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Cited by 141High Altitude and HypoxiaPhysiological and biochemical adaptationsBiomimetic flight and propulsion mechanisms

The physiology and biomechanics of avian flight at high altitude

Altshuler, D. L.·2006·Integrative and Comparative Biology
DOI 10.1093/icb/icj008
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Abstract

Many birds fly at high altitude, either during long-distance flights or by virtue of residence in high-elevation habitats. Among the many environmental features that vary systematically with altitude, five have significant consequences for avian flight performance: ambient wind speeds, air temperature, humidity, oxygen availability, and air density. During migratory flights, birds select flight altitudes that minimize energy expenditure via selection of advantageous tail- and cross-winds. Oxygen partial pressure decreases substantially to as little as 26% of sea-level values for the highest altitudes at which birds migrate, whereas many taxa reside above 3000 meters in hypoxic air. Birds exhibit numerous adaptations in pulmonary, cardiovascular, and muscular systems to alleviate such hypoxia. The systematic decrease in air density with altitude can lead to a benefit for forward flight through reduced drag but imposes an increased aerodynamic demand for hovering by degrading lift production and simultaneously elevating the induced power requirements of flight. This effect has been well-studied in the hovering flight of hummingbirds, which occur throughout high-elevation habitats in the western hemisphere. Phylogenetically controlled studies have shown that hummingbirds compensate morphologically for such hypodense air through relative increases in wing size, and kinematically via increased stroke amplitude during the wingbeat. Such compensatory mechanisms result in fairly constant power requirements for hovering at different elevations, but decrease the margin of excess power available for other flight behaviors.

Integrity signals

Registry

Crossref · 10.1093/icb/icj008

Cites

89 of 89 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

1 of 94 cited sources checked · 1 supported · 0 flagged

  • Premisecitation

    Research on avian flight has typically been conducted at or near sea-level conditions for anthropogenic reasons deriving from contemporary altitudinal distribution of modern humans.

    “Research on avian flight has, for anthropogenic reasons deriving from contemporary altitudinal distribution of modern humans (Cohen and Small, 1998), typically been conducted at or near sea-level conditions.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Cohen and Small, 1998 source
  • Findingown data

    Stroke amplitude during hovering exhibited a systematic increase among species at higher elevations.

    “Stroke amplitude during hovering exhibited a systematic increase among species at higher elevations”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Altshuler and Dudley, 2003 source
    • cites Altshuler et al., 2004b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Findingreasoning

    The power reserve systematically declines at higher elevation.

    “The power reserve thus systematically declines at higher elevation (Fig. 2)”
    • Also stated in: § Conclusions · plain
      “Hummingbird power margin decreases with elevation.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Altshuler et al., 2004b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Findingown data

    Hummingbirds failed to perform sustained hovering at specific oxygen- or density-equivalent elevations during density- and oxygen-reduction trials.

    “Oxygen-or density-equivalent elevations at which hummingbirds failed to perform sustained hovering during density-and oxygen-reduction trials*”
    Quote in the paperSubstantial claim
  • Findingcitation

    Load-lifting elicits maximum stroke amplitudes in all taxa.

    “load-lifting elicits maximum stroke amplitudes in all taxa”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Altshuler et al., 2004b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims. 29
  • Classified as probably not a substantial claim. 21

  • May combine two claims.

    Findingcitation

    Among species, the mass-specific aerodynamic power requirements for hovering flight are approximately constant with respect to altitude, because of systematic interspecific increases in relative wing size and in stroke amplitude at higher elevations.

    “Among species, the mass-specific aerodynamic power requirements for hovering flight are approximately constant with respect to altitude, because of systematic interspecific increases in relative wing size and in stroke amplitude at higher elevations.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Altshuler et al., 2004b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingcitation

    Wingbeat frequency declined as predicted on allometric grounds with body mass but was uncorrelated with elevation.

    “Wingbeat frequency, by contrast, declined as predicted on allometric grounds with body mass but was uncorrelated with elevation.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Altshuler and Dudley, 2003 source
    • cites Altshuler et al., 2004b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingreasoning

    Higher-elevation hummingbirds already hover with increased stroke amplitudes, and correspondingly possess less reserve capacity in wing motions and related power production supplemental to that required for normal hovering.

