8 results on '"Ken Yoda"'
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2. Decision-rules for leaping Adélie penguins (Pygoscelis adeliae).
- Author
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Ken Yoda and Yan Ropert-Coudert
- Subjects
- *
PYGOSCELIS , *ADELIE penguin , *JUMPING , *SWIMMING , *PARABOLA - Abstract
Adélie penguins Pygoscelis adeliae were tested as to whether they jump with optimal energy efficiency when moving out of the sea to the land. Adélie penguins risk predation if the jump fails. Swimming penguins usually launch up the side of sea ice to a surface higher than sea level. Analysis of jumping behaviour recorded by a video camera showed that the trajectory of the centre of gravity of the birds during the aerial phase of jumping was parabolic, indicating that the success of landing depends on three parameters at the time of take-off from water: speed, angle and distance from the point of emergence to the ice edge. There was a negative relationship between distance and the take-off angle, suggesting that penguins adjust their take-off angle to the distance from the ice edge. The comparison among hypotheses revealed that penguins did not jump with optimal energy efficiency. Instead, they aimed for the refracted image of the edge of the cliff, which from underwater appears higher than it actually is. This direction-dependent rule seems to be more robust and reliable than the optimal energetic strategy. [ABSTRACT FROM AUTHOR] more...
- Published
- 2004
- Full Text
- View/download PDF
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3. Development of flight performance in the brown booby.
- Author
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Ken Yoda, Hiroyoshi Kohno, and Yasuhiko Naito
- Subjects
- *
BIRD flight , *BIRD watching , *BROWN booby , *BOOBIES (Birds) - Abstract
How do birds acquire flight skills after fledging? This issue is important, as it is closely related to variation in the duration of offspring care, the causes of which remain unknown. In this study, we raised hatchling brown boobies, Sula leucogaster, and attached an acceleration data logger to each bird at fledging to record its movements. This allowed us to quantify precisely the time spent flapping, gliding and resting. The duration of foraging trips and proportion of time spent gliding during flight increased with the number of days since fledging, whereas the proportion of time spent in flight decreased. This indicates that brown boobies gradually acquire efficient flight skills during the post-fledging period, which might be the proximate cause of the long post-fledging care period in this species. To the authors' knowledge, this is the first study to record precisely the ontogeny of flight behaviour in birds. [ABSTRACT FROM AUTHOR] more...
- Published
- 2004
- Full Text
- View/download PDF
4. MOVEMENTS AND ACTIVITY CHARACTERISTICS OF THE BROWN BOOBY SULA LEUCOGASTER DURING THE NON-BREEDING PERIOD.
- Author
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HIROYOSHI KOHNO, AKIRA MIZUTANI, KEN YODA, and TAKASHI YAMAMOTO
- Subjects
- *
TIME measurements , *PHENOLOGY - Abstract
As the availability of individual-based tracking has increased, our understanding of seabird distributions outside the breeding season has advanced for a variety of species, but remains comparatively limited for species inhabiting the tropics. In this study, we investigated the at-sea movement and activity of eight Brown Boobies Sula leucogaster during the non-breeding period using light-level geolocators. Boobies spent the non-breeding season in the western Pacific across a large geographical range; however, at a regional scale, there was variation among individuals in their use of wintering habitats, with areas 6 575 km apart between their northernmost (the East China Sea/Yellow Sea) and southernmost (northern New Guinea) destinations. Overall, during the non-breeding period, boobies spent 17.6 % ± 5.0 % of their time on the water during the day and 11.1 % ± 8.2 % of their time on the water at night. This low percentage of time spent on the water at night indicates that they may have rested on land or roosted on rocks, a behavior that might be an anti-predatory strategy. Although individuals exhibited spatiotemporal variations in their movements, all tracked birds were absent in the breeding region for periods of time coinciding with seasonal pulses of unfavorable local environmental conditions. This study is the first to explore individual-based at-sea movements and activity characteristics of Sula species during the non-breeding period. Our results provide insight into how breeding phenology relates to seasonal movements. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
5. Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction.
- Author
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Yoshinari Yonehara, Yusuke Goto, Ken Yoda, Yutaka Watanuki, Young, Lindsay C., Weimerskirch, Henri, Bost, Charles-André, and Katsufumi Sato
- Subjects
- *
MIGRATION flyways , *SEA birds , *GLOBAL Positioning System , *METEOROLOGY , *WIND speed - Abstract
Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These birdbased wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps. [ABSTRACT FROM AUTHOR] more...
