80-439: 4, see text Godwits are a group of four large, long-billed, long-legged and strongly migratory waders of the bird genus Limosa . Their long bills allow them to probe deeply in the sand for aquatic worms and molluscs . In their winter range, they flock together where food is plentiful. They frequent tidal shorelines, breeding in northern climates in summer and migrating south in winter. A female bar-tailed godwit made
160-447: A Numenius species, was a discrepancy in this general trend. L. gypsorum was only 63% of the way between a typical reptilian ratio and that of modern birds. However, this may be explainable if the endocast was distorted, as it had been previously depicted in the past by Deschaseaux, who is described by Larsson as calling the endocast "slightly anteroposteriorly sheared and laterally compressed." Bird migration Bird migration
240-498: A rail , being placed in the monotypic genus Montirallus by some (Olson, 1985). Certainly, curlews and godwits are rather ancient and in some respects primitive lineages of scolopacids, further complicating the assignment of such possibly basal forms. In a 2001 study comparing the ratios cerebrum to brain volumes in various dinosaur species, Hans C. E. Larsson found that more derived dinosaurs generally had proportionally more voluminous cerebrum. Limosa gypsorum , then regarded as
320-498: A white stork was found in the German state of Mecklenburg with an arrow made from central African hardwood, which provided some of the earliest evidence of long-distance stork migration. This bird was referred to as a Pfeilstorch , German for "Arrow stork". Since then, around 25 Pfeilstörche have been documented. Migration is the regular seasonal movement, often north and south, undertaken by many species of birds. Migration
400-1284: A barrier, and detours avoiding such barriers are observed. For example, brent geese Branta bernicla bernicla migrating between the Taymyr Peninsula and the Wadden Sea travel via low-lying coastal feeding-areas on the White Sea and the Baltic Sea rather than directly across the Arctic Ocean and the Scandinavian mainland. Great snipes make non-stop flights of 4,000–7,000 km, lasting 60–90 h, during which they change their average cruising heights from 2,000 m (above sea level) at night to around 4,000 m during daytime. A similar situation occurs with waders (called shorebirds in North America). Many species, such as dunlin Calidris alpina and western sandpiper Calidris mauri , undertake long movements from their Arctic breeding grounds to warmer locations in
480-642: A chick on the Farne Islands in Northumberland off the British east coast, reached Melbourne , Australia in just three months from fledging, a sea journey of over 22,000 km (12,000 nmi), while another also from the Farne Islands with a light level geolocator tag 'G82' covered a staggering 96,000 km (52,000 nmi) in just 10 months from the end of one breeding season to
560-473: A definition similar to "all theropods closer to birds than to Deinonychus ", with Troodon being sometimes added as a second external specifier in case it is closer to birds than to Deinonychus . Avialae is also occasionally defined as an apomorphy-based clade (that is, one based on physical characteristics). Jacques Gauthier , who named Avialae in 1986, re-defined it in 2001 as all dinosaurs that possessed feathered wings used in flapping flight , and
640-423: A flight of 29,000 km (18,000 mi), flying 11,680 kilometres (7,260 mi) of it without stopping. In 2020 a male bar-tailed godwit flew about 12,200 kilometres (7,600 mi) non-stop in its migration from Alaska to New Zealand, previously a record for avian non-stop flight. In October 2022, a 5 month old, male bar-tailed godwit was tracked from Alaska to Tasmania , a trip that took 11 days, and recorded
720-442: A group called Paraves . Some basal members of Deinonychosauria, such as Microraptor , have features which may have enabled them to glide or fly. The most basal deinonychosaurs were very small. This evidence raises the possibility that the ancestor of all paravians may have been arboreal , have been able to glide, or both. Unlike Archaeopteryx and the non-avialan feathered dinosaurs, who primarily ate meat, studies suggest that
800-487: A man's story about swallows being found in a chalk cliff collapse "while he was a schoolboy at Brighthelmstone", though the man denied being an eyewitness. However, he writes that "as to swallows being found in a torpid state during the winter in the Isle of Wight or any part of this country, I never heard any such account worth attending to", and that if early swallows "happen to find frost and snow they immediately withdraw for
