Colonial breeding is widespread among animals. Some, such as eusocial insects, may use agonistic behavior to partition available foraging habitat into mutually exclusive territories; others, such as breeding seabirds, do not. We found that northern gannets, satellite-tracked from twelve neighboring colonies, nonetheless forage in largely mutually exclusive areas and that these colony-specific home ranges are determined by densitydependent competition. This segregation may be enhanced by individual-level public information transfer, leading to cultural evolution and divergence among colonies.Main Text: Colonial animals are constrained by their colony locations, which are ultimately limited by resource availability (1). However, within species, potential colony home ranges often overlap, implying competition among colonies may also be limiting (2). In eusocial central-place foragers the spatial effects of direct competition among colonies are well understood (2). In contrast, the spatial influences of indirect competition and information transfer on non-territorial species (e.g. seals, swallows and seabirds), where levels of relatedness are much lower, remain conjectural. For example, the hinterland model (3) predicts that breeding seabirds segregate along colonial lines, because of inequalities in travel costs from each colony. Predicted home ranges therefore comprise Voronoi polygons (Fig. 1A), as seen in some territorial animals (2). Food availability is assumed to be proportional to polygon area, limiting colony size. An alternative model proposes that density-dependent competition among colony members is limiting (4). As colonies grow, local prey depletion or disturbance requires birds to travel further to provision their young. However, this model ('Ashmole's halo') does not consider interactions among colonies and tacitly assumes that adjacent colonies' home ranges overlap (5).Indirect evidence exists to support both models (3,6,7) and recent tracking studies suggest that seabirds and pinnipeds segregate along colonial lines (8-12). However, these studies proved inconclusive on the causes and ubiquity of segregation, largely because few colonies were sampled or tracking resolution was low. Here we use high resolution satellite-tracks of the foraging movements of 184 chick-rearing northern gannets Morus bassanus (hereafter gannets) from 12 of the 26 colonies fringing the British Isles (median 17 birds/colony), representing ~80% of the area's breeding population (Fig. 1A, Table S1), to test whether among-colony segregation occurs in a model colonial non-territorial central-place forager. We then use population-and individual-level models to explore potential mechanisms underlying spatial segregation.Gannets are wide-ranging (max. foraging range ~700 km) pelagic seabirds that forage in patches of enhanced production, primarily on shoaling, mesotrophic fish and to a lesser extent fisheries discards (13)(14)(15). In almost all cases we tracked birds from adjacent colonies simultaneously (16). Individua...

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Which factors shape animals' migration movements across large geographical scales, how different migratory strategies emerge between populations, and how these may affect population dynamics are central questions in the field of animal migration [1] that only large-scale studies of migration patterns across a species' range can answer [2]. To address these questions, we track the migration of 270 Atlantic puffins Fratercula arctica, a red-listed, declining seabird, across their entire breeding range. We investigate the role of demographic, geographical, and environmental variables in driving spatial and behavioral differences on an ocean-basin scale by measuring puffins' among-colony differences in migratory routes and day-to-day behavior (estimated with individual daily activity budgets and energy expenditure). We show that competition and local winter resource availability are important drivers of migratory movements, with birds from larger colonies or with poorer local winter conditions migrating further and visiting less-productive waters; this in turn led to differences in flight activity and energy expenditure. Other behavioral differences emerge with latitude, with foraging effort and energy expenditure increasing when birds winter further north in colder waters. Importantly, these ocean-wide migration patterns can ultimately be linked with breeding performance: colony productivity is negatively associated with wintering latitude, population size, and migration distance, which demonstrates the cost of competition and migration on future breeding and the link between non-breeding and breeding periods. Our results help us to understand the drivers of animal migration and have important implications for population dynamics and the conservation of migratory species.

1. Distribution maps of cetaceans and seabirds at basin and monthly scales are needed for conservation and marine management. These are usually created from standardized and systematic aerial and vessel surveys, with recorded animal densities interpolated across study areas. However, distribution maps at basin and monthly scales have previously not been possible because individual surveys have restricted spatial and temporal coverage.2. This study develops an alternative approach consisting of: (a) collating diverse survey data to maximize spatial and temporal coverage, (b) using detection functions to estimate variation in the surface area covered (km 2 ) among these surveys, 254 | Journal of Applied Ecology WAGGITT eT Al. Synthesis and applications.This study provides the largest ever collation and standardization of diverse survey data for cetaceans and seabirds, and the most comprehensive distribution maps of these taxa in the North-East Atlantic. These distribution maps have numerous applications including the identification of important areas needing protection, and the quantification of overlap between vulnerable species and anthropogenic activities. This study demonstrates how the analysis of existing and diverse survey data can meet conservation and marine management needs.