question: For the birds that don't migrate, how do they handle the frigid temperatures of Winter without dying?
comment: For birds in Britian, you will see them in branches of tree or electricity lines. They will be incredibly fat, to store energy when food is scarce and to keep them warm, having spent all autumn eating all they can find to survive the winter. They also puff up all their feathers, trapping a still layer of air close to them that warms up to stop their body heat being drawn away by cold wind, and find sheltered spots to hide in. If you want to help, winter is the best time for putting out birdseed or lard balls to help them stay fed when their usual diet of seeds and flies dies away for winter.
passages: Hazards during migration include storms, hunting, collisions with manmade objects such as wind turbines, and starvation. The risk of starvation is increased when stopover sites are lost through climate change or loss of habitat to development or agriculture. Mortality on both breeding and wintering grounds may be increased for similar reasons.
  
  Section::::Context.
  
  Migrants tend to travel away from polar and temperate zones in the winter because of low temperatures and shortage of food in their breeding areas. During spring migration, birds return to their breeding sites to exploit the temporary superabundance of food, allowing them to raise more young.
   Section::::Stress physiology.
  
  Section::::Stress physiology.:Weather.
  
  American kestrels are often useful in scientific studies on animal physiology, and are typically captured using the bal-chatri method or raised in nest boxes for experiments. Kestrel metabolic rate has been found to increase in response to rainfall, and at ambient temperatures below about 25⁰ C. Kestrel metabolic responses to weather and temperature do not vary, however, with sex. Kestrels will increase their oxygen consumption, and therefore their metabolic rate in cold and wet conditions to counteract heat loss.
  
  Section::::Stress physiology.:Environmental disturbance.
   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 geese "Branta canadensis", microlight aircraft were used in the US to teach safe migration routes to reintroduced whooping cranes "Grus americana".
  
  Section::::Adaptations.
   Bird migration perils
  
  Migrating birds face many perils as they travel between breeding and wintering grounds each year.
  
  Migration is a dangerous part of a bird's life cycle, with many trade-offs; birds receive benefits from wintering and breeding in better quality habitats, at the price of higher predation risks and greater energy expenditure.
   Migration routes and wintering grounds are both genetically and traditionally determined depending on 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 is alterable with selective breeding.
   Some predators take advantage of the concentration of birds during migration. Greater noctule bats feed on nocturnal migrating passerines. Some birds of prey specialize on migrating waders.
  
  Section::::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.
   Only birds that live in the extreme north and south of their range migrate and do so based on temperature and available sunlight. Anhingas will migrate towards the equator during winter but this range is "determined by the amount of sunshine to warm the chilled birds". Although not in their usual range, anhingas have been found as far north as the states of Pennsylvania and Wisconsin in the United States.
  
  Kettles of anhingas often migrate with other birds and have been described as resembling black paper gliders.
  
  Section::::Description.
   Reverse migration is more likely to occur with bird species that have low fat storage compared to higher fat storage.
   Section::::Physiology and control.: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" in which birds returning to their breeding areas overshoot and end up further north than intended. Certain areas, because of their location, have become famous as watchpoints for such birds. Examples are the Point Pelee National Park in Canada, and Spurn in England.
  
  Reverse migration, where the genetic programming of young birds fails to work properly, can lead to rarities turning up as vagrants thousands of kilometres out of range.
   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 the same hemisphere, but others such as semipalmated sandpiper "C. pusilla" travel longer distances to the tropics in the Southern Hemisphere.
   In-flight mortality: poor weather conditions can significantly decrease bird populations, especially during migration. Most of weather-related in-flight mortalities are due to heavy storms, mist or rain. Passerines and other small sized birds are particularly affected by adverse in-flight weather conditions, but larger birds such as eagles and swans could also be killed.
  
  Mortality on breeding grounds: small, insect eating birds contribute to the majority of post-arrival deaths, but many other birds including waders and waterfowls are also distressed by weather changes on breeding grounds. Since young birds are inexperienced, they are more vulnerable than adults to extreme weather conditions.
   In relation to temperature and precipitation, common ravens are exposed to changing seasons with climate extremes. Within the common raven species, the degree of climatic seasonality is related to the magnitude of fluctuations in basal metabolic rate and total evaporative water loss. For instance, populations living in Alberta are subjected to both extremely cold temperatures in the winter and very hot and dry weather during the summer months. Furthermore, the common raven is not known to migrate long distances to avoid the winter season, so it is required to regulate and cope with the environmental conditions.
   BULLET::::- Eight pairs of spoonbills fledged 14 young at Holkham NNR, Norfolk, the second year spoonbills fledged here.
  
