The causes and consequences of pelagic seabird foraging routines
Pelagic seabirds are apex predators harvesting patchily distributed, dynamic marine resources on spectacular spatial scales. How they do so is key to understanding their natural at-sea movements and distributions, their vulnerability to the impacts of ocean industrialisation, and their response to environmental change. Indeed, they have sometimes been described as the sentinels of ocean health. Because they often forage far from land, studying the foraging movements of pelagic seabirds systematically has only recently become possible with the advent of miniaturised biotelemetry systems. Where foraging tactics previously had to be inferred from arrival and departure characteristics at the colonies, we can now measure the patterns of movement and foraging activity much more directly using on-board GPS and dive or immersion loggers. At OxNav we are particularly interested in the underlying behavioural mechanisms that drive the patterns of marine resource exploitation in pelagic seabirds in our long-term studied model species, the Manx shearwater which breeds on islands primarily off the UK. The student selected for this project would have considerable autonomy to develop their own ideas and approaches, but as a starting point we propose to combine aspects of competition theory and optimal foraging theory (specifically resource geometry theory) to structure investigation of shearwater foraging routines, and how these might lead to observed apparent segregation of at-sea distributions from neighbouring colonies.
Shearwaters travel 100s, even 1000s, of kilometres on foraging trips away from their breeding colonies, sometimes alternating between chick provisioning and self-feeding: the so-called “dual foraging strategy”. The routes they take on these trips will be measured from our long-term archive of annual GPS tracks, and from targetted new tracking during the project, with foraging activity at each visited location measured from co-deployed immersion loggers. The aim will be to characterise shearwater foraging routines and address one or more specific hypotheses about whether they: 1) are optimal travel solutions for maximising chick provisioning rates or compromises between self- and chick- provisioning; 2) indicate competitive segregation between neighbouring colonies; 3) are responsive to changing environmental conditions, both short and long term; 4) reveal the role of individual experience, memory and reward uncertainty in foraging route decisions. Finally, understanding the drivers and patterns of shearwater foraging movements is now a timely conservation priority because of the imminent rapid expansion of off-shore wind development in the Celtic and Irish seas, and this project will be pursued in collaboration with colleagues at the RSPB in a CASE partnership.
Please contact Tim Guilford on firstname.lastname@example.org and Mark Bolton on email@example.com if you are interested in this project