880-465: A non-stop flight of 8,400 miles (13,500 km). The godwits can be distinguished from the curlews by their straight or slightly upturned bills, and from the dowitchers by their longer legs. The winter plumages are fairly drab, but three species have reddish underparts when breeding. The females are appreciably larger than the males. Godwits were once a popular British dish. Sir Thomas Browne writing in about 1682 noted that godwits "were accounted
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#1732791317114960-406: A sister group, the order Crocodilia , contain the only living representatives of the reptile clade Archosauria . During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica . However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, and
1040-717: A time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (one male with many females) or, rarely, polyandrous (one female with many males). Birds produce offspring by laying eggs which are fertilised through sexual reproduction . They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching. Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs, meat, and feathers. Songbirds , parrots, and other species are popular as pets. Guano (bird excrement)
1120-414: A time—a circumstance this much more in favour of hiding than migration", since he doubts they would "return for a week or two to warmer latitudes". Only at the end of the eighteenth century was migration accepted as an explanation for the winter disappearance of birds from northern climes. Thomas Bewick 's A History of British Birds (Volume 1, 1797) mentions a report from "a very intelligent master of
1200-468: A timing mechanism, instead moving in response to local weather conditions. Thus mountain and moorland breeders, such as wallcreeper Tichodroma muraria and white-throated dipper Cinclus cinclus , may move only altitudinally to escape the cold higher ground. Other species such as merlin Falco columbarius and Eurasian skylark Alauda arvensis move further, to the coast or towards the south. Species like
1280-560: A vessel" who, "between the islands of Menorca and Majorca , saw great numbers of Swallows flying northward", and states the situation in Britain as follows: Swallows frequently roost at night, after they begin to congregate, by the sides of rivers and pools, from which circumstance it has been erroneously supposed that they retire into the water. Bewick then describes an experiment that succeeded in keeping swallows alive in Britain for several years, where they remained warm and dry through
1360-627: Is a much more complex phenomenon that may include both endogenous programs as well as learning. The primary physiological cue for migration is the changes in the day length. These changes are related to hormonal changes in the birds. In the period before migration, many birds display higher activity or Zugunruhe ( German : migratory restlessness ), first described by Johann Friedrich Naumann in 1795, 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
1440-488: Is a seasonal movement of birds between breeding and wintering grounds that occurs twice a year. It is typically from north to south or from south to north. Migration is inherently risky, due to predation and mortality. The Arctic tern holds the long-distance migration record for birds, travelling between Arctic breeding grounds and the Antarctic each year. Some species of tubenoses , such as albatrosses , circle
1520-483: Is alterable with selective breeding. Many migration routes of long-distance migratory birds are circuitous due to evolutionary history: the breeding range of Northern wheatears Oenanthe oenanthe has expanded to cover the entire Northern Hemisphere, but the species still migrates up to 14,500 km to reach ancestral wintering grounds in sub-Saharan Africa rather than establish new wintering grounds closer to breeding areas. A migration route often does not follow
1600-576: Is an example of leap-frog migration . 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 the order. Within a population, it is common for different ages and/or sexes to have different patterns of timing and distance. Female chaffinches Fringilla coelebs in Eastern Fennoscandia migrate earlier in
1680-540: Is called ornithology . Birds are feathered theropod dinosaurs and constitute the only known living dinosaurs . Likewise, birds are considered reptiles in the modern cladistic sense of the term, and their closest living relatives are the crocodilians . Birds are descendants of the primitive avialans (whose members include Archaeopteryx ) which first appeared during the Late Jurassic . According to recent estimates, modern birds ( Neornithes ) evolved in
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#17327913171141760-695: 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. Red knots Calidris canutus and dunlins Calidris alpina were found in radar studies to fly 5 km/h (2.5 kn) faster in flocks than when they were flying alone. Birds fly at varying altitudes during migration. An expedition to Mt. Everest found skeletons of northern pintail Anas acuta and black-tailed godwit Limosa limosa at 5,000 m (16,000 ft) on