  BULLET::::- Norway donated sixteen white-tailed eagles as part of the East Scotland sea eagle reintroduction project.
  
  BULLET::::- The first record of a displaying great snipe came from 11–16 May at Cley where one was seen lekking.
  
  BULLET::::- Red-backed shrike bred on Dartmoor for the second consecutive year. This species bred in the UK until the 1990s and last bred on Dartmoor in 1970.
  
  BULLET::::- Seabirds in Scotland continue to struggle with poor breeding performances in many colonies.
  
  Section::::Europe.:Britain.:Migrant and wintering birds.
   Section::::See also.
  
  BULLET::::- Ambelopoulia
  
  BULLET::::- "Winged Migration", 2001 documentary film
  
  BULLET::::- Isoscapes
  
  BULLET::::- Smithsonian Migratory Bird Center
  
  Section::::Further reading.
  
  BULLET::::- (first published 1982 as "Fågelflyttning", Bokförlaget Signum)
  
  Section::::External links.
  
  BULLET::::- Dedicated issue of "Philosophical Transactions B" on Adaptation to the Annual Cycle.
  
  BULLET::::- Route of East Asian Migratory Flyaway Olango Wildlife Sanctuary as a refuelling station of migratory birds
  
  BULLET::::- Migration Ecology Group, Lund University, Sweden
  
  BULLET::::- Migrate.ou.edu – Migration Interest Group: Research Applied Toward Education, USA
  
  BULLET::::- Canadian Migration Monitoring Network (Co-ordinates bird migration monitoring stations across Canada)
   Section::::Behaviour and ecology.:Migration.
  
  European breeders winter in Africa. American and Canadian breeders winter in South America, although some stay in the southernmost U.S. states such as Florida and California. Some ospreys from Florida migrate to South America. Australasian ospreys tend not to migrate.
   Circadian Migration is where birds utilize circadian rhythm (CR) to regulate migration in both the fall and the spring. In circadian migration clocks of both circadian (daily) and circannual (annual) patterns are utilized to determine the birds’ orientation in both time and space as they migrate from one destination to the next. This type of migration is advantageous in birds that during the winter remain close to the equator, and also allows the monitoring of the auditory and spatial memory of the birds’ brain to remember an optimal site of migration. These birds also have timing mechanisms that provide avians with the distance required to travel in order to reach their destination. To regulate the migration patterns of these birds, the mammalian circadian clock is utilized. This clock allows the avians to determine when the appropriate time is to migrate, which location will best help the birds regulate their metabolism, and whether land or water travel will be most advantageous for these migrating species.
   The birds are released in late January or early February to breed outside the cages on ledges and, mainly, in the nest boxes in the breeding station compound. The ibises are free flying and forage around the Birecik area in forest nurseries, agricultural fields, and along the Euphrates, but supplementary food is also provided. Following the end of the breeding season, the birds are taken into cages in late July or early August to prevent migration. A trial migration using tagged birds confirmed the risks presented to travelling birds by pesticides. Later on the Syrian Civil War added one more reason to keep preventing migration.
   Section::::Reverse migration is genetic or learned behaviour?
  
  Some large birds such as swans learn migration routes from their parents. However, in most small species, such as passerines, the route is genetically programmed, and young birds can innately navigate to their wintering area. Sometimes this programming goes wrong, and the young bird, in its first autumn, migrates on a route 180° from the correct route. This is shown in the diagram, where the typical migration route is shown in red but a reverse migration has occurred as seen in orange in the image.
   In autumn, some young birds, instead of heading to their usual wintering grounds, take "incorrect" courses and migrate through areas which are not on their normal migration path. For example, Siberian passerines which normally winter in Southeast Asia are commonly found in Northwest Europe, e.g. Arctic warblers in Britain. This is reverse migration, where the birds migrate in the opposite direction to that expected (say, flying north-west instead of south-east). The causes of this are unknown, but genetic mutation or other anomalies relating to the bird's magnetic sensibilities is suspected.
   So with some species such as swans that the migration route is learned and reverse migration could occur from learning improper route from parents or other birds.
   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 may also be a barrier to a bird that feeds in coastal waters. Detours avoiding such barriers are observed: for example, brent geese "Branta bernicla" 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.
  
  Section::::Long-distance migration.:In waders.
   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 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.
   Section::::Long-distance migration.:Diurnal migration in raptors.
   Mortality on wintering grounds: Unreasonably cold temperatures on the wintering grounds kills thousands of birds, resulting in 30-90% population declines of migratory birds. For example, between 27000 and 62000 ducks, mostly tufted duck and common pochard, starved to death during a very cold winter in March 1986.
  
  Section::::Immediate perils.:Hunting.
   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 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.
  