Ressource pédagogique : Towards a tracking of past bird seasonal migrations through geological times: what could isotopes tell us? / Anaïs Duhamel

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Towards a tracking of past bird seasonal migrations through geological times: what could isotopes tell us? / Anaïs Duhamel, in colloque "1st Virtual Conference for Women Archaeologists and Paleontologists. Nouveaux apports à l’étude des populations et environnements passés" organisé par le laboratoire Travaux et Recherches Archéologiques sur les Cultures, les Espaces et les Sociétés (TRACES) de l’Université Toulouse Jean Jaurès et le laboratoire Paléontologie Évolution Paléoécosystèmes (PALEVOPRIM) de l'Université de Poitiers, sous la responsabilité scientifique de Julie Bachellerie, Ana Belén Galán López (Traces), Émilie Berlioz et Margot Louail (Palevoprim). Université Toulouse Jean Jaurès, 8-9 mars 2021. Session 2 : Occupation of territories and population mobility. [Conférence enregistrée en distanciel]. Bird annual migrations are today a major phenomenon shaping communities across continents, in a cyclical way highly dependent on climatic seasonality gradients. Long-distance avian migrations, in particular, have long been considered relatively recent, essentially triggered and shaped by Pleistocene glacial-interglacial cycles. It is now accepted that these modern migrations originated within different lineages in much older times, probably the late Paleogene. Nevertheless, concrete evidence for these ancient migrations through geological times are very scarce. Since long-distance migrants fly across and stop in areas with contrasted climatic conditions and bedrock mineralogies throughout a year, an approach with isotopes such as stable oxygen and radiogenic strontium seems a promising avenue. I will present here how isotopic signals can be recorded in bird bones through a model, considering several constraints. Based on existing GPS data, migration trackways of 10 species of extant long-distance migrants were mapped and correlated with the oxygen and strontium isotope compositions at each stopover locations frequented by the bird. Model outputs predict that migrating birds can be recognized from sedentary birds. This model is to be validated by analyzing bones of extant birds whose migratory behaviour is known, this work being in progress this year for the oxygen isotope composition of bone. If successful, then the methodology will be applied to fossil bird bones, taking into account past climate context. Results could yield the most concrete evidence of past migrations, and greatly help to understand the evolution of this fascinating behaviour, notably its variations in response to past and present-day climate changes.

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• Paléontologie. Paléozoologie (560)

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