ndividual variation in space use across spatial scales in shearwaters (Puffinus spp.)

Within-species variation in behaviour is increasingly studied in wild animal populations for its evolutionary implications and a more detailed understanding of how individual animals interact with their environment. Appreciation that such individual differences are consistent across time (Dammhahn and Almeling, 2012) and can lead to predictions of how animals respond to environmental change (van Overveld and Matthysen, 2013; Spiegel et al., 2015), conservation policies (Merrick and Koprowski, 2017) and scientific manipulation (Biro and Dingemanse, 2009) has led to increased interest in how they emerge and function. In addition, understanding how individual differences emerge invites reflection both as to how mechanisms underlying control of behaviour operate, and how individual-level processes contribute to population-level outcomes, or how behaviour translates into ecology. Having a measure of the degree of individual variation in a population is also important in understanding that population's ecology in greater depth (Bolnick et al., 2003, 2011).Animal space use is of great ecological significance, with consequences for foraging, territory holding, interaction with conspecifics and disease dynamics. Analysis of spatial behaviour is a promising avenue for investigating individual behavioural differences as it is relatively straightforward to interpret; it is also practically feasible as an animal's movement is readily quantifiable and this is becoming easier as biologging technology becomes lighter and cheaper. The Oxford Navigation Group has been studying Manx shearwaters (Puffinus puffinus) and Balearic shearwaters (Puffinus mauretanicus) over many years with GPS- and GLS-logging equipment and consequently multiple large datasets pertaining to different spatial behaviours already exist. These offer a valuable resource for investigating the existence of individual variation, while the UK field sites also permit experimental study of free-ranging Manx shearwaters that may allow precise questions to be asked about individual differences.Both species are central place foragers and migrate annually; they cover large distances in search of prey during both breeding and wintering seasons and are constrained during the breeding season to make recurrent trips to and from the nest, while repeatedly finding their way along the migratory route. With long lifespans and the potential for learning details about the environment, such as the locations of productive foraging areas or efficient migration routes, it is potentially likely that these birds show individual variation in space use; understanding the causes of such variation may go some way to revealing how flexible these behaviours are and their consequences for population dynamics. Indeed, as they occupy a high trophic level these seabirds may be particularly vulnerable to environmental change and anthropogenic disturbance (Grémillet and Boulinier, 2009). Mortality through fishing bycatch and other threats have made the Balearic shearwater the most endangered European seabird, with its population predicted to go extinct in 40-60 years (Genovart et al., 2016). Since its interaction with fisheries is a serious source of its decline (Genovart et al., 2016), understanding how different individuals habitually use different foraging areas might be an important tool in protecting this species, and for informing practices for conserving others.Consistency of individual space use across multiple scales, which represent different elements of life history, would be informative of both the mechanisms and functions of individual variation for the species' ecology and vulnerabilities.