Sensor:
Acceleration

No Thumbnail Available
Name
Acceleration
External ID
acceleration
Is Location Sensor

Filters

2015 - 20196
Reset filters

Settings

Subject: avian migration × Start date: 2015 × End date: 2019 ×

Search Results

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Data package
    Data from: Landscape-dependent time versus energy optimisations in pelicans migrating through a large ecological barrier
    (2019-08-08) Efrat, Ron; Hatzofe, Ohad; Nathan, Ran
    1. During migration, birds are often forced to cross ecological barriers, facing challenges due to scarcity of resources and suitable habitats. While crossing such barriers, birds are expected to adjust their behaviour to reduce time, energy expenditure and associated risks. 2. We studied the crossing of the Sahara Desert by the Great White Pelican (Pelecanus onocrotalus), a large wetland‐specialist. We focused on decisions made by migrating pelicans along different parts of the southbound autumn migration, their response to local environmental conditions, and the implications for time and energy optimisations. We compared the observed pelicans' migration routes with simulated “direct‐pass” (shortest, mostly across the desert) and “corridor‐pass” (along the Nile River) routes, and used GPS, body acceleration and atmospheric modelling to compare flight behaviour along the Nile River versus the desert. 3. The observed route was significantly shorter and faster than the simulated corridor‐pass route and not significantly different from the simulated direct‐pass one. Daily flights over the desert were longer than along the Nile River, with flying time extending to late hours of the day despite unfavourable atmospheric conditions for soaring‐gliding flight. Moreover, the pelicans behavioural response to atmospheric conditions changed according to the landscape over which they flew. Overall, the pelicans showed stronger behavioural adjustments to atmospheric conditions over the desert than along the Nile River. 4. Our findings suggest that migrating pelicans primarily acted as time minimisers while crossing the Sahara Desert, whereas energetic optimisation was only considered when it did not substantially compromise time optimisation. The pelicans took the almost shortest possible route, only following the Nile River along its south‐oriented parts, and frequently staged overnight in the desert far from water, despite being large, wet‐habitat specialists. Correspondingly, their behavioural response to atmospheric conditions changed according to the landscape over which they were flying, switching between time (over the desert) and energy (over the Nile River) optimisation strategies. Our results suggest that the interaction between landscape and atmospheric conditions depict a flexible, yet primarily time‐dominated, migration optimisation strategy.
  • No Thumbnail Available
    Data package
    Data from: Overall dynamic body acceleration in straw-colored fruit bats increases in headwinds but not with airspeed
    (2019-05-21) Scharf, Anne K.; Fahr, Jakob; Abedi-Lartey, Michael; Safi, Kamran; Dechmann, Dina K.N.; Wikelski, Martin; O'Mara, M. Teague
    Atmospheric conditions impact how animals use the aerosphere, and birds and bats should modify their flight to minimise energetic expenditure relative to changing wind conditions. To investigate how free-ranging straw-colored fruit bats (Eidolon helvum) fly with changing wind support, we use data collected from bats fit with GPS loggers and an integrated triaxial accelerometer and measure flight speeds, wingbeat frequency, and overall dynamic body acceleration (ODBA) as an estimate for energetic expenditure. We predicted that if ODBA reflects energetic expenditure, then we should find a curvilinear relationship between ODBA and airspeed consistent with aerodynamic theory. We expected that bats would lower their airspeed with tailwind support and that ODBA will decrease with increasing tailwinds and increase with wingbeat frequency. We found that wingbeat frequency has the strongest positive relationship with ODBA. There was a small, but negative, relationship between airspeed and ODBA, and bats decreased ODBA with increasing tailwind. Bats flew at ground speeds of 9.6 ± 2.4 ms-1 (mean ± sd, range: 4.3 to 23.9 ms-1) and airspeeds of 10.2 ± 2.5 ms-1, and did not modify their wingbeat frequency with speed. Free-ranging straw-colored fruit bats therefore exerted more total ODBA in headwinds but not when they changed their airspeed. It is possible that the flexibility in wingbeat kinematics may make flight of free-ranging bats less costly than currently predicted or alternatively that the combination of ODBA and airspeed at our scales of measurement does not reflect this relationship in straw-colored fruit bats. Further work is needed to understand the full potential of free-ranging bat flight and how well bio-logging techniques reflect the costs of bat flight.
  • No Thumbnail Available
    Data package
    Data from: The challenges of the first migration: movement and behavior of juvenile versus adult white storks with insights regarding juvenile mortality
    (2016-04-12) Rotics, Shay; Kaatz, Michael; Resheff, Yehezkel S.; Turjeman, Sondra Feldman; Zurell, Damaris; Sapir, Nir; Eggers, Ute; Flack, Andrea; Fiedler, Wolfgang; Jeltsch, Florian; Wikelski, Martin; Nathan, Ran
    (1) Migration conveys an immense challenge especially for juvenile birds coping with enduring and risky journeys shortly after fledging. Accordingly, juveniles exhibit considerably lower survival rates compared to adults, particularly during migration. Also, juvenile white storks (Ciconia ciconia), which are known to rely on adults during their first fall migration, presumably for navigational purposes, display much lower annual survival than adults. (2) Using detailed GPS and body acceleration data, we examined the patterns and potential causes of age-related differences in fall migration properties of white storks by comparing first-year juveniles and adults. We compared juvenile and adult parameters of movement, behavior and energy expenditure (estimated from overall dynamic body acceleration, ODBA) and placed this in the context of the juveniles’ lower survival rate. (3) Juveniles used flapping flight versus soaring flight 23% more than adults and were estimated to expend 14% more energy during flight. Juveniles did not compensate for increased flight costs by increased refueling or resting during migration. When juveniles and adults migrated together in the same flock, the juvenile flew mostly behind the adult and was left behind when they separated. Juveniles showed greater improvement in flight efficiency throughout migration compared to adults which appears crucial because juveniles exhibiting higher flight costs suffered increased mortality. (4) Our findings demonstrate the conflict between the juveniles’ inferior flight skills and their urge to keep up with mixed adult-juvenile flocks. We suggest that increased flight costs are an important proximate cause of juvenile mortality in white storks and likely in other soaring migrants, and that natural selection is operating on juvenile variation in flight efficiency.
