Coping with the commute: behavioural responses to wind conditions in a foraging seabird

• Published in: Journal of Avian Biology
• Main Authors: Collins, Philip M, Green, Jonathan A, Elliott, Kyle H, Shaw, Peter JA, Chivers, Lorraine, Hatch, Scott A, Halsey, Lewis G
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: rissa tridactyla; Alaska
• Online Access: http://livrepository.liverpool.ac.uk/3084555/; https://doi.org/10.1111/jav.02057; http://livrepository.liverpool.ac.uk/3084555/1/Accepted.pdf

Movement is a necessary yet energetically expensive process for motile animals. Yet how individuals modify their behaviour to take advantage of environmental conditions and hence optimise energetic costs during movement remains poorly understood. This is especially true for animals that move through environments where they cannot easily be observed. We examined the behaviour during commuting flights of black-legged kittiwakes Rissa tridactyla breeding on Middleton Island, Alaska in relation to wind conditions they face. By simultaneously deploying GPS and accelerometer devices on incubating birds we were able to quantify the timing, destination, course and speed of flights during commutes to foraging patches, as well as how wing beat frequency and strength relate to flight speeds. We found that kittiwakes did not preferentially fly in certain wind conditions. However, once in the air they exhibited plasticity through modulation of effort by increasing air speed (the speed at which they fly relative to the wind) when travelling into headwinds and decreasing their air speed when flying with tailwinds. Moreover, we identified a biomechanical link behind this behaviour: that to achieve these changes in flight speeds, kittiwakes altered their wing beat strength, but not wing beat frequency. Using this information, we demonstrate that the cost of flying into a headwind outweighs the energy saving benefit of flying with a tailwind of equivalent speed; therefore, exploiting a tailwind when commuting to a foraging patch would not be beneficial if having to return in the same direction with the same conditions. Our findings suggest that extrinsic factors, such as prey availability, have a more influential role in determining when and where kittiwakes fly during foraging trips than do wind conditions. However, once flying, kittiwakes exhibit behavioural plasticity to minimise transport costs.