (eggs)|clutch]]es than related non-migratory species that remain in the tropics. As the days shorten in autumn, the birds return to warmer regions where the available food supply varies little with the season. |
|||
These advantages offset the high stress, physical exertion costs, and other risks of the migration such as predation. Predation can be heightened during migration: the [[Eleonora's Falcon]], which breeds on [[Mediterranean Sea|Mediterranean]] islands, has a very late breeding season, coordinated with the autumn passage of southbound [[passerine]] migrants, which it feeds to its young. A similar strategy is adopted by the [[Greater Noctule bat]], which preys on nocturnal passerine migrants.<ref>{{cite journal|author=Dondini, G., Vergari, S. |year=2000|title=Carnivory in the greater noctule bat (''Nyctalus lasiopterus'') in Italy.|journal=Journal of Zoology |volume=251|pages=233–236|doi=10.1111/j.1469-7998.2000.tb00606.x}}</ref><ref name=bats>{{cite journal|author=Popa-Lisseanu, A. G., Delgado-Huertas, A., Forero, M. G., Rodriguez, A., Arlettaz, R. & Ibanez, C. |year=2007 |title=Bats' conquest of a formidable foraging niche: the myriads of nocturnally migrating songbirds.| journal=PLoS ONE|volume=2|issue=2|page=e205|doi=10.1371/journal.pone.0000205|pmid=17299585|pmc=1784064}}</ref><ref>{{cite journal|author=Ibáñez, C., Juste, J., García-Mudarra, J. L., Agirre-Mendi, P. T. |year=2001|title=Bat predation on nocturnally migrating birds.|journal=PNAS|volume=98|pages=9700–9702|url=http://www.pnas.org/cgi/content/full/98/17/9700#B8|doi=10.1073/pnas.171140598|pmid=11493689|issue=17|pmc=55515}}</ref> The higher concentrations of migrating birds at stopover sites make them prone to parasites and pathogens, which require a heightened immune response.<ref name=newton/> |
|||
Within a species not all populations may be migratory; this is known as "partial migration". Partial migration is very common in the southern continents; in Australia, 44% of non-passerine birds and 32% of passerine species are partially migratory.<ref>{{cite journal|author=Chan K|year=2001|title=Partial migration in Australian landbirds: a review.|journal=Emu|volume=101|issue=4|pages=281–292|doi=10.1071/MU00034}}</ref> In some species, the population at higher latitudes tends to be migratory and will often winter at lower latitude. The migrating birds bypass the latitudes where other populations may be sedentary, where suitable wintering habitats may already be occupied. |
|||
This is an example of ''leap-frog migration''.<ref>{{cite journal|author=Boland, J. M.|year=1990|title=Leapfrog migration in North American shorebirds: intra- and interspecific examples.|journal=The Condor |volume=92|pages=284–290|url=http://elibrary.unm.edu/sora/Condor/files/issues/v092n02/p0284-p0290.pdf|format=PDF|doi=10.2307/1368226|issue=2|jstor=1368226|publisher=The Condor, Vol. 92, No. 2}}</ref> Many fully-migratory species show leap-frog migration (birds that nest at higher latitudes spend the winter at lower latitudes), and many show the alternative, "chain migration" where populations 'slide' more evenly North and South without reversing order. |
|||
Within a population, it is common for different ages and/or sexes to have different patterns of timing and distance. Only the female [[Chaffinch]]es in [[Scandinavia]] migrate, with the males staying resident. This has given rise to the latter's specific name of ''coelebs'', a bachelor. |
|||
Most migrations begin with the birds starting off in a broad front. Often, this front narrows into one or more preferred routes termed [[flyway]]s. These routes typically follow mountain ranges or coastlines, sometimes rivers, and may take advantage of updrafts and other wind patterns or avoid geographical barriers such as large stretches of open water. The specific routes may be [[genetic programming|genetically programmed]] or learned to varying degrees. The routes taken on forward and return migration are often different.<ref name=newton>{{cite book|author=Newton, I. |year=2008|title=The Migration Ecology of Birds.|publisher= Elselvier|isbn=9780125173674}}</ref> A common pattern in North America is clockwise migration, where birds flying North tend to be further West, and flying South tend to shift Eastwards. |
|||
Many, if not most, birds migrate in flocks. For larger birds, flying in flocks reduces the energy cost. Geese in a V-formation may conserve 12–20 % of the energy they would need to fly alone.<ref>Hummel, D. & Beukenberg, M. (1989). "Aerodynamische Interferenzeffekte beim Formationsfl ug von Vogeln", ''J. Ornithol.'' 130: 15–24.</ref><ref>{{cite journal|author=Cutts, C. J. & J R Speakman|year=1994|title=Energy savings in formation flight of Pink-footed Geese.|journal= J. Exp. Biol.|volume= 189|pages=251–261 |url=http://jeb.biologists.org/cgi/reprint/189/1/251.pdf |format=PDF|pmid=9317742|issue=1}}</ref> Red Knots ''Calidris canutus'' and Dunlins ''Calidris alpina'' were found in radar studies to fly 5 km per hour faster in flocks than when they were flying alone.<ref name=newton/> |
|||
Birds fly at varying altitudes during migration. An expedition to [[Mount Everest|Mt. Everest]] found skeletons of [[Northern Pintail|Pintail]] and [[Black-tailed Godwit]] at 5000 m (16,400 ft) on the [[Khumbu Glacier]].<ref>{{cite journal|author=Geroudet, P.|year=1954|title=Des oiseaux migrateurs trouvés sur la glacier de Khumbu dans l'Himalaya.|journal=Nos Oiseaux|volume=22|page=254}}</ref> [[Bar-headed Goose|Bar-headed Geese]] have been seen flying over the highest peaks of the Himalayas above 8000 m (29000 ft) even when low passes of 3000 m (10000 ft) were nearby.<ref>{{cite journal|author=Swan, L. W.|year=1970|title=Goose of the Himalayas.|journal=Nat. Hist.|volume=79|issue=10|pages=68–75}}</ref> Seabirds fly low over water but gain altitude when crossing land, and the reverse pattern is seen in landbirds.<ref>{{cite book|author=Dorst, J.|year=1963|title=The migration of birds. |publisher=Houghton Mifflin Co., Boston. |page=476}}</ref><ref>{{cite journal|author=Eastwood, E. & G. C. Rider. |year=1965 |title=Some radar measurements of the altitude of bird flight.|journal=British Birds |volume=58|pages=393–426}}</ref> However most bird migration is in the range of 150 m (500 ft) to 600 m (2000 ft). Bird-hit aviation records from the United States show most collisions occur below 600 m (2000 ft) and almost none above 1800 m (6000 ft).<ref>{{cite journal|author=Williams, G. G.|year=1950|title=Weather and spring migration.|journal=Auk|volume=67|pages=52–65}}</ref> |