1840-665: Is evidence that this enables the migrants to obtain more of their preferred foods such as fruits. Altitudinal migration is common on mountains worldwide, such as in the Himalayas and the Andes . Dusky grouse in Colorado migrate less than a kilometer away from their summer grounds to winter sites which may be higher or lower by about 400 m in altitude than the summer sites. Many bird species in arid regions across southern Australia are nomadic; they follow water and food supply around
1920-429: Is harvested for use as a fertiliser. Birds figure throughout human culture. About 120 to 130 species have become extinct due to human activity since the 17th century, and hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry. The first classification of birds
2000-508: 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. 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
2080-602: Is known from the Monterey Formation (Late Miocene , approx. 6 mya ) of Lompoc , United States. Limosa lacrimosa is known from the Early Pliocene of Western Mongolia ( Kurochkin , 1985). Limosa gypsorum of the Late Eocene ( Montmartre Formation , some 35 mya) of France may have actually been a curlew or some bird ancestral to both curlews and godwits (and possibly other Scolopacidae ), or even
2160-499: Is marked by its annual seasonality and movement between breeding and non-breeding areas. Nonmigratory bird movements include those made in response to environmental changes including 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). Non-migratory birds are said to be resident or sedentary. Approximately 1,800 of
2240-503: Is not considered a direct ancestor of birds, though it is possibly closely related to the true ancestor. Over 40% of key traits found in modern birds evolved during the 60 million year transition from the earliest bird-line archosaurs to the first maniraptoromorphs , i.e. the first dinosaurs closer to living birds than to Tyrannosaurus rex . The loss of osteoderms otherwise common in archosaurs and acquisition of primitive feathers might have occurred early during this phase. After
2320-516: Is synonymous to Avifilopluma. † Scansoriopterygidae † Eosinopteryx † Jinfengopteryx † Aurornis † Dromaeosauridae † Troodontidae Avialae Based on fossil and biological evidence, most scientists accept that birds are a specialised subgroup of theropod dinosaurs and, more specifically, members of Maniraptora , a group of theropods which includes dromaeosaurids and oviraptorosaurs , among others. As scientists have discovered more theropods closely related to birds,
2400-535: Is used by many scientists including adherents to the PhyloCode . Gauthier defined Aves to include only the crown group of the set of modern birds. This was done by excluding most groups known only from fossils , and assigning them, instead, to the broader group Avialae, on the principle that a clade based on extant species should be limited to those extant species and their closest extinct relatives. Gauthier and de Queiroz identified four different definitions for
2480-477: The Bay of Fundy and Delaware Bay . Some bar-tailed godwits Limosa lapponica baueri have the longest known non-stop flight of any migrant, flying 11,000 km from Alaska to their New Zealand non-breeding areas. Prior to migration, 55 percent of their bodyweight is stored as fat to fuel this uninterrupted journey. Seabird migration is similar in pattern to those of the waders and waterfowl. Some, such as
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2560-711: The Bosphorus at migration times. More common species, such as the European honey buzzard Pernis apivorus , can be counted in hundreds of thousands in autumn. Other barriers, such as mountain ranges, can cause funnelling, particularly of large diurnal migrants, as in the Central American migratory bottleneck. The Batumi bottleneck in the Caucasus is one of the heaviest migratory funnels on earth, created when hundreds of thousands of soaring birds avoid flying over
2640-531: The Khumbu Glacier . Bar-headed geese Anser indicus have been recorded by GPS flying at up to 6,540 m (21,460 ft) while crossing the Himalayas, at the same time engaging in the highest rates of climb to altitude for any bird. Anecdotal reports of them flying much higher have yet to be corroborated with any direct evidence. Seabirds fly low over water but gain altitude when crossing land, and
2720-722: The Late Cretaceous and diversified dramatically around the time of the Cretaceous–Paleogene extinction event 66 million years ago, which killed off the pterosaurs and all non- ornithuran dinosaurs. Many social species preserve knowledge across generations ( culture ). Birds are social, communicating with visual signals, calls, and songs , and participating in such behaviour as cooperative breeding and hunting, flocking , and mobbing of predators. The vast majority of bird species are socially (but not necessarily sexually) monogamous , usually for one breeding season at
