question: How do birds last so long flapping their wings non-stop?
comment: Also, they generally don’t go non-stop. Flap, flap, glide for a while, etc. They also follow air currents. use uprises, and fly in formations to minimize air resistance.
passages: Section::::Episodes.:10. "The Limits of Endurance".
   The large amounts of energy required for flight have led to the evolution of a unidirectional pulmonary system to provide the large quantities of oxygen required for their high respiratory rates. This high metabolic rate produces large quantities of radicals in the cells that can damage DNA and lead to tumours. Birds, however, do not suffer from an otherwise expected shortened lifespan as their cells have evolved a more efficient antioxidant system than those found in other animals. 
  
  Section::::Evolution of bird flight.
   Due to the high metabolic rate required for flight, birds have a high oxygen demand. Their highly effective respiratory system helps them meet that demand.
   Section::::Episodes.:2. "The Mastery of Flight".
   Similarly, even when blind, house sparrows continue to be photoperiodic, i.e. show reproductive development when the days are long, but not when the days are short. This response is stronger when the feathers on top of the head are plucked, and is eliminated when India ink is injected under the skin at the top of the head, showing that the photoreceptors involved in the photoperiodic response to day length are located inside the brain.
   However, the ratio of resting metabolic rate to total daily energy expenditure can vary between 1.6 and 8.0 between species of mammals. Animals also vary in the degree of coupling between oxidative phosphorylation and ATP production, the amount of saturated fat in mitochondrial membranes, the amount of DNA repair, and many other factors that affect maximum life span. Furthermore, a number of species with high metabolic rate, like bats and birds, are long-lived. In a 2007 analysis it was shown that, when modern statistical methods for correcting for the effects of body size and phylogeny are employed, metabolic rate does not correlate with longevity in mammals or birds.
   Survival often depends on an animal's ability to time intervals. For example, rufous hummingbirds feed on the nectar of flowers, and they often return to the same flower, but only after the flower has had enough time to replenish its supply of nectar. In one experiment hummingbirds fed on artificial flowers that quickly emptied of nectar but were refilled at some fixed time (e.g. twenty minutes) later. The birds learned to come back to the flowers at about the right time, learning the refill rates of up to eight separate flowers and remembering how long ago they had visited each one.
   Section::::Research data.
  
  BULLET::::- A comparison of the heart mitochondria in rats (7-year maximum life span) and pigeons (35-year maximum life span) showed that pigeon mitochondria leak fewer free-radicals than rat mitochondria, despite the fact that both animals have similar metabolic rate and cardiac output
  
  BULLET::::- For mammals there is a direct relationship between mitochondrial membrane fatty acid saturation and maximum life span
  
  BULLET::::- Studies of the liver lipids of mammals and a bird (pigeon) show an inverse relationship between maximum life span and number of double bonds
   Except when nesting, swifts spend their lives in the air, living on the insects caught in flight; they drink, feed, and often mate and sleep on the wing. Some individuals go 10 months without landing. No other bird spends as much of its life in flight. Their maximum horizontal flying speed is 111.6 km/h. Over a lifetime they can cover millions of kilometers.
   While there may be some validity to the idea that for various types of specific damage detailed below that are by-products of metabolism, all other things being equal, a fast metabolism may reduce lifespan, in general this theory does not adequately explain the differences in lifespan either within, or between, species. Calorically restricted animals process as much, or more, calories per gram of body mass, as their "ad libitum" fed counterparts, yet exhibit substantially longer lifespans. Similarly, metabolic rate is a poor predictor of lifespan for birds, bats and other species that, it is presumed, have reduced mortality from predation, and therefore have evolved long lifespans even in the presence of very high metabolic rates. In a 2007 analysis it was shown that, when modern statistical methods for correcting for the effects of body size and phylogeny are employed, metabolic rate does not correlate with longevity in mammals or birds. (For a critique of the "Rate of Living Hypothesis" see "Living fast, dying when?")
   Hummingbirds have one of the highest metabolic rates of any animal, with heart rates up to 1260 beats per minute, breathing rate of about 250 breaths per minute even at rest, and oxygen consumption of about 4 ml oxygen/g/hour at rest. During flight, hummingbird oxygen consumption per gram of muscle tissue is approximately 10 times higher than that seen for elite human athletes.
  
  They feed frequently while active during the day. When temperatures drop, particularly on cold nights, they may conserve energy by entering hypothermic .
  
  Section::::Flight.
   The maximum age recorded is 25 years and 8 months for a ringed bird in Germany. The longevity record for Britain and Ireland is 23 years and 10 months for a bird found dead in Wales in 2012.
  
  Section::::Behaviour.:Food and feeding.
   Hummingbirds have the greatest mass-specific metabolic rate of any homeothermic animal. To conserve energy when food is scarce, and nightly when not foraging, they can go into torpor, a state similar to hibernation, slowing metabolic rate to 1/15th of its normal rate.
  