|||
Bird migration is not limited to birds that can fly. Most species of penguin migrate by swimming. These routes can cover over 1000 km. Blue Grouse ''Dendragapus obscurus'' perform altitudinal migration mostly by walking. Emus in Australia have been observed to undertake long-distance movements on foot during droughts.<ref name=newton/> |
|||
==Historical views== |
|||
Records of bird migration were made 3000 years ago by [[Hesiod]], [[Homer]], [[Herodotus]] and [[Aristotle]]. The Bible also notes migrations, as in the [[Book of Job]] (39:26), where the inquiry is made: "Doth the hawk fly by Thy wisdom and stretch her wings toward the south?" The author of Jeremiah (8:7) wrote: "The stork in the heavens knoweth her appointed time; and the turtledove, and the crane, and the swallow, observe the time of their coming." |
|||
Aristotle noted that cranes traveled from the steppes of [[Scythia]] to marshes at the headwaters of the [[Nile]]. [[Pliny the Elder]], in his ''[[Natural History (Pliny)|Historia Naturalis]]'', repeats Aristotle's observations. Aristotle however suggested that swallows and other birds hibernated. This belief persisted as late as 1878, when [[Elliott Coues]] listed the titles of no less than 182 papers dealing with the hibernation of swallows. It was not until early in the nineteenth century that migration as an explanation for the winter disappearance of birds from northern climes was accepted.<ref name=Lincoln>{{cite book|author=Lincoln, F. C.|year=1979|title=Migration of Birds.|publisher=Fish and Wildlife Service. ''Circular 16'.|url=http://www.archive.org/details/migrationofbirds00lincrich}}</ref> |
|||
==Long-distance migration== |
|||
[[Image:SwainsonThrush23.jpg|right|thumb|[[Swainson's Thrush]]]] |
|||
[[Image:Northern Pintail.jpg|right|thumb|[[Northern Pintail]]]] |
|||
The typical image of migration is of northern landbirds, such as [[swallow]]s and birds of prey, making long flights to the tropics. Many northern-breeding [[duck]]s, [[goose|geese]] and [[swan]]s are also long-distance migrants, but need only to move from their Arctic breeding grounds far enough south to escape frozen waters. Most Holarctic [[wildfowl]] species remain in the Northern Hemisphere, but in countries with milder climates. For example, the [[pink-footed goose]] migrates from [[Iceland]] to [[Great Britain|Britain]] and neighbouring countries. Migratory routes and wintering grounds are traditional and learned by young during their first migration with their parents. Some ducks, such as the [[Garganey]], move completely or partially into the tropics. |
|||
The same considerations about barriers and detours that apply to long-distance land-bird migration apply to water birds, but in reverse: a large area of land without bodies of water that offer feeding sites is a barrier to a water bird. Open sea may also be a barrier to a bird that feeds in coastal waters. Detours avoiding such barriers are observed: for example, [[Brent Goose|Brent Geese]] migrating from the [[Taymyr Peninsula]] to the [[Wadden Sea]] travel via the [[White Sea]] coast and the [[Baltic Sea]] rather than directly across the [[Arctic Ocean]] and northern [[Scandinavia]]. |
|||
[[Image:BartailedGodwit24.jpg|right|thumb|[[Bar-tailed Godwit]]]] |
|||
A similar situation occurs with [[wader]]s (called "shorebirds" in North America). Many species, such as [[Dunlin]] and [[Western Sandpiper]], undertake long movements from their Arctic breeding grounds to warmer locations in the same hemisphere, but others such as [[Semipalmated Sandpiper]] travel longer distances to the tropics in the Southern Hemisphere. Like the large and powerful wildfowl, the waders are strong fliers. This means that birds wintering in temperate regions have the capacity to make further shorter movements in the event of particularly inclement weather. |
|||
For some species of waders, migration success depends on the availability of certain key food resources at stopover points along the migration route. This gives the migrants an opportunity to "refuel" for the next leg of the voyage. Some examples of important stopover locations are the [[Bay of Fundy]] and [[Delaware River|Delaware Bay]]. |
|||
Some Bar-tailed Godwits have the longest known non-stop flight of any migrant, flying 11,000 km from [[Alaska]] to their [[New Zealand]] non-breeding areas.<ref>{{cite journal|title=Crossing the ultimate ecological barrier: evidence for an 11,000 km-long nonstop flight from Alaska to New Zealand and Eastern Australia by Bar-tailed Godwits.|author=Gill, Robert E. Jr., Theunis Piersma, Gary Hufford, Rene Servranckx, Adrian Riegen|journal=The Condor |year=2005 |volume=107|issue=1|pages=1–20|doi=10.1650/7613}}</ref> Prior to migration, 55 percent of their bodyweight is stored fat to fuel this uninterrupted journey. |
|||
[[Image:Arctic terns.jpg|thumb|right|[[Arctic Tern]]s]] |
|||
[[Seabird]] migration is similar in pattern to those of the waders and waterfowl. Some, such as the [[Black Guillemot]] and some [[gull]]s, are quite sedentary; others, such as most [[tern]]s and [[auk]]s breeding in the temperate northern hemisphere, move varying distances south in the northern winter. The [[Arctic Tern]] has the longest-distance migration of any bird, and sees more daylight than any other, moving from its Arctic breeding grounds to the Antarctic non-breeding areas. One Arctic Tern, [[Bird ringing|ringed]] (banded) as a chick on the [[Farne Islands]] off the [[Great Britain|British]] east coast, reached [[Melbourne]], [[Australia]] in just three months from fledging, a sea journey of over 22,000 km (14,000 miles). A few seabirds, such as [[Wilson's Petrel]] and [[Great Shearwater]], breed in the southern hemisphere and migrate north in the southern winter. Seabirds have the additional advantage of being able to feed during migration over open waters. |
