The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

Nourani, Elham; Bohrer, Gil; Becciu, Paolo; Bierregaard, Richard O.; Duriez, Olivier; Figuerola, Jordi; Gangoso, Laura; Giokas, Sinos; Higuchi, Hiroyoshi; Kassara, Christina; Kulikova, Olga; Lecomte, Nicolas; Monti, Flavio; Pokrovsky, Ivan; Sforzi, Andrea; Therrien, Jean‐François; Tsiopelas, Nikos; Vansteelant, Wouter M. G.; Viana, Duarte S.; Yamaguchi, Nori; Wikelski, Martin; Safi, Kamran

doi:10.1101/2020.09.04.282939

Cited by 11 publications

(13 citation statements)

References 60 publications

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“…Data accessibility. All data used in this study are available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.r4xgxd2ct [61]. R codes are available at https://github.com/mahle68/global_ seascape_public.…”

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The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

et al. 2021

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Flying over the open sea is energetically costly for terrestrial birds. Despite this, over-water journeys of many birds, sometimes hundreds of kilometres long, are uncovered by bio-logging technology. To understand how these birds afford their flights over the open sea, we investigated the role of atmospheric conditions, specifically wind and uplift, in subsidizing over-water flight at a global scale. We first established that Δ T , the temperature difference between sea surface and air, is a meaningful proxy for uplift over water. Using this proxy, we showed that the spatio-temporal patterns of sea-crossing in terrestrial migratory birds are associated with favourable uplift conditions. We then analysed route selection over the open sea for five facultative soaring species, representative of all major migratory flyways. The birds maximized wind support when selecting their sea-crossing routes and selected greater uplift when suitable wind support was available. They also preferred routes with low long-term uncertainty in wind conditions. Our findings suggest that, in addition to wind, uplift may play a key role in the energy seascape for bird migration that in turn determines strategies and associated costs for birds crossing ecological barriers such as the open sea.

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The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

et al. 2021

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“…In highly specialised soaring species, considering the link between biogeography and movement only in relation to colonization would underestimate the role of uplifts as essential part of the niche of these species, for which uplifts should be considered among the suite of resources they need in order to exist in a certain area. Long accepted definitions of ecological barriers such as water bodies for soaring birds, are now being revisited as more flexible than previously thought (Nourani et al 2020), and should be adapted to accommodate the diversity in movement capacity among species.…”

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The species-specificity of energy landscapes for soaring birds, and its consequences for transferring suitability models across species

Scacco

Arrondo

Donázar

et al. 2021

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Soaring birds use the energy available in the environment in the form of atmospheric uplifts, to subsidize their flight. Their dependence on soaring opportunities makes them extremely sensitive to anthropogenic wind energy development. Predictive modelling is now considered instrumental to forecast the impact of wind farms on single species of concern. However, as multiple species often coexist in the same area, there is clear need to overcome the limitations of single species approaches. We looked for converging patterns in the way two obligate soaring species use the energy available in the landscape to soar, using movement data from 57 white storks, Ciconia ciconia, and 27 griffon vultures, Gyps fulvus. We first compared the soaring efficiency of the two species. We then tested the accuracy of topographic features, important correlates of collision risk in soaring birds, in predicting their soaring behaviour. We finally tested the transferability of soaring suitability models across species. Topography alone can predict and map the soaring opportunities available to storks across Europe, but not as efficiently in vultures. Only 20.5% of the study area was suitable to both species to soar, suggesting the existence of species-specific requirements in the use of the landscape for soaring. Storks relied on uplift occurrence while vultures on uplift quality, needing stronger uplifts to support their higher body mass and wing loading. Our results indicate that the flight of highly specialized soaring species is more dependent on atmospheric conditions than on static features, and that more knowledge is required to accurately predict their behaviour. Despite the superficially similar soaring behaviour, the two species have different environmental requirements, suggesting that energy landscapes are species-specific. Our models provide a base to explore the effects that changes in the landscape have on the flight behaviour of different soaring species and suggest that there is no reliable and responsible way to shortcut risk assessment in areas where multiple species might be at risk by anthropogenic structures.

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“…This may serve as an advantage particularly over ecological barriers such as the Sahara Desert where birds are at higher risk of evaporative water loss during the day [32,33]. Purple martins may also select barrier crossing ights at night to confer other advantages, such as cooler temperatures, lighter winds, or other environmental factors such as reduced predation that may facilitate open-water crossing at night [34]. The migration speeds we measured for purple martins support this, where rates were highest when they were making open water crossings over the Caribbean Sea (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…However, regardless of wind factors, almost all instances of a bird reorienting to circumnavigate occurred during nighttime segments, and most water crossings were initiated during the day, suggesting that initiating water crossing at night is not generally favoured. Recent investigation has revealed that seascapes may provide energetic advantages through a combination of uplift and/or wind conditions ("energy seascape", [34,37]). While these advantages would apply the most to birds using soaring ight, our results suggest that birds may make crossing decisions based upon the energetics of the seascape.…”

Section: Discussionmentioning

confidence: 99%

The Use of Nocturnal Flights for Barrier Crossing in a Diurnally Migrating Songbird: Implications for Our Understanding of Fly-and-Forage Migration Strategies

Lavallée¹,

Assadi²,

Korpach³

et al. 2020

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Background: The migration patterns of land birds can generally be divided into those species that migrate principally during the day and those that migrate during the night. Some species may show individual plasticity in the use of day or night flight, particularly when crossing large, open-water or desert barriers. However, individual plasticity in circadian patterns of migratory flights in diurnal songbirds that use a fly-and-forage migration strategy has never been investigated. Methods: We used high precision GPS tracking of a diurnal, migratory swallow Purple martin, (Progne subis), to determine whether individuals were flexible in their spring migration strategies to include some night flight, particularly at barrier crossing.Results: We found that individuals made large (sometimes >1000 km), open-water crossings of the Caribbean Sea and the Gulf of Mexico that included the use of night flight. Some birds-initiated barrier crossing flights at night, demonstrating that night flight is not only used to complete barrier crossings but may confer other advantages for diurnal birds. All birds also used some, shorter night flights when making overland flights not associated with barrier crossing. Birds were more likely to initiate water crossings with supportive northward winds, and preliminary data suggest that moonlight may influence nighttime migratory movements.Conclusions: Overall, our results demonstrate an unexpected high degree of individual plasticity in migration strategies on a circadian scale in a ‘diurnal’ songbird and suggest that barrier crossing at night may complement fly-and-forage migration strategies.

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The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

Cited by 11 publications

References 60 publications

The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

The species-specificity of energy landscapes for soaring birds, and its consequences for transferring suitability models across species

The Use of Nocturnal Flights for Barrier Crossing in a Diurnally Migrating Songbird: Implications for Our Understanding of Fly-and-Forage Migration Strategies

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