    “higher-elevation hummingbirds already hover with increased stroke amplitudes, they correspondingly possess less reserve capacity in wing motions and related power production supplemental to that required for normal hovering”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Altshuler et al., 2004b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Premisenone given

    Birds exhibit numerous adaptations in pulmonary, cardiovascular, and muscular systems to alleviate hypoxia.

    “Birds exhibit numerous adaptations in pulmonary, cardiovascular, and muscular systems to alleviate such hypoxia.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Migrating birds may be alternatively impeded or aided by higher wind speeds if the wind direction is against or in the direction of desired forward progress.

    “Migrating birds, on the other hand, may be alternatively impeded or aided by higher wind speeds if the wind direction is against or in the direction of desired forward progress, respectively (Green et al., 2004).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Green et al., 2004 source

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    Many bird taxa are high-elevation specialists, and a large number of migrants fly at substantial altitude.

    “Nonetheless, many bird taxa are high-elevation specialists, and a large number of migrants fly at substantial altitude.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    During migratory flights, birds select flight altitudes that minimize energy expenditure via selection of advantageous tail- and crosswinds.

    “During migratory flights, birds select flight altitudes that minimize energy expenditure via selection of advantageous tail-and crosswinds.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The oxygen delivery systems of birds function well across a broad range of oxygen partial pressures and exhibit considerable adaptive plasticity when rapidly exposed to deep hypoxia.

    “In summary, the oxygen delivery systems of birds function well across a broad range of oxygen partial pressures and exhibits considerable adaptive plasticity when rapidly exposed to deep hypoxia (Shams and Scheid, 1993).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Shams and Scheid, 1993 source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    In contrast with many mammals, birds subjected experimentally to low barometric pressures do not exhibit some of the most maladaptive responses.

    “In contrast with many mammals, birds subjected experimentally to low barometric pressures do not exhibit some of the most maladaptive responses.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Blood leaving the lung interface can have the same oxygen partial pressure as inspired air, indicating that oxygen delivery in birds is not limited by the pulmonary system.

    “The net result of these adaptations is that blood leaving the lung interface can have the same oxygen partial pressure as inspired air, indicating that oxygen delivery in birds is not limited by the pulmonary system (Fedde, 1990).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Fedde, 1990 source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Many avian taxa reside above 3000 m in hypoxic air.

    “whereas many taxa reside above 3000 meters in hypoxic air.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In response to hypobaria, birds increase overall rates of oxygen consumption and respiratory rates, whereas these parameters decrease for mice.

    “Similarly in response to hypobaria, birds increase overall rates of oxygen consumption and respiratory rates, whereas these parameters decrease for mice (Tucker, 1968b).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Tucker, 1968b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisereasoning

    Aerodynamic forces typically vary in linear proportion to air density, so morphological and kinematic compensation is necessary to effect flight at different elevations.

    “Because aerodynamic forces typically vary in linear proportion to air density, morphological and kinematic compensation is necessary to effect flight at different elevations.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Aerodynamic forces vary in linear proportion to air density.

  • May combine two claims.

    Premisenone given

    Five environmental features vary systematically with altitude and have significant consequences for avian flight performance: ambient wind speeds, air temperature, humidity, oxygen availability, and air density.

    “Among the many environmental features that vary systematically with altitude, five have significant consequences for avian flight performance: ambient wind speeds, air temperature, humidity, oxygen availability, and air density.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    Sea-level density of air at 20 C is about 1.21 kg/m3, decreasing to 0.95 kg/m3 at 2000 m elevation and 0.74 kg/m3 at 4000 m, the latter being a 40% reduction relative to sea-level.

    “Sea-level density of air at 20 C is about 1.21 kg/m 3 , decreasing to 0.95 kg/m 3 at 2000 m elevation and 0.74 kg/m 3 at 4000 m, the latter being a 40% reduction relative to the sea-level value.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Morphological, behavioral, and physiological adaptations to altitude must correspondingly pertain.

    “Morphological, behavioral, and physiological adaptations to altitude must correspondingly pertain.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Aerodynamic models predict an increase in cruising flight speed with altitude at the approximate rate of 5% per 1000 m, primarily because of the reduction in wing and body drag, and because of the relatively small magnitude of induced power in forward flight relative to other components of energetic expenditure.