|||
The most pelagic species, mainly in the 'tubenose' order [[Procellariiformes]], are great wanderers, and the [[albatross]]es of the southern oceans may circle the globe as they ride the "roaring forties" outside the breeding season. The tubenoses spread widely over large areas of open ocean, but congregate when food becomes available. Many are also among the longest-distance migrants; [[Sooty Shearwater]]s nesting on the [[Falkland Islands]] migrate 14,000 km (9,000 miles) between the breeding colony and the [[Atlantic Ocean|North Atlantic Ocean]] off [[Norway]]. Some [[Manx Shearwater]]s do this same journey in reverse. As they are long-lived birds, they may cover enormous distances during their lives; one record-breaking Manx Shearwater is calculated to have flown 8 million km (5 million miles) during its over-50 year lifespan. |
|||
[[Image:Vulture 19o05.jpg|right|thumb|[[Griffon Vulture]] soaring]] |
|||
Some large broad-winged birds rely on [[thermal|thermal columns]] of rising hot air to enable them to soar. These include many [[bird of prey|birds of prey]] such as [[vulture]]s, [[eagle]]s, and [[buzzard]]s, but also [[stork]]s. These birds migrate in the daytime. Migratory species in these groups have great difficulty crossing large bodies of water, since thermals only form over land, and these birds cannot maintain active flight for long distances. The Mediterranean and other seas present a major obstacle to soaring birds, which must cross at the narrowest points. Massive numbers of large [[Bird of prey|raptor]]s and storks pass through areas such as [[Gibraltar]], [[Falsterbo]], and the [[Bosphorus]] at migration times. More common species, such as the [[Honey Buzzard]], can be counted in hundreds of thousands in autumn. Other barriers, such as mountain ranges, can also cause funnelling, particularly of large diurnal migrants. This is a notable factor in the [[Central America]]n migratory bottleneck. |
|||
[[Image:Rubythroathummer65.jpg|thumb|right|[[Ruby-throated Hummingbird]]]] |
|||
Many of the smaller insectivorous birds including the [[warbler]]s, [[hummingbird]]s and [[Old World flycatcher|flycatcher]]s migrate large distances, usually at night. They land in the morning and may feed for a few days before resuming their migration. The birds are referred to as ''passage migrants'' in the regions where they occur for short durations between the origin and destination.<ref>{{cite journal|author=Schmaljohann, Heiko, Felix Liechti and Bruno Bruderer|year=2007|title=Songbird migration across the Sahara: the non-stop hypothesis rejected!|journal=Proc Biol Sci. |volume=274|issue=1610|pages=735–739|doi=10.1098/rspb.2006.0011|pmid=17254999|pmc=2197203}}</ref> |
|||
Nocturnal migrants minimize predation, avoid overheating, and feed during the day.<ref name=Lincoln/> One cost of nocturnal migration is the loss of sleep. Migrants may be able to alter their quality of sleep to compensate for the loss.<ref>{{cite journal|author=Rattenborg, N.C., Mandt, B.H., Obermeyer, W.H., Winsauer, P.J., Huber, R.|year=2004 |title= Migratory Sleeplessness in the White-Crowned Sparrow (''Zonotrichia leucophrys gambelii''). |journal=PLoS Biol. |volume=2|issue=7|page=e212|doi=10.1371/journal.pbio.0020212|pmid=15252455|pmc=449897}}</ref> |
|||
==Short-distance and altitudinal migration== |
|||
[[Image:Cedar Waxwing-27527-1.jpg|right|thumb|[[Cedar Waxwing]]]] |
|||
Many long-distance migrants appear to be genetically programmed to respond to changing day length. Species that move short distances, however, may not need such a timing mechanism, and may move in response to local weather conditions. |
|||
Thus mountain and moorland breeders, such as [[Wallcreeper]] and [[White-throated Dipper]], may move only altitudinally to escape the cold higher ground. Other species such as [[Merlin (bird)|Merlin]] and [[Skylark]] will move further to the coast or to a more southerly region. Species like the [[Chaffinch]] are not migratory in [[Great Britain|Britain]], but will move south or to [[Ireland]] in very cold weather. |
|||
Short-distance passerine migrants have two evolutionary origins. Those that have long-distance migrants in the same family, such as the [[Chiffchaff]], are species of southern hemisphere origins that have progressively shortened their return migration to stay in the northern hemisphere. |
|||
Species that have no long-distance migratory relatives, such as the [[waxwing]]s, are effectively moving in response to winter weather, rather than enhanced breeding opportunities. |
|||
[[Image:WoodlandKingfisher.jpg|right|thumb|[[Woodland Kingfisher]]]] |
|||
In the tropics there is little variation in the length of day throughout the year, and it is always warm enough for a food supply (although because of competition, there may not be enough food for every bird). Migration within the tropics has been far less studied than in the temperate zones. It was once assumed that tropical birds were mostly sedentary; however, altitudinal migration and other within-tropics movements appear to be surprisingly common (citation needed). Many tropical regions have wet and dry seasons, inducing some birds to migrate or wander widely to find food. Indeed, the [[monsoon]]s of [[India]] are preceded by the arrival of the [[Jacobin Cuckoo]], the "harbinger of the monsoon". Other examples include the [[Woodland Kingfisher]] of west [[Africa]] and many Australian birds. |
|||
There are a few species, notably [[cuckoo]]s, which are genuine long-distance migrants within the tropics. An example is the [[Lesser Cuckoo]], which breeds in India and spends the non-breeding season in Africa. Such examples help make the case that food supplies, not weather per se, drive migration patterns. |
