What's for dinner? Oceanographic drivers of Manx shearwater chick provisioning and growth

Oceanographic features (e.g. fronts, gyres and eddies) are known to aggregate pelagic forage fish and thereby shape the space use of marine predators1,2. These features are dynamic and changes in their characteristics (e.g. strength, persistence, position) has consequences for prey availability, foraging effort

and breeding success3 . The NERC SHEAR project is currently quantifying how the association and interaction between physical oceanographic features and prey availability impacts Manx shearwater foraging energetics, a pelagic diving seabird known to forage in close association with oceanographic features. However, there is a significant knowledge gap surrounding the diet composition of Manx

shearwaters4 which is partly because previous methods for studying the diet of these birds have been invasive. DNA metabarcoding and less invasive sampling techniques are now transforming diet studies of such species5 . Furthermore, less is known about how variation in oceanographic features drive the

availability of specific prey species (i.e., squid and small Clupeid fish) within key foraging areas. This is important as prey species differ significantly in calorific value, and diets consisting predominantly of 'junk food' have had significant consequences for the growth and survival of seabird offspring6

. This multidisciplinary project will identify the fine-scale links between characteristics of oceanographic features and species of forage fish as well as quantify the key drivers of shearwater chick growth using a combination of biologging, eDNA analysis, morphometric measurements, and physical oceanography.

Specifically, this project has three core questions: 1. Does the characteristics of physical oceanographic features determine shearwater foraging depth and effort? 2. Is meal size and diet determined by the characteristics of physical oceanographic features targeted during foraging trips? 3. Is chick growth explained by Qs 1 & 2?