Le lundi 25 novembre 2019 à 11h, Lina Lopez Ricaurte (Station Biologique de Doñana – CSIC, Espagne) présentera en salle Jean-Paul Taris un séminaire en anglais intitulé « Are migrating Lesser kestrels time or energy minimizers? Using GPS and environmental data to unfold migratory strategies » ; l’accès est libre et sans inscription.
Migratory birds have an enormous plasticity to carry out seasonal migratory journeys. Much of this flexibility has evolved as biological adaptations of mobile organisms to the unforeseen environmental conditions over which they migrate. Optimal migration theory is a useful theoretical framework to predict the migratory strategy birds should use.
According to the theory, decision-making processes are driven primarily by energy budget and time optimisation criteria. Whilst individuals that reduce the migration duration are time-minimizers, individuals that minimize energy expenditure are energy-minimizers.
We examined the migration GPS tracks of 48 lesser kestrels (Falco naumanni) breeding in Spain and Italy at different temporal scales. Kestrels can use thermals to soar during the day but can also migrate with flapping flight, thus, they can extend their daily migratory flight through the night and, to some degree, migrate under adverse weather conditions. We hypothesize that among lesser kestrel there is a strategic trade-off in migratory behaviour, which varies from energy-minimizers to time-minimizers and that is dependant upon environmental conditions.
The Lesser Kestrel , as other raptors, has a reversed sexual size-dimorphism. Assuming competition for breeding resources, we hypothesize that during spring migration males would arrive earlier to the breeding sites (behave as time-minimizers) and females would spend more time at stopover sites (bahave as energy-minimizers).
Our study highlights the importance of an optimal theory approach to elucidate migration strategies. Decision-making about how, when and where to move, play an important role in ensuring that individuals get safely from the starting to the end of the migration. Poor decision making could be the root cause of many migratory failures, having deleterious impacts on individual fitness and ultimately influence population dynamics.
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