    “Specifically, aerodynamic models predict an increase in cruising flight speed with altitude at the approximate rate of 5% per 1000 m, primarily because of the reduction in wing and body drag, and because of the relatively small magnitude of induced power in forward flight relative to other components of energetic expenditure (Pennycuick, 1978;Hedenstro ¨m, 2003).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Pennycuick, 1978 source
    • cites Hedenström, 2003 source

  • May combine two claims.

    Premisecitation

    Hummingbirds inhabit high elevations throughout the New World, with some taxa residing up to 5000 m.

    “but these birds nevertheless inhabit high elevations throughout the New World (Schuchmann, 1999), with some taxa residing up to 5000 m (Carpenter, 1976;Rahbek and Graves, 2000).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Schuchmann, 1999

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Carpenter, 1976
    • cites Rahbek and Graves, 2000 source

  • May combine two claims.

    Premisecitation

    Endurance in the wind tunnel decreased substantially with decreasing pressure, although one bird provided with supplemental oxygen apparently flew better than the birds breathing rarefied air.

    “Endurance in the wind tunnel decreased substantially with decreasing pressure, although one bird provided with supplemental oxygen apparently flew better than the birds breathing rarefied air (Tucker, 1968b).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Tucker, 1968b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    In some taxa, departure probabilities are strongly correlated with the presence of favorable tailwinds, whereas other taxa only depart when winds are absent or weak regardless of wind direction.

    “In some cases, departure probabilities are strongly correlated with the presence of favorable tailwinds (e.g., A ˚kesson and Hedenstro ¨m, 2000;Klaassen et al., 2004), whereas other taxa only depart when winds are absent or weak regardless of wind direction (e.g., Schaub et al., 2004).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Åkesson and Hedenström, 2000 source
    • cites Klaassen et al., 2004 source
    • cites Schaub et al., 2004 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    No one else has used a hypobaric wind tunnel to study forward flight in birds.

    “To our knowledge, no one else has used a hypobaric wind tunnel to study forward flight in birds, although this would represent another compelling test of Pennycuick's (1978) hypothesis.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Theoretical analysis predicts that by accounting for wind conditions, birds could double their ground speed and accordingly save as much as half of the energy required for migratory flights.

    “Theoretical analysis also predicts that by accounting for wind conditions, birds could double their ground speed and accordingly save as much as half of the energy required for migratory flights (Liechti and Bruderer, 1998).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Liechti and Bruderer, 1998 source

  • May combine two claims.

    Premisecitation

    Under laboratory conditions, rates of oxygen consumption by hovering hummingbirds increase under reduced total pressure and under hypodense but normoxic conditions.

    “Under laboratory conditions, rates of oxygen consumption by hovering hummingbirds increases under reduced total pressure (Berger, 1974a,b) and under hypodense but normoxic conditions (Chai and Dudley, 1995).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Berger, 1974a,b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Chai and Dudley, 1995 source

  • May combine two claims.

    Premisecitation

    Providing supplemental oxygen does not increase aerodynamic performance in hypodense gas, but does allow for longer hovering durations when challenged aerodynamically.

    “Providing supplemental oxygen does not increase aerodynamic performance in hypodense gas (Chai et al., 1996), but does allow for longer hovering durations when challenged aerodynamically (Altshuler et al., 2001).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Chai et al., 1996

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Altshuler et al., 2001 source

  • Classified as probably not a substantial claim.

    Premisecitation

    In a computer-simulation model, respiratory dehydration would ultimately limit flight duration and distance, particularly in birds with sufficient fat stores to energetically fuel their flight.

    “In a computersimulation model, Carmi et al. (1992) concluded that respiratory dehydration would ultimately limit flight duration and distance, particularly in birds with sufficient fat stores to energetically fuel their flight.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Carmi et al., 1992

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    The effects of hypobaria on more diverse features of the avian flight envelope, including takeoff performance and maneuverability, are unstudied.

    “Also unstudied are the effects of hypobaria on more diverse features of the avian flight envelope, including takeoff performance and maneuverability.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Body water content can remain constant even as both birds and mammals undergo critical water stress, and thus may be a poor predictor of dehydration state.

    “However, Klaassen (2004) has pointed out that body water content can remain constant even as both birds and mammals undergo critical water stress, and thus may be a poor predictor of dehydration state.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Klaassen, 2004 source

  • May combine two claims.

