![]() ![]() Although this framework was a remarkable advance for soaring flight research, the low spatial resolution of uplift estimates (0.3° in Bohrer et al. 26), which expanded its use in soaring flight studies (e.g. This method was later integrated with the track annotation tool of the online database MoveBank (, see ref. 16 presented an integrative method to produce estimates of orographic and thermal uplift from publically available meteorological and topographical data. In parallel, much progress has been made in modelling updrafts 12, 16, 19, 24, 25. refs 21 and 22), high-frequency tracking has recently helped to better understand the exact manoeuvring during soaring flight 7, 9, 11, 17, 23. While this variety of flight behaviours have been described for some decades from direct observations and radar tracking (e.g. Thermal soaring is typically divided in two phases, the circling phase where birds climb thermals in a circular ascending trajectory, and the gliding phase, where they achieve horizontal progression by descending in a linear trajectory 20, 21. Thermals are normally scattered across the landscape, but they may align densely in thermal streets 20. Thermals are formed when low masses of air get in contact with solar exposed terrain, warm-up and rise to several hundreds of meters 16. In comparison, thermal soaring is more commonly used in flat areas 9, 17, but also occurs in steeper terrain 19. ![]() Birds are able to gain altitude from the windward side of slopes but are also able to soar along ridges disposed linearly, such as mountain ranges 17, 18. Slope soaring is a response to orographic uplift that forms when horizontal winds are deflected upwards by physical barriers, such as ridges or hills 9, 16. Within inland soaring flight, two behavioural modes are commonly observed, slope soaring and thermal soaring 15. ![]() Yet, flapping allows flying in a straight course towards the target, thus promoting faster progression than soaring 14. Flapping is energetically costly, and birds use it more often when uplift conditions are not adequate 11, 12, 13. A critical energetic balance determines the use of soaring or flapping flight. In general, overland soaring birds show stereotyped flight behaviour responses to uplift variation 8, 9, 10. Recording Global Positioning System (GPS) data in very high-frequency (>0.1 Hz) is a relatively new capability of tracking devices that has recently boosted the study of avian flight, particularly soaring flight (e.g. Similarly, the study of animal movement has evolved from the simple description of trajectories to highly sophisticated inference on behaviour and ecophysiology 2, 4. Since the development of satellite transmitters in the 1980s, a number of technical innovations have made tracking devices smaller, highly precise, longer lasting, and capable of collecting types of information beyond geographical position, such as body motion or heart rate 2, 3. Miniaturized bio-logging technology suitable to track individual animals in the wild has revolutionized animal ecology as a science, paving the way for “movement ecology” as a new field of research 1. We recommend the use of this methodological approach to improve environmental impact assessments of new wind-energy installations. We show that updraft maps produced from publically available data can be used to predict where soaring birds will concentrate their flight paths and how they will behave in flight. We found that birds perform circular soaring in areas of higher predicted thermal uplift and linear soaring in areas of higher predicted orographic uplift velocity. Thermal and orographic uplift velocities were modelled from publically available remote-sensing and meteorological data. Bird tracks were segmented and classified into flight modes from motion parameters. This region has a diverse topography and land cover, favouring a heterogeneous updraft spatial distribution. We caught 21 black kites ( Milvus migrans) and GPS-tracked them while flying over the Tarifa region, on the Spanish side of the Strait of Gibraltar. We combined high-frequency GPS animal tracking and fine-spatial-scale uplift modelling to establish a link between flight behaviour of soaring birds and the distribution of updrafts. Understanding how soaring birds use updrafts at small spatial scales is important to identify ecological constraints of movement, and may help to prevent conflicts between wind-energy development and the conservation of wildlife. ![]()
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