  • No Thumbnail Available
    Data package
    Data from: Costs of migratory decisions: a comparison across eight white stork populations
    (2015-06-13) Flack, Andrea; Fiedler, Wolfgang; Blas, Julio; Pokrovsky, Ivan; Mitropolsky, B.; Kaatz, Michael; Aghababyan, Karen; Khachatryan, A.; Fakriadis, Ioannis; Makrigianni, Eleni; Jerzak, Leszek; Shamin, M.; Shamina, C.; Azafzaf, H.; Mokotjomela, Thabiso M.; Feltrup-Azafzaf, Claudia; Wikelski, Martin
    Annual migratory movements can range from a few tens to thousands of kilometers, creating unique energetic requirements for each specific species and journey. Even within the same species, migration costs can vary largely because of flexible, opportunistic life history strategies. We uncover the large extent of variation in the lifetime migratory decisions of young white storks originating from eight populations. Not only did juvenile storks differ in their geographically distinct wintering locations, their diverse migration patterns also affected the amount of energy individuals invested for locomotion during the first months of their life. Overwintering in areas with higher human population reduced the stork’s overall energy expenditure because of shorter daily foraging trips, closer wintering grounds, or a complete suppression of migration. Because migrants can change ecological processes in several distinct communities simultaneously, understanding their life history decisions helps not only to protect migratory species but also to conserve stable ecosystems.
  • No Thumbnail Available
    Data package
    Data from: Early arrival at breeding grounds: causes, costs and a trade-off with overwintering latitude
    (2018-09-14) Rotics, Shay; Kaatz, Michael; Turjeman, Sondra Feldman; Zurell, Damaris; Wikelski, Martin; Sapir, Nir; Eggers, Ute; Fiedler, Wolfgang; Jeltsch, Florian; Nathan, Ran
    (1) Early arrival at breeding grounds is of prime importance for migrating birds as it is known to enhance breeding success. Adults, males and higher quality individuals typically arrive earlier, and across years, early arrival has been linked to warmer spring temperatures. However, the mechanisms and potential costs of early arrival are not well understood. (2) To deepen the understanding of arrival date differences between individuals and years, we studied them in light of the preceding spring migration behaviour and atmospheric conditions en route. (3) GPS and body‐acceleration (ACC) data were obtained for 35 adult white storks (Ciconia ciconia) over five years (2012‐2016). ACC records were translated to energy expenditure estimates (Overall Dynamic Body Acceleration; ODBA) and to behavioural modes, and GPS fixes were coupled with environmental parameters. (4) At the inter‐individual level (within years), early arrival was attributed primarily to departing earlier for migration and from more northern wintering sites (closer to breeding grounds), rather than to migration speed. In fact, early departing birds flew slower, experienced weaker thermal uplifts and expended more energy during flight, but still arrived earlier, emphasizing the cost and the significance of early departure. Individuals that wintered further south arrived later at the breeding grounds but did not produce fewer fledglings, presumably due to positive carry‐over effects of advantageous wintering conditions (increased precipitation, vegetation productivity and daylight time). Therefore, early arrival increased breeding success only after controlling for wintering latitude. Males arrived slightly ahead of females. Between years, late arrival was linked to colder temperatures en route through two different mechanisms: stronger headwinds causing slower migration and lower thermal uplifts resulting in longer stopovers. (5) This study showed that distinct migratory properties underlie arrival time variation within and between years. It highlighted: (a) an overlooked cost of early arrival induced by unfavourable atmospheric conditions during migration, (b) an important fitness trade‐off in storks between arrival date and wintering habitat quality, and (c) mechanistic explanations for the negative temperature‐arrival date correlation in soaring birds. Such understanding of arrival time can facilitate forecasting migrating species responses to climate changes.
  • No Thumbnail Available
    Data package
    Data from: Behavioural adaptations to flight into thin air
    (2016-10-24) Sherub, Sherub; Wikelski, Martin; Fiedler, Wolfgang; Davidson, Sarah C.
    Soaring raptors can fly at high altitudes of up to 9000 m. The behavioural adjustments to high-altitude flights are largely unknown. We studied thermal- ling flights of Himalayan vultures (Gyps himalayensis) from 50 to 6500 m above sea level, a twofold range of air densities. To create the necessary lift to support the same weight and maintain soaring flight in thin air birds might modify lift coefficient by biophysical changes, such as wing posture and increasing the power expenditure. Alternatively, they can change their flight characteristics. We show that vultures use the latter and increase circle radius by 35% and airspeed by 21% over their flight altitude range. These simple behavioural adjustments enable vultures to move seamlessly during their annual migrations over the Himalaya without increasing energy output to flight in high elevations.