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

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 majorphenomenon shaping communities across continents, in a cyclical way highlydependent on climatic seasonality gradients. Long-distance avian migrations, inparticular, have long been considered relatively recent, essentially triggeredand shaped by Pleistocene glacial-interglacial cycles. It is now accepted thatthese modern migrations originated within different lineages in much oldertimes, probably the late Paleogene. Nevertheless, concrete evidence for theseancient migrations through geological times are very scarce. Sincelong-distance migrants fly across and stop in areas with contrasted climatic conditionsand bedrock mineralogies throughout a year, an approach with isotopes such asstable oxygen and radiogenic strontium seems a promising avenue. I will presenthere how isotopic signals can be recorded in bird bones through a model,considering several constraints. Based on existing GPS data, migrationtrackways of 10 species of extant long-distance migrants were mapped andcorrelated with the oxygen and strontium isotope compositions at each stopoverlocations frequented by the bird. Model outputs predict that migrating birdscan be recognized from sedentary birds. This model is to be validated byanalyzing bones of extant birds whose migratory behaviour is known, this workbeing 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 accountpast climate context. Results could yield the most concrete evidence of pastmigrations, and greatly help to understand the evolution of this fascinatingbehaviour, notably its variations in response to past and present-day climatechanges.