    Interpretationreasoning

    A range of compensatory morphological, physiological, and biomechanical adaptations may have permitted larger hummingbirds to progressively colonize higher elevations in South America, but this outcome has not been entirely without cost.

    “A range of compensatory morphological, physiological, and biomechanical adaptations may have permitted larger hummingbirds to progressively colonize higher elevations in South America, but this outcome has not been entirely without cost.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Biotic factors also vary with elevation, although their influence on flight performance has received less attention than physical factors.

    “Biotic factors also vary with elevation, although their influence on flight performance has received less attention than physical factors.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Respiratory physiology has been the best studied type of such responses, and diverse adaptations are evident in the design of respiratory systems, oxygen-blood transport, and overall hypoxia resistance.

    “Respiratory physiology has been the best studied type of such responses, and diverse adaptations are evident in the design of respiratory systems, oxygen-blood transport, and overall hypoxia resistance.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Birds can respond on behavioral, ecological, and evolutionary timescales.

    “Birds in turn can respond on behavioral, ecological, and evolutionary timescales.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Altitudinal gradients in ambient winds are often used by avian migrants to enhance groundspeeds and overall energetic efficiency of migration.

    “Altitudinal gradients in ambient winds are often used by avian migrants to enhance groundspeeds and overall energetic efficiency of migration.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    During hovering, drag forces on the body are, by definition, nonexistent and induced power requirements to offset gravity are a dominant avenue of energy expenditure.

    “During hovering, drag forces on the body are, by definition, nonexistent and induced power requirements to offset gravity are a dominant avenue of energy expenditure.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Berger (1974a) experimentally imposed hypobaria on two species of montane hummingbirds, and elicited systematic increases in stroke amplitude and wing angle of attack.

    “Berger (1974a) experimentally imposed hypobaria on two species of montane hummingbirds, and elicited systematic increases in stroke amplitude and wing angle of attack”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Berger, 1974a

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Wingbeat kinematics of the Giant Andean Hummingbird are noticeably different at half-stroke transitions relative to those of other hummingbirds.

    “Wingbeat kinematics of the Giant Andean Hummingbird are noticeably different at half-stroke transitions relative to those of other hummingbirds”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites M.-J. Fernandez, pers. comm.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    Behavioral means of compensation to the adverse energetics of high-altitude flight are possible.

    “Behavioral means of compensation to the adverse energetics of high-altitude flight are also possible.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: High-altitude hummingbirds often perch while feeding, whereas their lowland counterparts almost never do so.

  • May combine two claims.

    Interpretationnone given

    These effects are likely to be of secondary importance for long-distance avian migrants, but must impinge substantially on the flight biology of high-altitude residents as well as of altitudinal migrants.

    “These effects are likely to be of secondary importance for long-distance avian migrants, but must impinge substantially on the flight biology of high-altitude residents as well as of altitudinal migrants.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    Hummingbirds (family Trochilidae) represent an ideal taxon with which to evaluate questions of physiological and biomechanical adaptation to high elevation.

    “Hummingbirds (family Trochilidae) represent an ideal taxon with which to evaluate such questions of physiological and biomechanical adaptation to high elevation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    Reductions in oxygen partial pressure, air density, and air temperature all potentially exert major influences on avian flight physiology.

    “Reductions in oxygen partial pressure, air density, and air temperature all potentially exert major influences on avian flight physiology.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Reduced air density at high elevation imposes aerodynamic and energetic costs on hovering, but a number of compensatory responses in flight-related morphology and biomechanics have now been demonstrated among different hummingbird species across elevational gradients.

    “Accordingly, reduced air density at high elevation imposes aerodynamic and energetic costs on hovering, but a number of compensatory responses in flight-related morphology and biomechanics have now been demonstrated among different hummingbird species across elevational gradients.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Such diminished reserves should also be evident in individual birds that migrate seasonally to higher elevations.

    “Such diminished reserves should also be evident in individual birds that migrate seasonally to higher elevations.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    A systematic increase in stroke amplitude at constant wingbeat frequency increases relative wing speed to overcome otherwise declining lift production, and simultaneously mitigates the enhanced induced power expenditure associated with hypodense air.

