Spatial ecology and migration of calonectris shear watersnew insights from spanish populations revealed by biologging

Resumen

The revolution in biologging and satellite telemetry technologies in the last two decades has led to a new era in seabird research. This thesis brings new insights into the spatial ecology and migration of the Cory’s and the Scopoli’s shearwaters (Calonectris borealis and C. diomedea, respectively), offering a comprehensive overview of these topics for the Spanish populations of these model species. In particular, the thesis provides new knowledge about the movement patterns, at-sea behaviour and the marine environment they inhabit year-round, through the use of GPS loggers and light-level geolocators. Along the chapters of the thesis, I illustrate the potential and applications of biologging in seabird research and conservation. To do so, I address different questions aimed to evaluate the role of environmental features, fisheries, and breeding constraints in the foraging strategies and at-sea behaviour of tracked birds. We found that females of Scopoli’s shearwater generally attended fisheries less than males, and both sexes associated less to fishing boats during unfavourable conditions. Sea surface temperature likely plays a role in individual decision-making: we found that birds may use this environmental feature to decide foraging trip destination. Moreover, we found variability in foraging trips at inter-annual scale, likely due to environmental fluctuations, but also at intra-annual scale, likely due to the different breeding constraints over the breeding period. We explored seabird behaviour from novel ways, deriving simple metrics that may enhance the use of seabirds as sentinel species. Last, we unveiled the role of individual differences in trophic ecology, and discussed the implications of such differences in the use of seabirds to monitor long term fluctuations in a complex upwelling ecosystem. This thesis compiles and summarises the previous knowledge of the Spanish populations of Cory’s and Scopoli’s shearwaters, and extends it with novel insights. Moreover, in a transversal way, I discuss the role of seabirds as indicator species, particularly considering the use of biologging to enhance their suitability as ocean sentinels within the framework of ecosystem-based management.