2800-669: The Tiaojishan Formation of China, which has been dated to the late Jurassic period ( Oxfordian stage), about 160 million years ago. The avialan species from this time period include Anchiornis huxleyi , Xiaotingia zhengi , and Aurornis xui . The well-known probable early avialan, Archaeopteryx , dates from slightly later Jurassic rocks (about 155 million years old) from Germany . Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds but were later lost during bird evolution. These features include enlarged claws on
2880-515: The black guillemot Cepphus grylle and some gulls , are quite sedentary; others, such as most terns and auks breeding in the temperate northern hemisphere, move varying distances south in the northern winter. The Arctic tern Sterna paradisaea 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, ringed (banded) as
2960-798: The dark-eyed junco migrates from subarctic and arctic climates to the contiguous United States and the American goldfinch from taiga to wintering grounds extending from the American South northwestward to Western Oregon . Some ducks, such as the garganey Anas querquedula , move completely or partially into the tropics. The European pied flycatcher Ficedula hypoleuca follows this migratory trend, breeding in Asia and Europe and wintering in Africa. Migration routes and wintering grounds are both genetically and traditionally determined depending on
3040-476: The laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart , and a strong yet lightweight skeleton . Birds live worldwide and range in size from the 5.5 cm (2.2 in) bee hummingbird to the 2.8 m (9 ft 2 in) common ostrich . There are over 11,000 living species and they are split into 44 orders . More than half are passerine or "perching" birds. Birds have wings whose development varies according to species;
3120-483: The stork in the heavens knows its seasons, and the turtle dove , the swift and the crane keep the time of their arrival." In the Pacific, traditional land-finding techniques used by Micronesians and Polynesians suggest that bird migration was observed and interpreted for more than 3,000 years. In Samoan tradition, for example, Tagaloa sent his daughter Sina to Earth in the form of a bird, Tuli, to find dry land,
3200-531: The 'tubenose' order Procellariiformes , are great wanderers, and the albatrosses 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 among the longest-distance migrants; sooty shearwaters Puffinus griseus nesting on the Falkland Islands migrate 14,000 km (7,600 nmi) between
3280-853: The Black Sea surface and across high mountains. Birds of prey such as honey buzzards which migrate using thermals lose only 10 to 20% of their weight during migration, which may explain why they forage less during migration than do smaller birds of prey with more active flight such as falcons, hawks and harriers. From observing the migration of eleven soaring bird species over the Strait of Gibraltar, species which did not advance their autumn migration dates were those with declining breeding populations in Europe. 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
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3360-592: The Earth, flying over the southern oceans, while others such as Manx shearwaters migrate 14,000 km (8,700 mi) between their northern breeding grounds and the southern ocean. Shorter migrations are common, while longer ones are not. The shorter migrations include altitudinal migrations on mountains, including the Andes and Himalayas . The timing of migration seems to be controlled primarily by changes in day length. Migrating birds navigate using celestial cues from
3440-640: The Southern Hemisphere) to overwinter; In contrast, among (pelagic) seabirds, species of the Southern Hemisphere are more likely to migrate. This is because there is a large area of ocean in the Southern Hemisphere, and more islands suitable for seabirds to nest. 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
3520-517: The Sun and stars, the Earth's magnetic field, and mental maps. Writings of ancient Greeks recognized the seasonal comings and goings of birds. Aristotle wrote that birds transmuted into other birds or species like fish and animals, which explained their disappearance and reappearance. Aristotle thought many birds disappeared during cold weather because they were torpid , undetected in unseen environments like tree hollows or burrowing down in mud found at
3600-428: The appearance of Maniraptoromorpha, the next 40 million years marked a continuous reduction of body size and the accumulation of neotenic (juvenile-like) characteristics. Hypercarnivory became increasingly less common while braincases enlarged and forelimbs became longer. The integument evolved into complex, pennaceous feathers . The oldest known paravian (and probably the earliest avialan) fossils come from