- Published
- 2016
- Full Text
- View/download PDF
6. Pelagic seabirds reduce risk by flying into the eye of the storm.
- Author
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Lempidakis, Emmanouil, Shepard, Emily L. C., Ross, Andrew N., Sakiko Matsumoto, Shiho Koyama, Ichiro Takeuchi, and Ken Yoda
- Subjects
- *
STORMS , *EXTREME weather , *WINDSTORMS , *EYE tracking , *WIND speed - Abstract
Cyclones can cause mass mortality of seabirds, sometimes wrecking thousands of individuals. The few studies to track pelagic seabirds during cyclones show they tend to circumnavigate the strongest winds. We tracked adult shearwaters in the Sea of Japan over 11 y and found that the response to cyclones varied according to the wind speed and direction. In strong winds, birds that were sandwiched between the storm and mainland Japan flew away from land and toward the eye of the storm, flying within ≤30 km of the eye and tracking it for up to 8 h. This exposed shearwaters to some of the highest wind speeds near the eye wall (≤21 m s–1) but enabled them to avoid strong onshore winds in the storm’s wake. Extreme winds may therefore become a threat when an inability to compensate for drift could lead to forced landings and collisions. Birds may need to know where land is in order to avoid it. This provides additional selective pressure for a map sense and could explain why juvenile shearwaters, which lack a map sense, instead navigating using a compass heading, are susceptible to being wrecked. We suggest that the ability to respond to storms is influenced by both flight and navigational capacities. This may become increasingly pertinent due to changes in extreme weather patterns. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
7. BASAL METABOLIC RATE OF THE RHINOCEROS AUKLET CERORHINCA MONOCERATA, AS MEASURED USING RESPIROMETRY.
- Author
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MASAKI SHIRAI, MOTOHIRO ITO, KEN YODA, and YASUAKI NIIZUMA
- Subjects
- *
BASAL metabolism , *RHINOCEROS auklet , *ALCIDAE , *ENERGY consumption , *ISLANDS - Abstract
The article examines the basal metabolic rate (BMR) of the Rhinoceros Auklets Cerorhinca monocerata, which are medium-sized alcids that breed in the temperate waters in the northern Pacific, using respirometry. BMR is defined as the energy required by animals while at rest, and is used to calculate metabolic intensity and energy expenditure. The experiment was carried out at Teuri Island in Hokkaido, Japan from June 21 to July 3, 2010. more...
- Published
- 2013
8. How do biparental species optimally provision young when begging is honest?
- Author
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Masahiro Ogawa, Tatsuya Shiozaki, Masaki Shirai, Müller, Martina S., Maki Yamamoto, and Ken Yoda
- Subjects
- *
BEGGING , *CHICKS , *SEA birds , *WATER birds , *CALONECTRIS - Abstract
Offspring transmit signals to parents to communicate their resource demands. Parents interpret these signals and should adjust provisioning efforts to meet offspring demands but only to the point at which the benefits of enhanced offspring quality stops exceeding the increased costs to future reproduction. We investigated both proximate behavioral mechanisms in these interactions and ultimate-level decisions for total parental investment in streaked shearwaters Calonectris leucomelas by recording begging calls, monitoring parental attendance, and altering states of chicks by supplementing food. In our study, chicks seemed to honestly communicate satiety and body condition via begging. The parents, however, did not downwardly adjust feeding rates, meal sizes delivered to chicks, and total investment in nests in which chicks were regularly supplementary-fed partial meals. But on nights when both parents visited the nest, the second-arriving parents recognized that chicks had already received a full meal because they reduced the food they gave to chicks and also lengthened their subsequent foraging trip. Our findings therefore suggest that although chick begging appeared to reflect need, parents only responded to variation in begging that indicated that chicks had already received a full meal. In a simulation, we show that this strategy prevents parents from exceeding the optimal amount of parental investment. Their insensitivity to slightly reduced begging after partial meals caused them to exceed optimal investment in supplementary-fed nests, suggesting that parental investment is largely regulated by responses to feeding rate of the other parent rather than being fine-tuned to cues about body condition of chicks. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
- Full Text
- View/download PDF
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