Intraspecific competition as potential drivers of dispersive migration in a pelagic seabird, the Atlantic puffin Fratercula arctica. Puffins are small North Atlantic seabirds that exhibit dispersive migration (Guilford et al. 2011; Jessopp et al. 2013), although this varies between colonies (Harris et al. 2010). The migration strategies of seabirds, although less well understood than those of terrestrial species, seem to show large variation in flexibility between species, making them good models to study flexibility in migratory strategies (Croxall et al. 2005; Phillips et al. 2005; Shaffer et al. 2006; Gonzales-Solis et al. 2007; Guilford et al. 2009). Here, we track the migration of over 100 complete migrations of puffins using miniature geolocators over 8 years. First, we investigate the role of random dispersion (or semirandom, as some directions of migration, for example, toward land, are unviable) after MedChemExpress EGF816 breeding by tracking the same individuals for up to 6 years to measure route fidelity. Second, we examine potential sex-driven segregation by comparing the migration patterns of males and females. Third, to test whether dispersive migration results from intraspecific competition (or other differences in individual quality), we investigate potential relationships between activity budgets, energy expenditure, laying date, and breeding success between different routes. Daily fpsyg.2015.01413 activity budgets and energy expenditure are estimated using saltwater immersion data simultaneously recorded by the devices throughout the winter.by the British Trust for Ornithology Unconventional Methods Technical Panel (permit C/5311), Natural Resources Wales, Skomer Island Advisory Committee, and the University of Oxford. To avoid disturbance, handling was kept to a minimum, and indirect measures of variables such as laying date were preferred, where possible. Survival and breeding success of manipulated birds were monitored and compared with control birds.Logger deploymentAtlantic puffins are small auks (ca. 370 g) breeding in dense colonies across the North Atlantic in summer and spending the rest of the year at sea. A long-lived monogamous species, they have a single egg clutch, usually in the same burrow (Harris and Wanless 2011). This study was carried out in Skomer Island, Wales, UK (51?4N; 5?9W), where over 9000 pairs breed each year (Perrins et al. 2008?014). Between 2007 and 2014, 54 adult puffins were caught at their burrow nests on a small section of the colony using leg hooks and purse nets. Birds were ringed using a BTO metal ring and a geolocator was attached to a plastic ring (models Mk13, Mk14, Mk18– British Antarctic Survey, or Mk4083–Biotrack; see Guilford et al. rstb.2013.0181 2011 for detailed methods). All birds were color ringed to allow visual identification. Handling took less than 10 min, and birds were released next to, or returned to, their burrow. Total deployment purchase E7449 weight was always <0.8 of total body weight. Birds were recaptured in subsequent years to replace their geolocator. In total, 124 geolocators were deployed, and 105 complete (plus 6 partial) migration routes were collected from 39 individuals, including tracks from multiple (2?) years from 30 birds (Supplementary Table S1). Thirty out of 111 tracks belonged to pair members.Route similarityWe only included data from the nonbreeding season (August arch), called "migration period" hereafter. Light data were decompressed and processed using the BASTrack software suite (British Antar.Intraspecific competition as potential drivers of dispersive migration in a pelagic seabird, the Atlantic puffin Fratercula arctica. Puffins are small North Atlantic seabirds that exhibit dispersive migration (Guilford et al. 2011; Jessopp et al. 2013), although this varies between colonies (Harris et al. 2010). The migration strategies of seabirds, although less well understood than those of terrestrial species, seem to show large variation in flexibility between species, making them good models to study flexibility in migratory strategies (Croxall et al. 2005; Phillips et al. 2005; Shaffer et al. 2006; Gonzales-Solis et al. 2007; Guilford et al. 2009). Here, we track the migration of over 100 complete migrations of puffins using miniature geolocators over 8 years. First, we investigate the role of random dispersion (or semirandom, as some directions of migration, for example, toward land, are unviable) after breeding by tracking the same individuals for up to 6 years to measure route fidelity. Second, we examine potential sex-driven segregation by comparing the migration patterns of males and females. Third, to test whether dispersive migration results from intraspecific competition (or other differences in individual quality), we investigate potential relationships between activity budgets, energy expenditure, laying date, and breeding success between different routes. Daily fpsyg.2015.01413 activity budgets and energy expenditure are estimated using saltwater immersion data simultaneously recorded by the devices throughout the winter.by the British Trust for Ornithology Unconventional Methods Technical Panel (permit C/5311), Natural Resources Wales, Skomer Island Advisory Committee, and the University of Oxford. To avoid disturbance, handling was kept to a minimum, and indirect measures of variables such as laying date were preferred, where possible. Survival and breeding success of manipulated birds were monitored and compared with control birds.Logger deploymentAtlantic puffins are small auks (ca. 370 g) breeding in dense colonies across the North Atlantic in summer and spending the rest of the year at sea. A long-lived monogamous species, they have a single egg clutch, usually in the same burrow (Harris and Wanless 2011). This study was carried out in Skomer Island, Wales, UK (51?4N; 5?9W), where over 9000 pairs breed each year (Perrins et al. 2008?014). Between 2007 and 2014, 54 adult puffins were caught at their burrow nests on a small section of the colony using leg hooks and purse nets. Birds were ringed using a BTO metal ring and a geolocator was attached to a plastic ring (models Mk13, Mk14, Mk18– British Antarctic Survey, or Mk4083–Biotrack; see Guilford et al. rstb.2013.0181 2011 for detailed methods). All birds were color ringed to allow visual identification. Handling took less than 10 min, and birds were released next to, or returned to, their burrow. Total deployment weight was always <0.8 of total body weight. Birds were recaptured in subsequent years to replace their geolocator. In total, 124 geolocators were deployed, and 105 complete (plus 6 partial) migration routes were collected from 39 individuals, including tracks from multiple (2?) years from 30 birds (Supplementary Table S1). Thirty out of 111 tracks belonged to pair members.Route similarityWe only included data from the nonbreeding season (August arch), called "migration period" hereafter. Light data were decompressed and processed using the BASTrack software suite (British Antar.