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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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Two hypothetical scenarios about the evolution of long-distance migration in bar-tailed godwits breeding in Alaska.(Top) A breeding range expansion with maintained migration direction but increased distances. (Bottom) An increased migration direction paired with shifted migration distance.
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pbio-1000362-g006: Two hypothetical scenarios about the evolution of long-distance migration in bar-tailed godwits breeding in Alaska.(Top) A breeding range expansion with maintained migration direction but increased distances. (Bottom) An increased migration direction paired with shifted migration distance.

Mentions: Why long-distance migration evolves in the first place is a complex question [30], and the trans-oceanic flights of Alaskan bar-tailed godwits represent one extreme end of the spectrum. It is unlikely that naïve short distance migratory birds accidentally reached New Zealand to establish this migration route, since that would have required excessive “incidental” fat deposits to keep them going for the duration of the flight. Hudsonian godwits (Limosa haemastica) do however visit New Zealand occasionally, but these are already long-distance migrants (albeit less than the bar-tailed godwit) with wintering areas in southern South America and have probably accompanied flocks of bar-tailed godwits in Alaska [12]. As with other seemingly improbable adaptations, it is most likely that the Alaska–New Zealand autumn migration route evolved gradually (Figure 6). One hypothetical scenario is that there was already a long-distance migrating population breeding in Central Siberia and wintering in South Asia. The population expanded towards the east while prolonging its migration, initially via wintering sites on the Philippines, the Indonesian islands and/or New Guinea, Australia and eventually reaching New Zealand (Figure 6A). A second scenario assumes an Alaskan breeding population with a short-range migration to wintering sites in Northeast Asia gradually extending to South Asia. As long-distance migration between Alaska and South Asia became more common, a continuous shift of the migrants to wintering sites further to the east and south eventually established a direct flight route to New Zealand (Figure 6B). Mapping the historical distribution of bar-tailed godwits with molecular genetic information could perhaps resolve whichever of these, or other scenarios, is the most likely candidate. During spring, the godwits split their migration in at least two stages via a detour to East Asia, having a staging post in the Yellow Sea area, before flying to the breeding areas in Alaska. This looped migration argues in favor of scenario two (Figure 6B) and for the evolution of a direct migration route in the autumn.


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

Hedenström A - PLoS Biol. (2010)

Two hypothetical scenarios about the evolution of long-distance migration in bar-tailed godwits breeding in Alaska.(Top) A breeding range expansion with maintained migration direction but increased distances. (Bottom) An increased migration direction paired with shifted migration distance.
© Copyright Policy
Related In: Results  -  Collection

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

pbio-1000362-g006: Two hypothetical scenarios about the evolution of long-distance migration in bar-tailed godwits breeding in Alaska.(Top) A breeding range expansion with maintained migration direction but increased distances. (Bottom) An increased migration direction paired with shifted migration distance.
Mentions: Why long-distance migration evolves in the first place is a complex question [30], and the trans-oceanic flights of Alaskan bar-tailed godwits represent one extreme end of the spectrum. It is unlikely that naïve short distance migratory birds accidentally reached New Zealand to establish this migration route, since that would have required excessive “incidental” fat deposits to keep them going for the duration of the flight. Hudsonian godwits (Limosa haemastica) do however visit New Zealand occasionally, but these are already long-distance migrants (albeit less than the bar-tailed godwit) with wintering areas in southern South America and have probably accompanied flocks of bar-tailed godwits in Alaska [12]. As with other seemingly improbable adaptations, it is most likely that the Alaska–New Zealand autumn migration route evolved gradually (Figure 6). One hypothetical scenario is that there was already a long-distance migrating population breeding in Central Siberia and wintering in South Asia. The population expanded towards the east while prolonging its migration, initially via wintering sites on the Philippines, the Indonesian islands and/or New Guinea, Australia and eventually reaching New Zealand (Figure 6A). A second scenario assumes an Alaskan breeding population with a short-range migration to wintering sites in Northeast Asia gradually extending to South Asia. As long-distance migration between Alaska and South Asia became more common, a continuous shift of the migrants to wintering sites further to the east and south eventually established a direct flight route to New Zealand (Figure 6B). Mapping the historical distribution of bar-tailed godwits with molecular genetic information could perhaps resolve whichever of these, or other scenarios, is the most likely candidate. During spring, the godwits split their migration in at least two stages via a detour to East Asia, having a staging post in the Yellow Sea area, before flying to the breeding areas in Alaska. This looped migration argues in favor of scenario two (Figure 6B) and for the evolution of a direct migration route in the autumn.

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