|||
Altitudinal migration is common on mountains worldwide, such as in the [[Himalayas]] and the [[Andes]]. Quite often, altitudinal migration is combined with distance migration; for example, the Himalayan [[Kashmir Flycatcher]] and [[Pied Thrush]] both move as far south as the highlands of [[Sri Lanka]]. Altitudinal migration may even be important to birds living on relatively small islands, such as the Hawaiian Islands, which have high mountains. |
|||
==Irruptions and dispersal== |
|||
Sometimes circumstances such as a good breeding season followed by a food source failure the following year lead to irruptions in which large numbers of a species move far beyond the normal range. [[Bohemian Waxwing]] and [[Common Crossbill]]s show this unpredictable variation in annual numbers. |
|||
The temperate zones of the southern continents have extensive arid areas, particularly in Australia and western southern Africa, and weather-driven movements are common but not always predictable. A couple of weeks of heavy rain in one part or another of the usually dry centre of Australia, for example, causes dramatic plant and invertebrate growth, attracting birds from all directions. This can happen at any time of year, and, in any given area, may not happen again for a decade or more, depending on the frequency of |
|||
[[El Niño]] and [[La Niña]] periods. |
|||
[[Image:Rainbowbeeeater.jpg|right|thumb|[[Rainbow Bee-eater]]]] |
|||
Bird migration is primarily, but not entirely, a Northern Hemisphere phenomenon. In the Southern Hemisphere, seasonal migration tends to be much less obvious. There are several reasons for this. |
|||
First, the largely uninterrupted expanses of land mass or ocean tend not to funnel migrations into narrow and obvious pathways, making them less obvious to the human observer. Second, at least for terrestrial birds, climatic regions tend to fade into one another over a long distance rather than be entirely separate: this means that rather than make long trips over unsuitable habitat to reach particular destinations, migrant species can usually travel at a relaxed pace, feeding as they go. Short of banding studies it is often not obvious that the birds seen in any particular locality as the seasons change are in fact different members of the same species passing through, gradually working their way north or south. |
|||
Many species do in fact breed in the temperate southern hemisphere regions and winter further north in the tropics. The southern [[Africa]]n [[Greater Striped Swallow]], and the [[Australia]]n [[Satin Flycatcher]], [[Dollarbird]], and [[Rainbow Bee-eater]] for example, winters well north of their breeding range.<!-- |
|||
Those smaller species that migrate during the day tend to be those making movements that are relatively short and weather-driven, like the [[lark]]s and [[finch]]es, or that can feed on the wing, like [[swallow]]s and [[swift]]s.--> |
|||
==Physiology and control== |
|||
The control of migration, its timing and response are genetically controlled and appear to be a primitive trait that is present even in non-migratory species of birds. The ability to navigate and orient themselves during migration is a much more complex phenomenon that may include both endogenous programs as well as learning.<ref>{{cite journal|author=Helm B, Gwinner E |year=2006|title= Migratory Restlessness in an Equatorial Nonmigratory Bird. |journal=PLoS Biol. |volume=4|issue=4|page=e110 |doi=10.1371/journal.pbio.0040110|pmid=16555925|pmc=1420642}}</ref> |
|||
===Timing=== |
|||
The primary physiological cue for migration are the changes in the day length. These changes are also related to hormonal changes in the birds. |
|||
In the period before migration, many birds display higher activity or [[Zugunruhe]] ({{lang-de|migratory restlessness}}) as well as physiological changes such as increased fat deposition. The occurrence of Zugunruhe even in cage-raised birds with no environmental cues (e.g. shortening of day and falling temperature) has pointed to the role of circannual [[endogenous]] programs in controlling bird migrations. Caged birds display a preferential flight direction that corresponds with the migratory direction they would take in nature, even changing their preferential direction at roughly the same time their wild conspecifics change course. |
|||
In species where there is polygyny and with considerable sexual dimorphism, there is a tendency for males to return earlier to the breeding sites than their females. This is termed as protandry.<ref>{{cite journal|author=Diego Rubolini, Fernando Spina and Nicola Saino|year=2004|title=Protandry and sexual dimorphism in trans-Saharan migratory birds.|journal=Behavioral Ecology|volume=15|issue=4|pages=592–601|url=http://beheco.oxfordjournals.org/cgi/content/abstract/15/4/592|doi=10.1093/beheco/arh048}}</ref><ref>{{cite journal|author=Edwards, Darryl B.; Forbes, Mark R.|year=2007|title= Absence of protandry in the spring migration of a population of Song Sparrows Melospiza melodia.|journal=Ibis |volume=149|issue=4|pages=715–720|doi=10.1111/j.1474-919X.2007.00692.x}}</ref> |
|||
===Orientation and navigation=== |
|||
[[Image:Bar-tailed Godwit migration.jpg|thumb|300px|The routes of satellite tagged [[Bar-tailed Godwit]]s migrating north from [[New Zealand]]. This species has the longest known non-stop migration of any species, up to {{convert|10200|km|mi|-2|abbr=on}}.]] |
|||
Navigation is based on a variety of senses. Many birds have been shown to use a sun compass. Using the sun for direction involves the need for making compensation based on the time. Navigation has also been shown to be based on a combination of other abilities including the ability to detect magnetic fields ([[magnetoception]]), use visual landmarks as well as [[olfactory navigation|olfactory cues]].<ref name=walraffpigeon>{{cite book|author=Walraff, H. G. |year=2005|title= Avian Navigation: Pigeon Homing as a Paradigm.|publisher= Springer}}</ref> |
|||
