Understanding migration of pelagic seabirds with stable isotopes and geolocation
- Autores: Teresa Militao
- Directores de la Tesis: Jacob González-Solís i Bou (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2016
- Idioma: español
- Tribunal Calificador de la Tesis: Lluís Cardona Pascual (presid.), José Augusto Belchior Alves (secret.), Steffen Oppel (voc.)
- Programa de doctorado: Programa Oficial de Doctorado en Biodiversidad
- Materias:
- Enlaces
- Tesis en acceso abierto en: Dipòsit Digital de la UB TDX
- Resumen
Animal migration is an amazing widespread phenomenon that forms an essential component of the animal life history. Animals usually migrate to take advantages of changes in resource availability in space and time or to find suitable habitats for different life-history stages, which ultimately may improve their fitness. Unfortunately, migratory species are currently experiencing substantial population declines because of the several threats they are exposed to. These largely depend on their migratory patterns, and therefore its study is crucial for the effective conservation of migratory species. Despite our wealth of knowledge on avian migration, the study of migratory ecology of pelagic seabirds is still very challenging, especially in small species. Until recently, most studies on seabird migration focused on species of the Southern Ocean, while our knowledge on Mediterranean, tropical and subtropical Atlantic species is scarcer.
In this thesis, we aim to fill in this gap of knowledge for a number of pelagic seabirds of the Mediterranean and the Atlantic, by studying the migratory patterns of 7 shearwaters, 4 petrels and 1 gull species. More specifically, we (1) increase our knowledge on different methodologies for seabird identification as a preliminary step to study their migratory movements; (2) evaluate the utility of stable isotopes analysis (SIA) to infer the non-breeding areas of pelagic seabirds, and; (3) reveal the migratory patterns and non-breeding areas of the study species using geolocation or a combination of SIA and geolocation data.
Our findings pointed out the importance of integrating different methodologies to distinguish individuals of closely related or recently diverged species and thus overcome their identification difficulty. Furthermore, we demonstrated the utility of SIA as powerful approach to discriminate species that explore isotopically distinct areas. We verified a generally high efficiency of SIA on feathers as a geographic marker to infer the previous non-breeding area of pelagic seabirds. However, SIA efficiency varied at inter-specific level depending on the degree of isotopic differentiation among their non-breeding areas.
Based on geolocation and isotopic data, we found a huge variability in migratory patterns among species, population and individuals. At inter-population level, we described for the first time a leap-frog migration pattern in an oceanic seabird, while at intra-population level we revealed the existence of partial migration and other complex migratory patterns.
Additionally, we integrated our results and information from literature to review the main extrinsic and intrinsic drivers of migratory patterns of small and medium size seabirds and how they may differ from the ones affecting the migration of terrestrial birds. In opposite to the characteristics of terrestrial habitats, the almost lack of major barriers to migration, the low productivity of tropical waters and the biological adaptations of seabirds to the oceanic habitats seem to contribute to the long-distance migrations and huge variability in migratory patterns of small and medium sized pelagic seabirds. However, this variability is still smaller than the one observed in terrestrial species probably because of the absence of major barriers and the milder climatic seasonality of the oceans.
Overall, this thesis gives an important contribution to a wider understanding of the complex migratory ecology of pelagic seabirds.