    “Overall, such a systematic increase in stroke amplitude at constant wingbeat frequency increase relative wing speed to overcome otherwise declining lift production, and simultaneously mitigate the enhanced induced power expenditure associated with hypodense air”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ellington, 1984b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    Relevant data are extremely limited, and overall the variation in wind velocity, oxygen partial pressure and in air density with altitude are of primary relevance to the mechanics and physiology of avian flight.

    “Relevant data are however extremely limited, and overall the variation in wind velocity, oxygen partial pressure and in air density with altitude are of primary relevance to the mechanics and physiology of avian flight.”
    Quote in the paperNot a substantial claim
43 of 43

  • The paper relies on this without support.

    Aerodynamic forces vary in linear proportion to air density.

    “Because aerodynamic forces typically vary in linear proportion to air density, morphological and kinematic compensation is necessary to effect flight at different elevations.”

  • The paper relies on this without support.

    The environmental lapse rate in air temperature remains linear within the troposphere.

    “The environmental lapse rate in air temperature through adiabatic cooling and increase in water content is about 0.65 C/100 m, and remains linearly so within the troposphere, so that an approximately 26 C difference characterizes air at 4000 m relative to that at sea level.”

  • The paper relies on this without support.

    Laboratory decoupling of air density and oxygen partial pressure can reveal the physiological and aerodynamic consequences of high-altitude flight.

    “Because it is possible to experimentally decouple air density and oxygen partial pressure in laboratory contexts (Dudley and Chai, 1996), we can examine the physiological and aerodynamic consequences of high-altitude flight both separately and in concert.”

  • The paper relies on this without support.

    Air density declines systematically with increased elevation.

    “The systematic decline in air density with increased elevation must adversely affect the aerodynamics of hovering flight.”

  • The paper relies on this without support.

    High-altitude hummingbirds often perch while feeding, whereas their lowland counterparts almost never do so.

    “Highaltitude hummingbirds, for example, often perch while feeding, whereas their lowland counterparts almost never do so.”

  • The paper relies on this without support.

    Some of the larger hummingbird species are most common at high altitudes.

    “Some of the larger species are, somewhat paradoxically, most common at high altitudes, exacerbating the demands of hovering flight.”

  • The paper relies on this without support.

    Ecosystem composition, predators, nutritional resources, and vegetational structure all change dramatically across elevational gradients.

    “Clearly, ecosystem composition, predators, nutritional resources, and vegetational structure all change dramatically across elevational gradients.”
7 of 7

Cites

Flagged first, then by citations

6 of the 95 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. [74]74. In J. del Hoyo, A. Elliott, and J. Sargatal (eds), Handbook to the Birds of the World, pp. 468-680. Lynx Edicions, Barcelona.

Cited by

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Related

Authors
Altshuler, D. L.
Affiliations
California Institute of Technology (US)
Corresponding author
Altshuler, D. L.
ORCID
Altshuler, D. L.
Venue
Integrative and Comparative Biology
Publisher
Oxford University Press (OUP)
Published
2006-01-06
Volume
46
Issue
1
Pages
62-71
ISSN
  • 1540-7063 (ISSN-L)
  • 1557-7023
DOI
10.1093/icb/icj008
OpenAlex
W2042695519
Cited by
141
References
95
Citations by year
2026: 6 · 2025: 8 · 2024: 7 · 2023: 9 · 2022: 13 · 2021: 31 · 2020: 8 · 2019: 6 · 2018: 5 · 2017: 9 · 2016: 3 · 2015: 8 · 2014: 4 · 2013: 2 · 2012: 3
FWCI
1.52
Type
journal article
Language
en
Open access
closed
Locations
  • Integrative and Comparative Biology (publishedVersion)
  • PubMed (publishedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
Funders
  • National Science Foundation (0330750, 9817138)
  • Earthwatch Institute
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › High Altitude and Hypoxia
  • Physical Sciences › Environmental Science › Ecology › Physiological and biochemical adaptations
  • Physical Sciences › Engineering › Aerospace Engineering › Biomimetic flight and propulsion mechanisms
Keywords
bird flight, high altitude, hypoxia, bird migration, wind speed, air density, oxygen partial pressure, hummingbirds, hovering flight, induced power, wing size, stroke amplitude, flight biomechanics, flight physiology, high-elevation birds

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