Long distance migrants are believed to disperse as young birds and form attachments to potential breeding sites and to favourite wintering sites. Once the site attachment is made they show high site-fidelity, visiting the same wintering sites year after year.<ref>{{cite book|author=Ketterson, E.D. and V. Nolan Jr.|year=1990|chapter= Site attachment and site fidelity in migratory birds: experimental evidence from the field and analogies from neurobiology.|title=Bird Migration.|editor=E. Gwinner |publisher=Springer Verlag|pages=117–129 |url=http://www.indiana.edu/~kettlab/ellen/pubs/KettersonNolan1990.pdf |format=PDF}}</ref> |
|||
The ability of birds to navigate during migrations cannot be fully explained by endogenous programming, even with the help of responses to environmental cues. The ability to successfully perform long-distance migrations can probably only be fully explained with an accounting for the cognitive ability of the birds to recognize habitats and form mental maps. [[Satellite tracking (animal migration)|Satellite tracking]] of day migrating raptors such as Ospreys and Honey Buzzards has shown that older individuals are better at making corrections for wind drift.<ref>{{cite journal|author=Thorup, Kasper, Thomas Alerstam, Mikael Hake and Nils Kjelle |year=2003|title=Compensation for wind drift in migrating raptors is age dependent. |journal=Proc. R. Soc. Lond. B (Suppl.) |volume=270|pages=S8–S11|doi=10.1098/rsbl.2003.0014|pmid=12952622|pmc=1698035}}</ref> |
|||
As the circannual patterns indicate, there is a strong [[gene]]tic component to migration in terms of timing and route, but this may be modified by environmental influences. An interesting example where a change of migration route has occurred because of such a geographical barrier is the trend for some [[Blackcap]]s in central Europe to migrate west and winter in [[Great Britain|Britain]] rather than cross the [[Alps]]. |
|||
Migratory birds may use two [[Electromagnetism|electromagnetic]] tools to find their destinations: one that is entirely innate and another that relies on experience. A young bird on its first migration flies in the correct direction according to the Earth's [[magnetic field]], but does not know how far the journey will be. It does this through a [[radical pair mechanism]] whereby chemical reactions in special [[biological pigment|photo pigment]]s sensitive to [[Color#Physics|long wavelengths]] are affected by the field. Note that although this only works during daylight hours, it does not use the position of the sun in any way. At this stage the bird is similar to a [[boy scout]] with a compass but no map, until it grows accustomed to the journey and can put its other facilities to use. With experience they learn various landmarks and this "mapping" is done by [[magnetite]]s in the [[trigeminal system]], which tell the bird how strong the field is. Because birds migrate between northern and southern regions, the magnetic field strengths at different [[latitude]]s let it interpret the radical pair mechanism more accurately and let it know when it has reached its destination.<ref>{{cite journal|author=Wiltschko, W., U. Munro, H. Ford & R. Wiltschko|year=2006|title=Bird navigation: what type of information does the magnetite-based receiver provide?|journal=Proc. R. Soc. B|volume=273|pages=2815–20|doi=10.1098/rspb.2006.3651|pmid=17015316|issue=1603|pmc=1664630}}</ref> More recent research has found a neural connection between the eye and "Cluster N", the part of the forebrain that is active during migrational orientation, suggesting that birds may actually be able to ''see'' the magnetic field of the earth.<ref>{{cite journal|author=Heyers D, Manns M, Luksch H, Güntürkün O, Mouritsen H |year=2007|title= A Visual Pathway Links Brain Structures Active during Magnetic Compass Orientation in Migratory Birds. |journal=PLoS ONE|volume=2|issue=9|page=e937 |doi=10.1371/journal.pone.0000937|pmid=17895978|pmc=1976598}}</ref><ref>{{cite journal|author=Deutschlander, ME, Phillips, JB, Borland, SC |year=1999|title= The case for light-dependent magnetic orientation in animals.|journal=J.Exp. Biol. |volume=202|pages=891–908 |url=http://jeb.biologists.org/cgi/reprint/202/8/891 |format=PDF|issue=8}}</ref> |
|||
===Vagrancy=== |
|||
Migrating birds can lose their way and appear outside their normal ranges. This can be due to flying past their destinations as in the "spring overshoot"{{anchor|overshoot}} in which birds returning to their breeding areas overshoot and end up further north than intended. [[Reverse migration]], where the genetic programming of young birds fails to work properly, can lead to great rarities turning up as vagrants thousands of kilometres out of range. Certain areas, because of their location, have become famous as watchpoints for migrating birds. Examples are the [[Point Pelee National Park]] in Canada, and [[Spurn]] in [[England]]. [[Drift migration]] of birds blown off course by the wind can result in "falls" of large numbers of migrants at coastal sites. |
|||
===Migration conditioning=== |
|||
It has been possible to teach a migration route to a flock of birds, for example in re-introduction schemes. After a trial with [[Canada Goose|Canada Geese]], [[microlight]] aircraft were used in the US to teach safe migration routes to reintroduced [[Whooping Crane]]s.<ref>{{cite web|url=http://www.operationmigration.org/index.html|title=Operation migration}}</ref><ref>{{cite web|url=http://dnr.wi.gov/org/land/er/birds/wcrane/wcraneplan.htm |title=Whooping Crane Management Plan (Wisconsin)}}</ref> |
|||
==Adaptations== |
|||
