Browsing by Author "Quetting, Michael"
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- Data packageData from: Dynamic body acceleration increases by 20% during flight ontogeny of greylag geese (Anser anser)(2019-11-15) Gatt, Marie Claire; Quetting, Michael; Cheng, Yachang; Wikelski, MartinDespite our knowledge of the biophysical and behavioural changes during flight ontogeny in juvenile birds, little is known about the changes in the mechanical aspects of energy expenditure during early flight development, particularly in migratory species. Here, we investigate in a unique experimental setup how energy expended during flights changes over time beginning with early ontogeny. We calculate overall dynamic body acceleration (ODBA) as a proxy for energy expenditure in a group of hand raised Greylag Geese (Anser anser) trained to fly behind a microlight aircraft. We propose two potential hypotheses; energy expenditure either increases with increasing physiological suitability (the ‘physical development hypothesis’), or decreases as a result of behavioural improvements mitigating flight costs (the ‘behavioural development hypothesis’). There was a significant temporal increase of flight duration and ODBA over time, supporting the ‘physical development hypothesis’. This suggests that early on in flight ontogeny behavioural development leading to flight efficiency plays a weaker role in shaping ODBA changes than the increased physical ability to expend energy in flight. We discuss these findings and the implications of flight development on the life history of migratory species.
- Data packageData from: Study "LifeTrack White Stork SW Germany" (2013-2023)(2024-01-17) Fiedler, Wolfgang; Flack, Andrea; Schäfle, Wolfgang; Keeves, Brigitta; Quetting, Michael; Eid, Babette; Schmid, Heidi; Wikelski, MartinHuman-induced changes in climate and environment are challenging the existence of migratory species. Species with diverse and flexible migratory behaviour suffer less from population decline, as they are more capable to respond by altering migratory behaviour. At the individual-level, variations in migratory behaviour may lead to differences in fitness and subsequently influence demographic dynamics. Using lifetime GPS bio-logging data from 169 white storks (Ciconia ciconia), we answer whether their recently shortened migration has survival benefit during the juvenile stage, the riskiest life period for many migrants. We also explore how other variations in migratory decisions (i.e. time, destination), movement activity (measured by the overall body dynamic acceleration), and early life conditions influence juveniles’ survival. We observed that first autumn migration was the riskiest period for juvenile white storks. Individuals that migrated shorter distances and fledged earlier experienced lower mortality risk. In addition, higher movement activity and overwintering “closer-to-home” in Europe and North Africa (84.21% of tracked individuals adopted this new strategy) were associated with higher survival. Our study shows how avian migrants can change life history decisions linked to fitness over few decades and thus helps us to understand and predict how migrants respond to the changing world.
- Data packageData from: Turbulence causes kinematic and behavioural adjustments in a flapping flier(2024-02-20) Lempidakis, Emmanouil; Ross, Andrew N.; Quetting, Michael; Krishnan, Krishnamoorthy; Garde, Baptiste; Wikelski, Martin; Shepard, Emily L.C.Turbulence is a widespread phenomenon in the natural world, but its influence on flapping fliers remains little studied. We assessed how freestream turbulence affected the kinematics, flight effort, and track properties of homing pigeons (Columba livia), using the fine-scale variations in flight height as a proxy for turbulence levels. Birds showed a small increase in their wingbeat amplitude with increasing turbulence (similar to laboratory studies), but this was accompanied by a reduction in mean wingbeat frequency, such that their flapping wing speed remained the same. Mean kinematic responses to turbulence may therefore enable birds to increase their stability without a reduction in propulsive efficiency. Nonetheless, the most marked response to turbulence was an increase in the variability of wingbeat frequency and amplitude. These stroke-to-stroke changes in kinematics provide instantaneous compensation for turbulence. They will also increase flight costs. Yet pigeons only made small adjustments to their flight altitude, likely resulting in little change in exposure to strong convective turbulence. Responses to turbulence were therefore distinct from responses to wind, with the costs of high turbulence being levied through an increase in the variability of their kinematics and airspeed. This highlights the value of investigating the variability in flight parameters in free-living animals.