The energetics of hovering hummingbirds at altitude conditions

Berger, Martin

doi:10.1007/bf01644325

Cited by 34 publications

(10 citation statements)

References 20 publications

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“…Wing-beat frequencies of bar-headed geese in this study were similar in both normoxia and hypoxia. This is consistent with results from both ruby-throated hummingbirds ( Archilochus colubris ) and the South American hummingbird ( Colibri coruscans ), a montane species capable of hovering at altitudes over 6000m (Chai and Dudley, 1996; Berger, 1974). Despite a constant wing beat frequency, flight biomechanics of the geese in our study were altered in response to hypoxia, with increased upstroke duration (T) and decreased upstroke wingtip speed (Utip), upstroke plane amplitude (FSP), and mid-upstroke angle of inclination (a) (Supplementary file 4; Whale, 2012) As the downstroke produces the majority of lift and all forward thrust, by increasing the ratio of the duration of upstroke to downstroke, the duration of activation of the pectoralis major muscle group is decreased (responsible for the majority of downstroke power).…”

Section: Discussionsupporting

confidence: 89%

Reduced metabolism supports hypoxic flight in the high-flying bar-headed goose (Anser indicus)

Meir

York

Chua

et al. 2019

eLife

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The bar-headed goose is famed for migratory flight at extreme altitude. To better understand the physiology underlying this remarkable behavior, we imprinted and trained geese, collecting the first cardiorespiratory measurements of bar-headed geese flying at simulated altitude in a wind tunnel. Metabolic rate during flight increased 16-fold from rest, supported by an increase in the estimated amount of O2 transported per heartbeat and a modest increase in heart rate. The geese appear to have ample cardiac reserves, as heart rate during hypoxic flights was not higher than in normoxic flights. We conclude that flight in hypoxia is largely achieved via the reduction in metabolic rate compared to normoxia. Arterial Po2 was maintained throughout flights. Mixed venous PO2 decreased during the initial portion of flights in hypoxia, indicative of increased tissue O2 extraction. We also discovered that mixed venous temperature decreased during flight, which may significantly increase oxygen loading to hemoglobin.

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Section: Discussionsupporting

confidence: 89%

Reduced metabolism supports hypoxic flight in the high-flying bar-headed goose (Anser indicus)

Meir

York

Chua

et al. 2019

eLife

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“…This is predicted by aerodynamic theory for hovering animals (Ellington 1984), which says that the power requirements for hovering should increase as a function of decreasing air density. In laboratory studies, Berger (1974) observed an increase in oxygen consumption rate of 6%-8% when simulating a change in elevation between sea level and 4000 m in sparkling violetears (Colibri coruscans (Gould, 1846)) and glittering-throated hummingbirds. In the present study, we estimated a substantially greater increase in _ V _ O 2 hov =M b as a function of elevation in rufous hummingbirds.…”

Section: Discussionmentioning

confidence: 99%

Altitude and temperature effects on the energetic cost of hover-feeding in migratory rufous hummingbirds,Selasphorus rufus

Welch

Suarez

2008

Can. J. Zool.

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During migratory stopovers, rufous hummingbirds ( Selasphorus rufus (Gmelin, 1788)) can achieve high daily rates of net energy intake and mass gain while foraging at a range of elevations and ambient temperatures, despite the high energetic costs of hovering flight and thermoregulation. To gain insights into the factors affecting the energetic costs incurred during foraging, we captured migratory hummingbirds and measured their oxygen consumption rates during hover-feeding. Measurements were performed in situ where rufous hummingbirds forage as they migrate at several locations along a gradient in elevation and over the range of ambient temperatures normally experienced. Oxygen consumption rates during hover-feeding varied between the sexes and between juveniles and adults. These differences appeared to reflect differences in the power requirements for hovering flight in relation to variation in wing morphology. Decreasing ambient temperature and increasing elevation both significantly increased oxygen consumption rate during hover-feeding. The effects of these two environmental variables were additive, suggesting that hummingbird thermoregulatory requirements were not met by the additional heat produced by the higher metabolic rate necessary to support hovering flight at higher elevation. These results provide insight into the ways different foraging strategies may allow hummingbirds to maximize net energy intake.

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“…Kinematic and aerodynamic mechanisms of compensation for hypodense air have been studied under both laboratory and field conditions. Berger (1974a) experimentally imposed hypobaria on two species of montane hummingbirds, and elicited systematic increases in stroke amplitude and wing angle of attack, the latter parameter being estimated from horizontal projections of the wing chord. Manipulations of hovering flight in hummingbirds using hypodense helium mixtures under both normoxic and hypoxic conditions Dudley, 1995, 1996;Altshuler and Dudley, 2003) similarly revealed that low-density air elicits a systematic increase in stroke amplitude but essentially unchanged wingbeat frequencies.…”

Section: Hovering Flightmentioning

confidence: 99%

“…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 (see Ellington, 1984b). With the notable exception of Berger (1974a), effects of hypobaria on more detailed wingbeat kinematics such as angle of attack and rotational velocities at the ends of half-strokes are unstudied. Wingbeat kinematics of the Giant Andean Hummingbird are noticeably different at half-stroke transitions relative to those of other hummingbirds (M.-J.…”

Section: Hovering Flightmentioning

confidence: 99%

The physiology and biomechanics of avian flight at high altitude

Altshuler

2006

Integrative and Comparative Biology

100

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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.

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The energetics of hovering hummingbirds at altitude conditions

Cited by 34 publications

References 20 publications

Reduced metabolism supports hypoxic flight in the high-flying bar-headed goose (Anser indicus)

Reduced metabolism supports hypoxic flight in the high-flying bar-headed goose (Anser indicus)

Altitude and temperature effects on the energetic cost of hover-feeding in migratory rufous hummingbirds,Selasphorus rufus

The physiology and biomechanics of avian flight at high altitude

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