Birds need to alter their metabolism in order to meet the demands of migration. The storage of energy through the accumulation of fat and the control of sleep in nocturnal migrants require special physiological adaptations. In addition, the feathers of a bird suffer from wear-and-tear and require to be molted. The timing of this molt - usually once a year but sometimes two - varies with some species molting prior to moving to their winter grounds and others molting prior to returning to their breeding grounds.<ref>{{cite book|editor=Greenberg R & Marra PP|page=94|title=Birds of two worlds: the ecology and evolution of migration|publisher=Johns Hopkins University Press|year= 2005|isbn=0801881072|chapter=Ecology and Demography of East-West Differences in Molt Scheduling of Neotropical Migrant Passerines|author=Rohwer S; Butler LK & DR Froehlich }}</ref><ref>{{cite journal|title=Adaptations to migration in birds: behavioural strategies, morphology and scaling effects|journal=Phil. Trans. R. Soc. B |year=2008|volume=363|pages=287–299|doi=10.1098/rstb.2007.2140|pmid=17638691|last1=Hedenström|first1=A|issue=1490|pmc=2606751}}</ref> Apart from physiological adaptations, migration sometimes requires behavioural changes such as flying in flocks to reduce the energy used in migration or the risk of predation.<ref>{{cite journal|author=Weber, Jean-Michel|title=The physiology of long-distance migration: extending the limits of endurance metabolism|journal=J. Exp. Biol.|year=2009|volume=212|pages=593–597|doi=10.1242/jeb.015024|pmid=19218508|issue=Pt 5 }}</ref> |
|||
==Evolutionary and ecological factors== |
|||
Whether a particular species migrates depends on a number of factors. The climate of the breeding area is important, and few species can cope with the harsh winters of inland [[Canada]] or northern [[Eurasia]]. Thus the partially migratory [[Common Blackbird|Blackbird]] ''Turdus merula'' is migratory in [[Scandinavia]], but not in the milder climate of southern Europe. The nature of the staple food is also significant. Most specialist insect eaters outside the tropics are long-distance migrants, and have little choice but to head south in winter. |
|||
Sometimes the factors are finely balanced. The [[Whinchat]] ''Saxicola rubetra'' of Europe and the [[Siberian Stonechat]] ''Saxicola maura'' of Asia are long-distance migrants wintering in the tropics, whereas their close relative, the [[European Stonechat]] ''Saxicola rubicola'' is a [[resident bird]] in most of its range, and moves only short distances from the colder north and east. A possible factor here is that the resident species can often raise an extra brood. |
|||
Recent research suggests that long-distance passerine migrants are of [[South America]]n and [[Africa]]n, rather than [[northern hemisphere]], [[evolution]]ary origins. They are effectively southern species coming north to breed rather than northern species going south to winter. |
|||
Theoretical analyses, summarized by Alerstam (2001), show that detours that increase flight distance by up to 20% will often be adaptive on [[aerodynamics|aerodynamic]] grounds - a bird that loads itself with food to cross a long barrier flies less efficiently. However some species show circuitous migratory routes that reflect historical range expansions and are far from optimal in ecological terms. An example is the migration of continental populations of [[Swainson's Thrush]], which fly far east across [[North America]] before turning south via [[Florida]] to reach northern [[South America]]; this route is believed to be the consequence of a range expansion that occurred about 10,000 years ago. Detours may also be caused by differential wind conditions, predation risk, or other factors. |
|||
===Climate change=== |
|||
Large scale climatic changes, as have been experienced in the past, are expected to have an effect on the timing of migration. Studies have shown a variety of effects including timing changes in migration, breeding<ref>{{cite journal|author=Jenni L. & Kery M.|year=2003|title= Timing of autumn bird migration under climate change: advances in long-distance migrants, delays in short-distance migrants. |journal=Proceedings of the Royal Society of London B |volume=270|page=1467}}</ref> as well as population variations.<ref>{{cite journal |
|||
|doi=10.1038/nature04539 |
|||
|issn = 0028-0836 |
|||
|volume=441 |
|||
|issue=7089 |
|||
|pages=81–83 |
|||
|last=Both |
|||
|first=Christiaan |
|||
|coauthors=Sandra Bouwhuis, C. M. Lessells, Marcel E. Visser |
|||
|title=Climate change and population declines in a long-distance migratory bird |
|||
|journal=Nature |
|||
|date=2006-05-04 |
|||
|pmid=16672969 |
|||
}}</ref><ref>{{cite book|author=Wormworth, J. & K. Mallon |year=2006|title= Bird Species and Climate Change: The Global Status Report version 1.0. |publisher=WWF|url=http://www.panda.org/about_wwf/what_we_do/climate_change/problems/impacts/species/cc_and_birds/index.cfm }}</ref> |
|||
==Ecological effects== |
|||
The migration of birds also aids the movement of other species, including those of [[ectoparasite]]s such as ticks and lice,<ref>{{cite journal|author=Smith RP Jr, Rand PW, Lacombe EH, Morris SR, Holmes DW, Caporale DA|year=1996|title= Role of bird migration in the long-distance dispersal of ''Ixodes dammini'', the vector of Lyme disease. |journal=J. Infect. Dis.|issue=1|pages=221–4|pmid=8656000}}</ref> which in turn may carry micro-organisms including those of concern to human health. Considerable interest has been taken due to the global spread of [[avian influenza]], however migrant birds have not been found to be a special risk, with import of pet and domestic birds being a greater threat.<ref>{{cite journal|author=Rappole, J.H., Hubálek, Zdenek |year=2006|title= Birds and Influenza H5N1 Virus Movement to and within North America. |journal=Emerging Infectious Diseases|volume=12|page=10|url=http://hdl.handle.net/10088/875}}</ref> Some viruses that are maintained in birds without lethal effects, such as the [[West Nile Virus]] may however be spread by migrating birds.<ref>{{cite journal|author=Rappole, J.H., Derrickson, S.R., Hubalek, Z. |year=2000|title= Migratory Birds and Spread of West Nile Virus in the Western Hemisphere. |journal=Emerging Infectious Diseases |volume=6|issue=4|pages=319–328|url=http://hdl.handle.net/10088/364|doi=10.3201/eid0604.000401|pmid=10905964|pmc=2640881}}</ref> Birds may also have a role in the dispersal of propagules of plants and plankton.<ref>{{cite journal|author=Figuerola, O. and A. J. Green |year=2002|title= Dispersal of aquatic organisms by waterbirds: a review of past research and priorities for future studies.|journal= Freshwater Biology |volume=47|issue=3|pages=483–494|doi=10.1046/j.1365-2427.2002.00829.x}}</ref><ref>{{cite journal|author=Cruden, R. W.|year=1966|title=Birds as Agents of Long-Distance Dispersal for Disjunct Plant Groups of the Temperate Western Hemisphere.|journal= Evolution |volume=20|issue=4|pages=517–532|doi=10.2307/2406587|url=http://jstor.org/stable/2406587|publisher=Evolution, Vol. 20, No. 4}}</ref> |