3680-405: 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. The higher concentrations of migrating birds at stopover sites make them prone to parasites and pathogens, which require a heightened immune response. Within a species not all populations may be migratory; this
3760-778: The autumn than males do and the European tits of genera Parus and Cyanistes only migrate their first year. Most migrations begin with the birds starting off in a broad front. Often, this front narrows into one or more preferred routes termed flyways . 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 genetically programmed or learned to varying degrees. The routes taken on forward and return migration are often different. A common pattern in North America
3840-509: The birds that descended from them. Despite being currently one of the most widely used, the crown-group definition of Aves has been criticised by some researchers. Lee and Spencer (1997) argued that, contrary to what Gauthier defended, this definition would not increase the stability of the clade and the exact content of Aves will always be uncertain because any defined clade (either crown or not) will have few synapomorphies distinguishing it from its closest relatives. Their alternative definition
3920-628: The bottom of ponds, then reemerging months later. Still, Aristotle recorded that cranes traveled from the steppes of Scythia to marshes at the headwaters of the Nile , an observation repeated by Pliny the Elder in his Historia Naturalis . Two books of the Bible may address avian migration. The Book of Job notes migrations with the inquiry: "Is it by your insight that the hawk hovers, spreads its wings southward?" The Book of Jeremiah comments: "Even
4000-678: The breeding colony and the North Atlantic Ocean off Norway . Some Manx shearwaters Puffinus puffinus 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 kilometres (4.5 million nautical miles) during its over-50-year lifespan. Some large broad-winged birds rely on thermal columns of rising hot air to enable them to soar. These include many birds of prey such as vultures , eagles , and buzzards , but also storks . These birds migrate in
4080-488: The chaffinch are much less migratory in Britain than those of continental Europe, mostly not moving more than 5 km in their lives. Short-distance passerine migrants have two evolutionary origins. Those that have long-distance migrants in the same family, such as the common chiffchaff Phylloscopus collybita , are species of southern hemisphere origins that have progressively shortened their return migration to stay in
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#17327913171144160-455: The composition of a migrating flock, and can sometimes encode the sex of a migrating individual, and to avoid collision in the air. Nocturnal migration can be monitored using weather radar data, allowing ornithologists to estimate the number of birds migrating on a given night, and the direction of the migration. Future research includes the automatic detection and identification of nocturnally calling migrant birds. Nocturnal migrants land in
4240-498: The country in an irregular pattern, unrelated to season but related to rainfall. Several years may pass between visits to an area by a particular species. 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 waxwings Bombycilla garrulus well show this unpredictable variation in annual numbers, with five major arrivals in Britain during
4320-1040: The daintiest dish in England". The genus Limosa was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with the black-tailed godwit ( Limosa limosa ) as the type species . The genus name Limosa is from Latin and means "muddy", from limus , "mud". The English name "godwit" was first recorded in about 1416–17 and is believed to imitate the bird's call. The genus contains four living species: [REDACTED] Breeding Plumage [REDACTED] Non-Breeding Plumage [REDACTED] Breeding Plumage [REDACTED] Non-Breeding Plumage [REDACTED] Breeding Plumage [REDACTED] Non-Breeding Plumage [REDACTED] Breeding Plumage [REDACTED] Non-Breeding Plumage In addition, there are two or three species of fossil prehistoric godwits. Limosa vanrossemi
4400-499: 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. Mediterranean and other seas present a major obstacle to soaring birds, which must cross at the narrowest points. Massive numbers of large raptors and storks pass through areas such as the Strait of Messina , Gibraltar , Falsterbo , and
