Biology subjects

Byholm, P.

Publications and source records attributed to Byholm, P..

4 recordsLinked to original sources

bioRxiv2025

Overcoming Innate Lateralization Improves Avian Flight Performance

Behavioural lateralization--side-bias or handedness--enhances neurological processing efficiency but creates a dilemma for behaviours requiring symmetry. Flight demands symmetric execution, particularly when optimising energy extraction from atmospheric updrafts during soaring. Using high-resolution biologging of 31 juvenile European honey buzzards from fledging through their first intercontinental migration leg, we show that strong lateralised circling was prevalent immediately after fledging (74%). This proportion declined to parity by migration onset, indicating developmental adjustment with increasing experience. During migration, side-biased circling was linked to wider turns, reduced altitude gain, and daily travel distances shortened by 13%. These findings reveal a direct trade-off between the neurological efficiency of lateralization and the aerodynamic requirements of efficient soaring. Our results challenge the notion that lateralization is universally adaptive and highlight how experience and ontogeny modulate the balance between task difficulty, neural specialization, and ecological performance.

animal behavior and cognition↗

bioRxiv2024

Natal dispersal and process of recruitment in a long-lived, trans-continentally migrating bird

Natal dispersal is a multi-step process. It commences when a juvenile departs from its natal site and concludes when it settles to breed for the first time. During this interim period, dispersing individuals of long-lived species undergo a wandering phase, which may span years. This phase remains one of the least studied aspects of species life history. We utilized a unique GPS-telemetry dataset on a slow-life history migratory bird of prey - the European honey buzzard, tracked for multiple years after fledgling. Our aim was to assess how phenology, ranging behaviour and philopatry change as individuals gain experience. Individuals exhibited variability in the age at which they first returned to their breeding range, yet all survivors settled at sites proximate to their natal nests. In subsequent returns, immatures increased the time spent within the breeding range and narrowed down their ranging to smaller areas situated even closer to their natal nests. Our study unveils the complexity and protraction inherent in natal dispersal, emphasizing the importance of individual experience and migratory improvement for successful recruitment in long-lived species. HIGHLIGHTSO_LIWe used a unique GPS telemetry dataset on honey buzzards to track their natal dispersal and recruitment in this long-lived avian migrant. C_LIO_LIAll individuals gradually decreased their ranging areas, moved closer to natal sites, and increased the time spent on the breeding grounds to synchronize with adults and begin recruitment. C_LIO_LIMortality during return migration was high and acted as a bottleneck. C_LIO_LIWe found both processes to be complex and lengthy, with the overall duration depending on individual decisions regarding the timing of return migration. C_LI

animal behavior and cognition↗

bioRxiv2022

Experience does not change the importance of wind support for migratory route selection by a soaring bird

Migration is a complex behavior that is costly in terms of time, energy, and risk of mortality. Thermal soaring birds rely on airflow, specifically wind support and uplift, to offset their energetic costs of flight. Their migratory routes are a record of movement decisions to negotiate the atmospheric environment and achieve efficiency. Because thermal soaring is a complex flight type that young birds need to learn, we expected that, as individuals gain more experience, their movement decisions will also increasingly favor the best thermal uplift conditions. We quantified how route choice during autumn migration of young European honey buzzards (Pernis apivorus) was adjusted to wind support and uplift over up to four years of migration and compared this to the choices of adult birds. We found that wind support was important in all migrations. However, we did not find an increase in the use of thermal uplifts, which could be an artifact of the uplift proxies that we used. Age-specific variations in response to airflow might occur at a smaller spatio-temporal scale than we investigated.

animal behavior and cognition↗

bioRxiv2019

Age-specific migration timing affects the energy seascape over an ecological barrier

Thermal soaring birds extract energy from the atmosphere to achieve energetically low-cost movement. When encountering regions that are energetically costly to fly over, such as open seas, they attempt to adjust the spatio-temporal pattern of their passage to maximize energy extraction from the atmosphere over these ecological barriers. We apply the concept of energy landscapes to investigate the spatio-temporal dynamics of energy availability over the open sea for soaring flight. We specifically investigated how the \"energy seascape\" may shape age-specific sea-crossing behaviour of European honey buzzards Pernis apivorus over the Mediterranean Sea in autumn. We found uplift potential over the sea to be the main determinant of sea-crossing length, rather than wind conditions. Considering this variable as a proxy for available energy over the sea, we constructed the energy seascape for the autumn migration season using forty years of temperature data. Our results indicate that early-migrating adult buzzards are likely to encounter adverse energy subsidence over the Mediterranean, whereas late-migrating juveniles face less adverse flight conditions, and even conditions conducive to soaring flight. Our study provides evidence that the dynamics of the energy landscape can explain intra-specific variation in migratory behaviour also at sea.

ecology↗