|||
Some predators take advantage of the concentration of birds during migration. [[Greater Noctule bat]]s feed on nocturnal migrating passerines.<ref name=bats/> Some birds of prey specialize on migrating waders.<ref>{{cite journal|journal=Proc. R. Soc. Lond. B|year=2004|volume=271|pages=1263–1269 1263|doi=10.1098/rspb.2004.2713|title=Western sandpipers have altered migration tactics as peregrine falcon populations have recovered|author=Ronald C. Ydenberg, Robert W. Butler, David B. Lank, Barry D. Smith and John Ireland|url=http://www.sfu.ca/biology/wildberg/ydenbergetal2004PRSB.pdf|pmid=15306350|issue=1545|pmc=1691718}}</ref> |
|||
==Study techniques== |
|||
Early studies on the timing of migration began in 1749 in Finland, with Johannes Leche of Turku collecting the dates of arrivals of spring migrants.<ref>{{cite journal|title=Citizens, science and bird conservation|first=Jeremy J. D.|last=Greenwood|journal=J. Ornithol .|year=2007|volume=148|issue=Suppl 1|pages=S77–S124|doi=10.1007/s10336-007-0239-9}}</ref> |
|||
Bird migration routes have been studied by a variety of techniques of which [[Bird ringing|ringing]] is the oldest. Color marking and use of [[radar]], [[GPS satellite|satellite tracking]] are some of the other techniques. |
|||
Stable isotopes of hydrogen, oxygen, carbon, nitrogen, and sulphur have also been used to establish avian migratory connectivity between wintering sites and breeding grounds. Stable isotopic methods to establish migratory linkage rely on spatial isotopic differences in bird diet that are incorporated into inert tissues like feathers, or into growing tissues such as claws and muscle or blood.<ref>{{cite journal|author=Keith Hobson, Leonard Wassenaar |title=Linking breeding and wintering grounds of neotropical migrant songbirds using stable hydrogen isotopic analysis of feathers|journal=Oecologia|year=1997|volume=109|pages=142–148|doi=10.1007/s004420050068}}</ref><ref>{{cite journal|author=Gabriel Bowen, Leonard Wassenaar, Keith Hobson|title=Global application of stable hydrogen and oxygen isotopes to wildlife forensics|journal=Oecologia|year=2005|volume=143|pages=337–348|doi=10.1007/s00442-004-1813-y|pmid=15726429|issue=3}}</ref> |
|||
An approach to identify migration intensity makes use of upward pointing microphones to record the nocturnal contact calls of flocks flying overhead. These are then analyzed in a laboratory to measure time, frequency and species.<ref>{{cite journal|author=Farnsworth, A., Gauthreaux, S.A., and van Blaricom, D.|year=2004|title= A comparison of nocturnal call counts of migrating birds and reflectivity measurements on Doppler radar. |journal=Journal of Avian Biology |volume=35|pages=365–369|url=http://www.andrewfarnsworth.com/PDFs/JAB3180.pdf|format=PDF|doi=10.1111/j.0908-8857.2004.03180.x}}</ref> |
|||
[[Image:EmlenFunnel.svg|thumb|[[Emlen funnel]]]] |
|||
An older technique to quantify migration involves observing the face of the moon towards full moon and counting the silhouettes of flocks of birds as they fly at night.<ref>{{cite book|author=Liechti, F. |year=1996|title= Instructions to count nocturnal bird migration by watching the full moon. |publisher=[[Sempach Bird Observatory|Schweizerische Vogelwarte]], CH-6204 Sempach, Switzerland}}</ref><ref>{{cite journal|author=Lowery, G.H. |year=1951|title=A quantitative study of the nocturnal migration of birds.|journal=University Kan. Pub. Mus. Nat. Hist.|volume=3|pages=361–472|url=http://www.archive.org/stream/universityofkans195103univ#page/n373/mode/1up}}</ref> |
|||
Orientation behaviour studies have been traditionally carried out using variants of a setup known as the '''Emlen funnel''', which consists of a circular cage with the top covered by glass or wire-screen so that either the sky is visible or the setup is placed in a planetarium or with other controls on environmental cues. The orientation behaviour of the bird inside the cage is studied quantitatively using the distribution of marks that the bird leaves on the walls of the cage.<ref>{{cite journal|author=Emlen, S. T. and Emlen, J. T.|year=1966|title= A technique for recording migratory orientation of captive birds.|journal=Auk|volume=83|pages=361–367}}</ref> Other approaches used in pigeon homing studies make use of the direction in which the bird vanishes on the horizon. |
|||
==Threats and conservation== |
|||
Human activities have threatened many migratory bird species.The distances involved in bird migration mean that they often cross political boundaries of countries and conservation measures require international cooperation. Several international treaties have been signed to protect migratory species including the [[Migratory Bird Treaty Act]] of 1918 of the US<ref>{{cite web|url=http://www.law.cornell.edu/uscode/16/ch7.html |title=Migratory bird Treaty 16 USC 703-711; 40 Stat. 755}}</ref> and the African-Eurasian Migratory Waterbird Agreement.<ref>{{cite web|url=http://www.unep-aewa.org/documents/index.htm |title=African-Eurasian Migratory Waterbird Agreement}}</ref> |
|||
The concentration of birds during migration can put species at risk. Some spectacular migrants have already gone extinct, the most notable being the [[Passenger Pigeon]] (''Ectopistes migratorius''). During migration the flocks were a mile (1.6 km) wide and 300 miles (500 km) long, taking several days to pass and containing up to a billion birds. |
|||
