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Flight Energetics and the Aeroecology of a Soaring Scavenger

How do the largest birds move across the landscape in search of food while minimising their energy expenditure? Together, with Emily Shepard’s Flight team at SLAM (Swansea Laboratory for Animal Movement) and Sergio Lambertucci’s team, we are currently investigating the soaring strategy of the the Andean condor (Vultur gryphus) using high frequency bio-logging technology.

 
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Eavesdropping on Social Information in Soaring-Gliding Flight

Decisions of when and where to move to can have energetic consequences. Get the decision wrong and it can have energetic consequences. This is especially true for soaring birds that must glide between updrafts, where every second of gliding brings them closer to the ground? So how do they locate these invisible updrafts? In we tagged Gyps vultures (at Le Rocher des Aigles, France) flying in the same airspace to investigate whether they monitor the movements of others to gain information on updraft location; reducing uncertainty in movement and providing a mechanism by which large-scale networks may form in the sky.

Williams et al. (2018) Interface; The Conversation;

 
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Trade-offs in optimal currency through thermal climb: bank angle, turning radius and sink rate

Without flapping their wings a bird in flight will sink, so for birds that are too heavy to sustain flapping flight, how do they use exploit the lift available in updrafts to gain height without flapping? In this work we used high frequency loggers (Daily Diaries) to measure the bank angle (from magnetometry), turning radii (from airspeed sensors) and vertical velocity (from barametric pressure sensors) to parameterise concepts of aeronautical theory and investigate the soaring performance of Gyps vultures. We find that birds modify these parameters as they climb in thermal updrafts but with different trade-offs.

Williams et al. (2018) JEB

 
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Using Tri-axial Magnetometry to resolve animal movement patterns

Many bio-loggers are now equipped with magnetometer sensors, most commonly used for dead-reckoning movement tracks. But since tri-axial magnetometers resolve orientation of an animal relative to magnetic north, movement ecologists can use this information to quantify patterns of rotation and therefore identify and interpret behaviours; much in the same way as accelerometry, but there are instances when magnetometers can resolve behaviours that are not easily perceived using accelerometers…

Williams et al. (2017) Movement Ecology

 
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What can Acceleration tell us about the flight of Soaring Birds?

Accelerometers have proved to be extremely valuable movement sensors for the bio-logging world. But! the data they collect can be complex to interpret! This study was the first of my PhD, and used high-resolution movement data collected from soaring birds (condors and vultures) to examine the influence of gravitational, dynamic and centripetal acceleration on the output signal of an accelerometer in different flight types. Our work concludes that In the aerial environment movement may be influenced by phenomena such as pulling-g, making it difficult to interpret the output signal.

Williams et al. (2015) Animal Biotelemetry