4480-665: The earliest members of Aves, is removed from this group, becoming a non-avian dinosaur instead. These proposals have been adopted by many researchers in the field of palaeontology and bird evolution , though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is often used synonymously with the vernacular term "bird" by these researchers. † Coelurus † Ornitholestes † Ornithomimosauria † Alvarezsauridae † Oviraptorosauria Paraves Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used
4560-412: 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. In addition, the longer days of the northern summer provide extended time for breeding birds to feed their young. This helps diurnal birds to produce larger clutches than related non-migratory species that remain in
4640-451: The first avialans were omnivores . The Late Jurassic Archaeopteryx is well known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. Archaeopteryx was the first fossil to display both clearly traditional reptilian characteristics—teeth, clawed fingers, and a long, lizard-like tail—as well as wings with flight feathers similar to those of modern birds. It
4720-418: The local temperature to time their spring migration departure. Notably, departure responses to temperature varied between individuals but were individually repeatable (when tracked over multiple years). This suggests that individual use of temperature is a cue that allows for population-level adaptation to climate change . In other words, in a warming world, many migratory birds are predicted to depart earlier in
4800-517: The loss. The typical image of migration is of northern land birds, such as swallows (Hirundinidae) and birds of prey, making long flights to the tropics. However, many Holarctic wildfowl and finch (Fringillidae) species winters in the North Temperate Zone , in regions with milder winters than their summer breeding grounds. For example, the pink-footed goose migrates from Iceland to Britain and neighbouring countries, whilst
4880-427: The morning and may feed for a few days before resuming their migration. These birds are referred to as passage migrants in the regions where they occur for a short period between the origin and destination. Nocturnal migrants minimize depredation, avoid overheating, and can feed during the day. One cost of nocturnal migration is the loss of sleep. Migrants may be able to alter their quality of sleep to compensate for
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#17327913171144960-502: The most direct line between breeding and wintering grounds. Rather, it could follow a hooked or arched line, with detours around geographical barriers or towards suitable stopover habitat. For most land birds, such barriers could consist of large water bodies or high mountain ranges, a lack of stopover or feeding sites, or a lack of thermal columns (important for broad-winged birds). Conversely, in water-birds , large areas of land without wetlands offering suitable feeding sites may present
5040-458: The nineteenth century, but 18 between the years 1937 and 2000. Red crossbills Loxia curvirostra too are irruptive, with widespread invasions across England noted in 1251, 1593, 1757, and 1791. Bird migration is primarily, but not entirely, a Northern Hemisphere phenomenon. This is because continental landmasses of the northern hemisphere are almost entirely temperate and subject to winter food shortages driving bird populations south (including
5120-456: The northern hemisphere. Species that have no long-distance migratory relatives, such as the waxwings Bombycilla , are effectively moving in response to winter weather and the loss of their usual winter food, rather than enhanced breeding opportunities. 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, but altitudinal migration occurs in some tropical birds. There
5200-523: The only known groups without wings are the extinct moa and elephant birds . Wings, which are modified forelimbs , gave birds the ability to fly, although further evolution has led to the loss of flight in some birds , including ratites , penguins , and diverse endemic island species. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds , have further evolved for swimming. The study of birds
5280-402: The outermost half) can be seen in the evolution of maniraptoromorphs, and this process culminated in the appearance of the pygostyle , an ossification of fused tail vertebrae. In the late Cretaceous, about 100 million years ago, the ancestors of all modern birds evolved a more open pelvis, allowing them to lay larger eggs compared to body size. Around 95 million years ago, they evolved
5360-536: The previously clear distinction between non-birds and birds has become blurred. By the 2000s, discoveries in the Liaoning Province of northeast China, which demonstrated many small theropod feathered dinosaurs , contributed to this ambiguity. The consensus view in contemporary palaeontology is that the flying theropods, or avialans , are the closest relatives of the deinonychosaurs , which include dromaeosaurids and troodontids . Together, these form
