Browsing by Author "Efrat, Ron"

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    Data from: Early life and acquired experiences interact in shaping migratory and flight behaviors
    (2023-11-21) Efrat, Ron; Hatzofe, Ohad; Mueller, Thomas; Sapir, Nir; Berger-Tal, Oded
    Two types of experience affect animals' behavioral proficiencies and accordingly their fitness: early-life experience–an animal’s environment during its early development, and acquired experience–the repeated practice of a specific task. Yet, how these two experience types and their interactions affect different proficiencies is still an open question. Here, we study the interactions between these two types of experience during migration, a critical and challenging period. We do so by comparing migratory proficiencies between birds with different early-life experiences, and explain these differences by testing fine-scale flight mechanisms. We used data collected by GPS transmitters during autumn migrations of 65 individuals to study the flight proficiencies of two groups of Egyptian vultures (Neophron percnopterus), a long-distance, soaring raptor. The two groups differed greatly in their early-life experience, one group being captive-bred and the other wild-hatched. Both groups improved their migratory performance with acquired experience, exhibiting shorter migration times, longer daily progress, and improved flight skills, specifically more efficient soaring-gliding behavior. The observed improvements were mostly apparent for captive-bred vultures which were the least efficient during their first migration but were able to catch up in their migratory performance already in the second migration. Thus, we show how the strong negative effects of early-life experience were offset by acquired experience. Our findings uncover how the interaction between early-life and acquired experiences may shape animals' proficiencies and shed new light on the ontogeny of animal migration, suggesting possible effects of sensitive periods of learning on the acquisition of migratory skills.
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    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.
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    Data from: The spatiotemporal properties of artificial feeding schemes influence the post-fledging movement of Egyptian Vultures
    (2024-03-13) Reznikov, Korin; Efrat, Ron; Berger-Tal, Oded; Sapir, Nir
    Many vulture populations have severely declined in the past decades, showing high juvenile mortality. To support these populations, feeding stations are used to increase food availability and to supply food without antibiotics and toxic compounds. Yet, supplying food at feeding stations may affect vulture behavior. We present a large-scale field experiment testing how different food provision schemes affected the movement of Egyptian Vultures (Neophron percnopterus). We used GPS transmitters harnessed to 18 vulture chicks and described their movements post-fledging. We categorized the vultures into 3 groups according to the feeding scheme used at feeding stations near their nests: frequent and spatially dispersed food supply (FD); non-frequent and spatially dispersed food supply (NFD); and frequent food supply, concentrated in one location (FC). We found that birds from all three groups increased their roosting distances from the nest with fledgling age, with the NFD and FC groups showing a greater increase than the FD group. Additionally, all 3 groups increased their daily flight distances, with the NFD group presenting the largest increase and the FD group presenting the smallest increase. Our findings offer new insights into the relevance of spatiotemporal differences in the management of feeding stations and show its effect on movement during birds’ early life stages, creating 2 main movement patterns: local and regional. Our findings can help decide upon the preferable feeding scheme in a way that will either encourage or reduce the early dispersal distances of fledglings, according to long- and short-term conservation objectives. For example, local movements during the post fledging period to known and stable food resources may reduce the risk of anthropogenic-induced mortality, while it may negatively affect long-term survival by hindering foraging, flight, and exploring skills and affect dispersion to future breeding sites.