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Extreme endurance migration: what is the limit to non-stop flight?

Hedenström A - PLoS Biol. (2010)

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Lund University, Lund, Sweden. anders.hedenstrom@teorekol.lu.se

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In the past year, Gill et al. have provided direct evidence that a shorebird, the Alaskan bar-tailed godwit (Limosa lapponica baueri) (Figure 1), makes its eight-day, 11,000-km autumn migration from Alaska to New Zealand in one step, with no stopovers to rest or refuel... To understand how the bar-tailed godwits manage their improbable journey, we first need to know the metabolic costs entailed in long-distance flight... One possibility is that godwits differ in their fuel consumption compared with other birds... Again, this is partly explained by shape differences as we go from small to large birds, but there are also likely to be additional factors that explain the divergence from theory... As Figure 4 indicates, the godwit falls on the low side, but it does not stand out as an extreme outlier compared with other species... Another important feature for extreme endurance is a well-streamlined body shape, which helps to reduce the drag created by the body... In the godwit study, transmitters were surgically implanted in females, thus the beneficial effect of the body's streamlining was not severely disrupted... Do they follow some travel-plan involving directional shifts or do they try to fly in a constant heading (a fixed compass bearing) from the site of departure by using local cues? At high latitudes, a constant compass direction (without re-setting their internal clock to local time) would allow birds to fly along “great circles” (Box 2, Figure 5) if the migration direction has an East–West component... It seems clear that figuring out the mechanisms birds use to navigate and orient during such marathon migrations—for example, what cues they use to maintain orientation during long-distance flights, how often they check the compass(es), and how and if they integrate available information—will require moving beyond the traditional laboratory-based paradigm of experimentally manipulating one cue at a time... Can we expect the bar-tailed godwit record of a 11,000-km non-stop flight to be broken? I would guess not, simply because the physical limitations of the Earth do not offer any combination of ecologically feasible breeding and wintering areas more distantly apart that would require longer flights... Hence, it seems likely that the Alaskan bar-tailed godwit will keep its position as the number one non-stop long-distance flyer... Even if it has now been confirmed that the bar-tailed godwits do perform mindboggling direct flights across the Pacific, and that we do not need to rethink our theories and assumptions about flight and endurance to explain it, these flights raise many new questions.

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Potential flight range in relation to relative fuel load (expressed as the ratio between fuel mass and lean body mass) for the bar-tailed godwit (blue curve) and the blackpoll warbler (red curve).See Box 1 for details.
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pbio-1000362-g003: Potential flight range in relation to relative fuel load (expressed as the ratio between fuel mass and lean body mass) for the bar-tailed godwit (blue curve) and the blackpoll warbler (red curve).See Box 1 for details.

Mentions: Once we know the rate of fuel (mass) consumption, we can then work out the possible duration of the flight, which multiplied with flight speed, gives the distance covered (the flight range). Even if the rate of fuel consumption is quite similar between the blackpoll warbler (Dendroica striata) and the godwit, their potential flight range deviates widely because the godwit flies almost twice as fast (Figure 3). According to aerodynamic theory, provided the relative fuel load (i.e., fat and protein stores) is the same, similarly shaped birds should have the same potential flight range irrespective of body size [14]. In real birds, however, this is not the case (Figure 3), because species differ in wing and body shape. For example, the aspect ratio (Box 2) is 5.8 for the blackpoll warbler and 9.3 for the larger godwit, respectively.


Extreme endurance migration: what is the limit to non-stop flight?

Hedenström A - PLoS Biol. (2010)

Potential flight range in relation to relative fuel load (expressed as the ratio between fuel mass and lean body mass) for the bar-tailed godwit (blue curve) and the blackpoll warbler (red curve).See Box 1 for details.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2864269&req=5

pbio-1000362-g003: Potential flight range in relation to relative fuel load (expressed as the ratio between fuel mass and lean body mass) for the bar-tailed godwit (blue curve) and the blackpoll warbler (red curve).See Box 1 for details.
Mentions: Once we know the rate of fuel (mass) consumption, we can then work out the possible duration of the flight, which multiplied with flight speed, gives the distance covered (the flight range). Even if the rate of fuel consumption is quite similar between the blackpoll warbler (Dendroica striata) and the godwit, their potential flight range deviates widely because the godwit flies almost twice as fast (Figure 3). According to aerodynamic theory, provided the relative fuel load (i.e., fat and protein stores) is the same, similarly shaped birds should have the same potential flight range irrespective of body size [14]. In real birds, however, this is not the case (Figure 3), because species differ in wing and body shape. For example, the aspect ratio (Box 2) is 5.8 for the blackpoll warbler and 9.3 for the larger godwit, respectively.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Lund University, Lund, Sweden. anders.hedenstrom@teorekol.lu.se

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

In the past year, Gill et al. have provided direct evidence that a shorebird, the Alaskan bar-tailed godwit (Limosa lapponica baueri) (Figure 1), makes its eight-day, 11,000-km autumn migration from Alaska to New Zealand in one step, with no stopovers to rest or refuel... To understand how the bar-tailed godwits manage their improbable journey, we first need to know the metabolic costs entailed in long-distance flight... One possibility is that godwits differ in their fuel consumption compared with other birds... Again, this is partly explained by shape differences as we go from small to large birds, but there are also likely to be additional factors that explain the divergence from theory... As Figure 4 indicates, the godwit falls on the low side, but it does not stand out as an extreme outlier compared with other species... Another important feature for extreme endurance is a well-streamlined body shape, which helps to reduce the drag created by the body... In the godwit study, transmitters were surgically implanted in females, thus the beneficial effect of the body's streamlining was not severely disrupted... Do they follow some travel-plan involving directional shifts or do they try to fly in a constant heading (a fixed compass bearing) from the site of departure by using local cues? At high latitudes, a constant compass direction (without re-setting their internal clock to local time) would allow birds to fly along “great circles” (Box 2, Figure 5) if the migration direction has an East–West component... It seems clear that figuring out the mechanisms birds use to navigate and orient during such marathon migrations—for example, what cues they use to maintain orientation during long-distance flights, how often they check the compass(es), and how and if they integrate available information—will require moving beyond the traditional laboratory-based paradigm of experimentally manipulating one cue at a time... Can we expect the bar-tailed godwit record of a 11,000-km non-stop flight to be broken? I would guess not, simply because the physical limitations of the Earth do not offer any combination of ecologically feasible breeding and wintering areas more distantly apart that would require longer flights... Hence, it seems likely that the Alaskan bar-tailed godwit will keep its position as the number one non-stop long-distance flyer... Even if it has now been confirmed that the bar-tailed godwits do perform mindboggling direct flights across the Pacific, and that we do not need to rethink our theories and assumptions about flight and endurance to explain it, these flights raise many new questions.

Show MeSH