  Section::::Evolution.
   With the exception of insects, hummingbirds while in flight have the highest metabolism of all animals – a necessity to support the rapid beating of their wings during hovering and fast forward flight. Their heart rate can reach as high as 1,260 beats per minute, a rate once measured in a blue-throated hummingbird, with a breathing rate of 250 breaths per minute, even at rest. During flight, oxygen consumption per gram of muscle tissue in a hummingbird is about 10 times higher than that measured in elite human athletes.
   Hummingbirds do not spend all day flying, as the energy cost would be prohibitive; the majority of their activity consists simply of sitting or perching. Hummingbirds eat many small meals and consume around half their weight in nectar (twice their weight in nectar, if the nectar is 25% sugar) each day. Hummingbirds digest their food rapidly due to their small size and high metabolism; a mean retention time less than an hour has been reported. Hummingbirds spend an average of 10–15% of their time feeding and 75–80% sitting and digesting.
   BULLET::::- The tuatara, a lizard-like reptile native to New Zealand, can live well over 100 years. Henry, a tuatara at the Southland Museum in New Zealand, mated for the first time at the estimated age of 111 years in 2009 with an 80-year-old female and fathered 11 baby tuatara.
   A number of animals have separately evolved gliding many times, without any single ancestor. Birds in particular use gliding flight to minimise their use of energy. Large birds are notably adept at gliding, including:
  
  BULLET::::- Albatross
  
  BULLET::::- Condor
  
  BULLET::::- Vulture
  
  BULLET::::- Eagle
  
  BULLET::::- Stork
  
  BULLET::::- Frigatebird
  
  Like recreational aircraft, birds can alternate periods of gliding with periods of soaring in rising air, and so spend a considerable time airborne with a minimal expenditure of energy. The great frigatebird in particular is capable of continuous flights up to several weeks.
  
  Section::::Gliding animals.:Mammals.
   BULLET::::- Cookie, (hatched June 30, 1933) an Australian-born Major Mitchell's cockatoo resident at Brookfield Zoo, Illinois, was the oldest member of his species in captivity, and died in August 2016 at a verified age of 83.
  
  BULLET::::- Muja, an American alligator from Belgrade Zoo, is considered to be the oldest alligator in the world. Muja is more than 80 years old.
  
  BULLET::::- Thaao, an Andean condor, died at the age of 80.
   The metabolism of hummingbirds can slow at night or at any time when food is not readily available: the birds enter a hibernation-like, deep-sleep state (known as torpor) to prevent energy reserves from falling to a critical level. During night-time torpor, body temperature falls from 40 to 18 °C, with heart and breathing rates both slowed dramatically (heart rate to roughly 50 to 180 beats per minute from its daytime rate of higher than 1000).
   BULLET::::- There is a direct correlation between DNA repair and maximum life span for mammalian species
  
  BULLET::::- Drosophila (fruit-flies) bred for 15 generations by only using eggs that were laid toward the end of reproductive life achieved maximum life spans 30% greater than that of controls
  
  BULLET::::- Overexpression of the enzyme which synthesizes glutathione in long-lived transgenic "Drosophila" (fruit-flies) extended maximum lifespan by nearly 50%
   David Stratton wrote of it:
   Section::::Episodes.:5. "Fishing for a Living".
   Birds have a four-chambered heart, in common with mammals, and some reptiles (mainly the crocodilia). This adaptation allows for an efficient nutrient and oxygen transport throughout the body, providing birds with energy to fly and maintain high levels of activity. A ruby-throated hummingbird's heart beats up to 1200 times per minute (about 20 beats per second).
  
  Section::::Digestive system.
  
  Section::::Digestive system.:Crop.
   BULLET::::- A comparison of 7 non-primate mammals (mouse, hamster, rat, guinea-pig, rabbit, pig and cow) showed that the rate of mitochondrial superoxide and hydrogen peroxide production in heart and kidney were inversely correlated with maximum life span
  
  BULLET::::- A study of 8 non-primate mammals showed an inverse correlation between maximum life span and oxidative damage to mtDNA (mitochondrial DNA) in heart & brain
  
  BULLET::::- A study of several species of mammals and a bird (pigeon) indicated a linear relationship between oxidative damage to protein and maximum life span
   A number of bird species appear to be in the process of losing their powers of flight to various extents. These include the Zapata rail of Cuba, the Okinawa rail of Japan, and the Laysan duck of Hawaii. All of these birds show adaptations common to flightlessness, and evolved recently from fully flighted ancestors, but have not yet completely given up the ability to fly. They are, however, weak fliers and are incapable of traveling long distances by air.
  
  Section::::Morphological changes and energy conservation.:Continued presence of wings in flightless birds.
  
presuppositions: Birds flap their wings continuously. Birds flap their wings nonstop.
corrections: Bird pause and glide in between flaps. Birds don't generally flap their wings nonstop.
raw_presuppositions: Birds flap their wings continuously. Birds flap their wings nonstop.
raw_corrections: Bird pause and glide in between flaps. Birds don't generally flap their wings nonstop.