Data from: Vultures respond to challenges of near-ground thermal soaring by varying bank angle

When using this dataset, please cite the original article.

Williams HJ, Duriez O, Holton MD, Dell-Omo G, Wilson RP, Shepard ELC (2018) Vultures respond to challenges of near-ground thermal soaring by varying bank angle. Journal of Experimental Biology: jeb.174995. doi:10.1242/jeb.174995

Additionally, please cite the Movebank data package:

Williams HJ, Shepard ELC, Duriez O (2018) Data from: Vultures respond to challenges of near-ground thermal soaring by varying bank angle. Movebank Data Repository. doi:10.5441/001/1.4f03k6s5
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Package Identifier doi:10.5441/001/1.4f03k6s5  
 
Abstract Many large birds rely on thermal soaring flight to travel cross-country. As such, they are under selective pressure to minimise the time spent gaining altitude in thermal updrafts. Birds should be able to maximise their climb rates by maintaining a position close to the thermal core through careful selection of bank angle and airspeed, however, there have been few direct measurements of either parameter. Here we apply a novel methodology to quantify the bank angles selected by soaring birds using on-board magnetometers. We couple these data with airspeed measurements to parameterise the soaring envelope of two species of Gyps vulture, from which it is possible to predict “optimal” bank angles. Our results show that these large birds respond to the challenges of gaining altitude in the initial phase of the climb, where thermal updrafts are weak and narrow, by adopting relatively high, and conserved, bank angles (25-35°). The angle of bank decreased with increasing altitude, in a manner that was broadly consistent with a strategy of maximising the rate of climb. However, the lift coefficients estimated in our study were lower than those predicted by theoretical models and wind-tunnel studies. Overall, our results highlight how the relevant currency for soaring performance changes within individual climbs; when thermal radius is limiting, birds vary bank angle and maintain a constant airspeed, but speed increases later in the climb in order to respond to decreasing air density.
Keywords aeroecology, airspeed, animal movement, animal tracking, gliding, GPS logger, griffon vulture, Gyps fulvus, Gyps himalayensis, Himalayan vulture, movement ecology, soaring, social information, vulture,

Gyps vultures with Pitot airspeed at Rocamadour (data from Williams et al. 2018) View File Details
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Download: Gyps vultures with Pitot airspeed at Rocamadour (data from Williams et al. 2018).csv ( 52.25Mb )
To the extent possible under law, the authors have waived all copyright and related or neighboring rights to this data.  



Gyps vultures with Pitot airspeed at Rocamadour (data from Williams et al. 2018)-reference-data View File Details
Download: README.txt ( 11.93Kb )
Download: Gyps vultures with Pitot airspeed at Rocamadour (data from Williams et al. 2018)-reference-data.csv ( 2.105Kb )
To the extent possible under law, the authors have waived all copyright and related or neighboring rights to this data.  


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