| 1. |
- Krishnan, Krishnamoorthy, et al.
(författare)
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The role of wingbeat frequency and amplitude in flight power
- 2022
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 19:193
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Tidskriftsartikel (refereegranskat)abstract
- Body-mounted accelerometers provide a new prospect for estimating power use in flying birds, as the signal varies with the two major kinematic determinants of aerodynamic power: wingbeat frequency and amplitude. Yet wingbeat frequency is sometimes used as a proxy for power output in isolation. There is, therefore, a need to understand which kinematic parameter birds vary and whether this is predicted by flight mode (e.g. accelerating, ascending/descending flight), speed or morphology. We investigate this using high-frequency acceleration data from (i) 14 species flying in the wild, (ii) two species flying in controlled conditions in a wind tunnel and (iii) a review of experimental and field studies. While wingbeat frequency and amplitude were positively correlated, R 2 values were generally low, supporting the idea that parameters can vary independently. Indeed, birds were more likely to modulate wingbeat amplitude for more energy-demanding flight modes, including climbing and take-off. Nonetheless, the striking variability, even within species and flight types, highlights the complexity of describing the kinematic relationships, which appear sensitive to both the biological and physical context. Notwithstanding this, acceleration metrics that incorporate both kinematic parameters should be more robust proxies for power than wingbeat frequency alone.
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| 2. |
- San-Jose, Luis M., et al.
(författare)
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Differential fitness effects of moonlight on plumage colour morphs in barn owls
- 2019
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Ingår i: Nature Ecology and Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 3:9, s. 1331-1340
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Tidskriftsartikel (refereegranskat)abstract
- The Moon cycle exposes nocturnal life to variation in environmental light. However, whether moonlight shapes the fitness of nocturnal species with distinct colour variants remains unknown. Combining data from long-term monitoring, high-resolution global positioning system tracking and experiments using prey, we show that barn owls (Tyto alba) with distinct plumage colourations are differently affected by moonlight. The reddest owls are less successful at hunting and providing food to their offspring during moonlit nights, which associates with lower body mass and lower survival of the youngest nestlings and with female mates starting to lay eggs at low moonlight levels. Although moonlight should make white owls more conspicuous to prey, it either positively affects or does not affect the hunting and fitness of the whitest owls. We experimentally show that, under full-moon conditions, white plumage triggers longer freezing times in prey, which should facilitate prey catchability. We propose that the barn owl’s white plumage, a rare trait among nocturnal predators, exploits the known aversion of rodents to bright light, explaining why, counterintuitively, moonlight has a lesser impact on the whitest owls. Our study provides evidence for the long-suspected influence of the Moon on the evolution of colouration in nocturnal species, highlighting the importance of colour in nocturnal ecosystems.
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