Migration by soaring or flapping: numerical atmospheric simulations reveal that turbulence kinetic energy dictates bee-eater flight mode

Sapir, Nir; Horvitz, Nir; Wikelski, Martin; Avissar, Roni; Mahrer, Yitzhak; Nathan, Ran

doi:10.1098/rspb.2011.0358

Cited by 59 publications

(68 citation statements)

References 32 publications

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“…Recently, high-resolution atmospheric simulations have been applied to study how meteorological conditions may shape the soaring behaviour of migrating birds [10,15]. Our study demonstrates the advantages of using detailed atmospheric modelling and rigorously tests predictions related to the effects of external factors (wind vectors) on commuting flyers.…”

Section: Discussionmentioning

confidence: 95%

“…Model steps were calculated every minute, and modelled wind data were spatially and temporally matched to each bat's location and averaged over every 5 min of the bat's commuting flight. Because no wind data were available from the study area, we report error estimates from a different application of RAMS [15]. Based on these error estimates, 95% of the wind data estimates are within 0.7 m s 21 of their actual value, with up to 2.4 m s 21 difference under strong (8 m s 21 ) but rare winds.…”

Section: (B) Atmospheric Modellingmentioning

confidence: 99%

“…In addition, we calculated the relationship between bat ground speed and the crosswind and tailwind velocities to assess whether strong crosswinds and headwinds incurred slower progress towards the destination. To correct for the unequal sample size from different individuals, the data from each bat were weighted based on the inverse proportion of that bat's sample size from the total data from all the bats [15,34,35]. We additionally report the results of the unweighted regression.…”

Section: (C) Data Analysismentioning

confidence: 99%

“…The ability to correctly determine wind direction and speed is critical for inferring animal flight performance, because optimal movement in relation to wind may involve changes in airspeed (speed relative to air), and modulation of this response when the wind is blowing from different directions relative to the heading [13]. Consequently, wind must be estimated at high spatial and temporal resolution to match the relevant scales affecting the flying organisms [14], as has been successfully done in recent studies of bird migration [10,15].…”

Section: Introductionmentioning

confidence: 99%

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Commuting fruit bats beneficially modulate their flight in relation to wind

et al. 2014

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When animals move, their tracks may be strongly influenced by the motion of air or water, and this may affect the speed, energetics and prospects of the journey. Flying organisms, such as bats, may thus benefit from modifying their flight in response to the wind vector. Yet, practical difficulties have so far limited the understanding of this response for free-ranging bats. We tracked nine straw-coloured fruit bats (Eidolon helvum) that flew 42.5 + 17.5 km (mean + s.d.) to and from their roost near Accra, Ghana. Following detailed atmospheric simulations, we found that bats compensated for wind drift, as predicted under constant winds, and decreased their airspeed in response to tailwind assistance such that their groundspeed remained nearly constant. In addition, bats increased their airspeed with increasing crosswind speed. Overall, bats modulated their airspeed in relation to wind speed at different wind directions in a manner predicted by a two-dimensional optimal movement model. We conclude that sophisticated behavioural mechanisms to minimize the cost of transport under various wind conditions have evolved in bats. The bats' response to the wind is similar to that reported for migratory birds and insects, suggesting convergent evolution of flight behaviours in volant organisms.

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Section: Discussionmentioning

confidence: 95%

Section: (B) Atmospheric Modellingmentioning

confidence: 99%

Section: (C) Data Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Commuting fruit bats beneficially modulate their flight in relation to wind

et al. 2014

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“…[10][11][12]; but see [13] for an exception). However, it is long established that many species use multiple modes of subsidized flight [14].…”

Section: Introductionmentioning

confidence: 99%

Use of multiple modes of flight subsidy by a soaring terrestrial bird, the golden eagleAquila chrysaetos, when on migration

Katzner

Turk

Duerr

et al. 2015

J. R. Soc. Interface.

103

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Large birds regularly use updrafts to subsidize flight. Although most research on soaring bird flight has focused on use of thermal updrafts, there is evidence suggesting that many species are likely to use multiple modes of subsidy. We tested the degree to which a large soaring species uses multiple modes of subsidy to provide insights into the decision-making that underlies flight behaviour. We statistically classified more than 22 000 global positioning satellite-global system for mobile communications telemetry points collected at 30-s intervals to identify the type of subsidized flight used by 32 migrating golden eagles during spring in eastern North America. Eagles used subsidized flight on 87% of their journey. They spent 41.9% + 1.5 ( x + s:e:m:, range: 18-56%) of their subsidized northbound migration using thermal soaring, 45.2% + 2.1 (12-65%) of time gliding between thermals, and 12.9% + 2.2 (1-55%) of time using orographic updrafts. Golden eagles responded to the variable local-scale meteorological events they encountered by switching flight behaviour to take advantage of multiple modes of subsidy. Orographic soaring occurred more frequently in morning and evening, earlier in the migration season, and when crosswinds and tail winds were greatest. Switching between flight modes allowed migration for relatively longer periods each day and frequent switching behaviour has implications for a better understanding of avian flight behaviour and of the evolution of use of subsidy in flight.

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Environmental factors influencing red knot (Calidris canutus islandica) departure times of relocation flights within the non‐breeding period

Gobbens,

Beardsworth,

Dekinga

et al. 2024

Ecology and Evolution

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Deciding when to depart on long‐distance, sometimes global, movements can be especially important for flying species. Adverse weather conditions can affect energetic flight costs and navigational ability. While departure timings and conditions have been well‐studied for migratory flights to and from the breeding range, few studies have focussed on flights within the non‐breeding season. Yet in some cases, overwintering ranges can be large enough that ecological barriers, and a lack of resting sites en route, may resist movement, especially in unfavorable environmental conditions. Understanding the conditions that will enable or prohibit flights within an overwintering range is particularly relevant in light of climate change, whereby increases in extreme weather events may reduce the connectivity of sites. We tracked 495 (n = 251 in 2019; n = 244 in 2020) overwintering red knots (Calidris canutus islandica) in the Dutch Wadden Sea and investigated how many departed towards the UK (on westward relocation flights), which requires flying over the North Sea. For those that departed, we used a resource selection model to determine the effect of environmental conditions on the timing of relocation flights. Specifically, we investigated the effects of wind, rain, atmospheric pressure, cloud cover, and migratory timing relative to sunset and tidal cycle, which have all been shown to be crucial to migratory departure conditions. Approximately 37% (2019) and 36% (2020) of tagged red knots departed on westward relocation flights, indicating differences between individuals' space use within the overwintering range. Red knots selected for departures between 1 and 2.5 h after sunset, approximately 4 h before high tide, with tailwinds and little cloud cover. However, rainfall and changes in atmospheric pressure appear unimportant. Our study reveals environmental conditions that are important for relocation flights across an ecological barrier, indicating potential consequences of climate change on connectivity.

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Migration by soaring or flapping: numerical atmospheric simulations reveal that turbulence kinetic energy dictates bee-eater flight mode

Cited by 59 publications

References 32 publications

Commuting fruit bats beneficially modulate their flight in relation to wind

Commuting fruit bats beneficially modulate their flight in relation to wind

Use of multiple modes of flight subsidy by a soaring terrestrial bird, the golden eagleAquila chrysaetos, when on migration

Environmental factors influencing red knot (Calidris canutus islandica) departure times of relocation flights within the non‐breeding period

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