Other significant areas include stop-over sites between the wintering and breeding territories.<ref>{{cite journal|author=Shimazaki, Hiroto; Masayuki Tamura and Hiroyoshi Higuchi |year=2004|title= Migration routes and important stopover sites of endangered oriental white storks (''Ciconia boyciana'') as revealed by satellite tracking. Mem.|journal= Natl Inst. Polar Res., Spec. Issue|volume=58|pages=162–178|url=http://www.nipr.ac.jp/~penguin/oogataHP/pdfarticles/16p162-178.pdf |format=PDF}}</ref> A capture-recapture study of passerine migrants with high fidelity for breeding and wintering sites did not show similar strict association with stop-over sites.<ref>{{cite journal|author=Catry, P., Encarnacao, V., Araujo, A., Fearon, P., Fearon, A., Armelin, M. & Delaloye, P.|year=2004|title= Are long-distance migrant passerines faithful to their stopover sites? |journal=Journal of Avian Biology |volume= 35|pages=170–181|doi=10.1111/j.0908-8857.2004.03112.x}}</ref> |
|||
[[Hunting]] along the migratory route can also take a heavy toll. The populations of [[Siberian Crane]]s that wintered in [[India]] declined due to hunting along the route, particularly in [[Afghanistan]] and [[Central Asia]]. Birds were last seen in their favourite wintering grounds in [[Keoladeo National Park]] in 2002.<ref>{{cite web|url=http://www.savingcranes.org/species/siberian.cfm |title=Siberian Crane fact sheet}}</ref> |
|||
Structures such as power lines, wind farms and offshore oil-rigs have also been known to affect migratory birds.<ref>{{cite web|url=http://www.fws.gov/birds/mortality-fact-sheet.pdf |format=PDF|title=Fish and Wildlife Service- Bird Mortality Fact sheet}}</ref> Habitat destruction by land use changes is the biggest threat, and shallow wetlands that are stopover and wintering sites for migratory birds are particularly threatened by draining and reclamation for human use. |
|||
==See also== |
|||
*[[Winged Migration]], 2001 documentary film |
|||
==References==<!-- CurrBiol18:188. --> |
|||
{{reflist|2}} |
|||
==Further reading== |
|||
*Alerstam, T. (2001). Detours in bird migration. ''Journal of Theoretical Biology'', 209, 319-331. ([http://orn-lab.ekol.lu.se/birdmigration/documents/pdf_articles/meglu74.pdf PDF Orn-lab.ekol.lu.se]) |
|||
*Berthold, Peter (2001) Bird Migration: A General Survey. Second Edition. Oxford University Press. ISBN 0-19-850787-9 |
|||
*Dingle, Hugh. Migration: The Biology of Life on The Move. Oxford University Press, 1996. |
|||
*[[Scott Weidensaul|Weidensaul, Scott]]. Living On the Wind: Across the Hemisphere With Migratory Birds. Douglas & McIntyre, 1999. |
|||
*[http://publishing.royalsociety.org/annual-cycle Dedicated issue of ''Philosophical Transactions B'' on Adaptation to the Annual Cycle. Some articles are freely available.] |
|||
*Hobson, Keith and Wassenaar, Leonard (2008) Tracking Animal Migration with Stable Isotopes. Academic Press. ISBN 978-0-12-373867-7 |
|||
==External links== |
|||
*[http://www.olangowildlifesanctuary.org/ Route of East Asian Migratory Flyaway] Olango Wildlife Sanctuary as a refuelling station of migratory birds |
|||
*[http://www.migraction.net/ Migraction.net] - Interactive database with real-time information on bird migration |
|||
*[http://orn-lab.ekol.lu.se/birdmigration Migration Ecology Group, Lund University, Sweden] |
|||
*[http://www.migrate.ou.edu Migrate.ou.edu] - Migration Interest Group: Research Applied Toward Education, USA |
|||
*[http://www.trektellen.nl/default.asp?taal=2 Trektellen.nl ] - Migration counts and ringing records The Netherlands, Belgium, Great Britain, France, Germany, Spain and Portugal |
|||
*[http://www.bsc-eoc.org/national/cmmn.html Canadian Migration Monitoring Network (Co-ordinates bird migration monitoring stations across Canada)] |
|||
*[http://www.sciencedaily.com/news/plants_animals/birds/ Bird Research by Science Daily]- includes several articles on bird migration |
|||
*[http://www.nature.org/initiatives/programs/birds/ The Nature Conservancy's Migratory Bird Program] |
|||
* [http://www.scq.ubc.ca/?p=173 The Compasses of Birds] - a review from the Science Creative Quarterly |
|||
* [http://www.bbc.co.uk/nature/animals/birds/supergoose/index.shtml BBC Supergoose] - satellite tagging of light-bellied brent geese |
|||
* [http://www.ospreyworld.com/soaring/index.html Soaring with Fidel] - follow the annual migration of ospreys from Cape Cod to Cuba to Venezuela |
|||
* [http://news.nationalgeographic.com/news/2002/09/0926_020927_birdmigration.html Birder's Journal: A Morning With Migrants] Nationalgeographic.com |
|||
* [http://www.swild.ch/publi/Bontadina_FunEco2003.pdf Bat predation on migrating birds] |
|||
* [http://cgi.turnerlearning.com/efts/species.970730/migover.html Bird migration overview] A general overview from cgi.turnerlearning.com |
|||
* [http://www.groms.de/ Global Register of Migratory Species] - features not only birds, but other migratory vertebrates such as fishes |
|||
{{collective animal behaviour}} |
|||
{{Birds}} |
|||
{{DEFAULTSORT:Bird Migration}} |
|||
[[Category:Ornithology]] |
|||
[[Category:Bird flight]] |
|||
[[Category:Bird terminology]] |
|||
{{Link GA|uk}} |
|||
{{Link FA|he}} |
|||
[[ca:Au migratòria]] |
|||
[[cy:Aderyn mudol]] |
|||
[[da:Fugletræk]] |
|||
[[de:Vogelzug]] |
|||
[[es:Migración de las aves]] |
|||
[[eo:Birdomigrado]] |
|||
[[fr:Migration des oiseaux]] |
|||
[[gd:Eòin turais no Eòin siubhail]] |
|||
[[ko:철새]] |
|||
[[hi:पक्षियों का प्रव्रजन]] |
|||
[[hr:Seoba ptica]] |
|||
[[id:Migrasi burung]] |
|||
[[is:Farfugl]] |
|||
[[it:Uccelli migratori]] |
|||
[[he:נדידת עופות]] |
|||
[[ka:ფრინველთა მიმოფრენა]] |
|||
[[lt:Paukščių migracijos]] |
|||
[[nl:Vogeltrek]] |
|||
[[ja:渡り鳥]] |
|||
[[no:Fugletrekk]] |
|||
[[nn:Fugletrekk]] |
|||
[[pl:Wędrówki ptaków]] |
|||
[[pt:Ave migratória]] |
|||
[[ro:Pasăre migratoare]] |
|||
[[ru:Миграция птиц]] |
|||
[[sl:Ptica selivka]] |
|||
[[fi:Muuttolintu]] |
|||
[[sv:Flyttfågel]] |
|||
[[ta:பறவைகள் புலப்பெயர்வு]] |
|||
[[tr:Göçmen kuşlar]] |
|||
[[uk:Міграція птахів]] |
|||
[[zh:鸟类迁徙]] |
Revision as of 15:15, 7 September 2011
Auston was here