5440-965: The reverse pattern is seen in land birds. However most bird migration is in the range of 150 to 600 m (490–2,000 ft). Bird strike Aviation records from the United States show most collisions occur below 600 m (2,000 ft) and almost none above 1,800 m (5,900 ft). Bird migration is not limited to birds that can fly. Most species of penguin (Spheniscidae) migrate by swimming. These routes can cover over 1,000 km (550 nmi). Dusky grouse Dendragapus obscurus perform altitudinal migration mostly by walking. Emus Dromaius novaehollandiae in Australia have been observed to undertake long-distance movements on foot during droughts. During nocturnal migration ("nocmig" ), many birds give nocturnal flight calls, which are short, contact-type calls. These likely serve to maintain
5520-446: 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, changing their preferential direction at roughly the same time their wild conspecifics change course. Satellite tracking of 48 individual Asian houbaras ( Chlamydotis macqueenii ) across multiple migrations showed that this species uses
5600-452: The same biological name "Aves", which is a problem. The authors proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below. They assigned other names to the other groups. Lizards & snakes Turtles Crocodiles Birds Under the fourth definition Archaeopteryx , traditionally considered one of
5680-428: The same hemisphere, but others such as semipalmated sandpiper C. pusilla travel longer distances to the tropics in the Southern Hemisphere. 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
5760-551: The second toe which may have been held clear of the ground in life, and long feathers or "hind wings" covering the hind limbs and feet, which may have been used in aerial maneuvering. Avialans diversified into a wide variety of forms during the Cretaceous period. Many groups retained primitive characteristics , such as clawed wings and teeth, though the latter were lost independently in a number of avialan groups, including modern birds (Aves). Increasingly stiff tails (especially
5840-475: The social system of the species. In long-lived, social species such as white storks (Ciconia ciconia), flocks are often led by the oldest members and young storks learn the route on their first journey. In short-lived species that migrate alone, such as the Eurasian blackcap Sylvia atricapilla or the yellow-billed cuckoo Coccyzus americanus , first-year migrants follow a genetically determined route that
5920-718: The start of the next, travelling not just the length of the Atlantic Ocean and the width of the Indian Ocean, but also half way across the South Pacific to the boundary between the Ross and Amundsen Seas before returning back west along the Antarctic coast and back up the Atlantic. Many tubenosed birds breed in the southern hemisphere and migrate north in the southern winter. The most pelagic species, mainly in
6000-416: 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 migration. Predation can be heightened during migration: Eleonora's falcon Falco eleonorae , which breeds on Mediterranean islands, has a very late breeding season, coordinated with
6080-459: The winters. He concludes: These experiments have since been amply confirmed by ... M. Natterer , of Vienna ... and the result clearly proves, what is in fact now admitted on all hands, that Swallows do not in any material instance differ from other birds in their nature and propensities [for life in the air]; but that they leave us when this country can no longer furnish them with a supply of their proper and natural food ... In 1822,
6160-443: The word tuli referring specifically to land-finding waders, often to the Pacific golden plover. Aristotle, however, suggested that swallows and other birds hibernated. This belief persisted as late as 1878 when Elliott Coues listed the titles of no fewer than 182 papers dealing with the hibernation of swallows. Even the "highly observant" Gilbert White , in his posthumously published 1789 The Natural History of Selborne , quoted
6240-409: The world's 10,000 bird species are long-distance migrants. 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
6320-400: The year for their summer or winter destination. In polygynous species with considerable sexual dimorphism , males tend to return earlier to the breeding sites than their females. This is termed protandry. Birds Birds are a group of warm-blooded vertebrates constituting the class Aves ( Latin: [ˈaveːs] ), characterised by feathers , toothless beaked jaws,
6400-466: Was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae . Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use. Birds are categorised as the biological class Aves in Linnaean taxonomy . Phylogenetic taxonomy places Aves in the clade Theropoda as an infraclass or a subclass, more recently a subclass. Aves and
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