Arctic tern migration : from individual variation to common flyways of trans-equatorial seabirds

Arctic terns are iconic seabirds, famous for annual migrations between the Arctic and Antarctic. Recent assessment suggests they are one of the most vulnerable seabirds to climate change. Its wide geographical range hinders the detection of hazards faced by the species during its annual bi-hemispheric movements. Although Arctic terns breed in the Pacific, Atlantic and Arctic coasts of North America, few tracking studies have been conducted on North American Arctic terns, and none in Canada, which represents a significant proportion of their circumpolar breeding range. Using light-level geolocators, I tracked 53 Arctic terns from 5 breeding colonies across a wide latitudinal and longitudinal range within North America. In Chapter 2, I compared the routes taken by terns in our study to those previously tracked from Greenland, The Netherlands, Sweden, Norway, Maine (USA), and Alaska (USA). Most Arctic terns tracked globally used one of three southbound migration routes: 1) Atlantic West Africa; 2) Atlantic Brazil; 3) Pacific coastal, and one of two northbound migration routes: 1) Mid-ocean Atlantic; 2) Mid-ocean Pacific. These migration corridors were also used by many other trans-equatorial seabirds, suggesting that Arctic tern routes are important for multiple seabird species. However, my results show little overlap between these routes and internationally-recognized Waterbird Flyways. This research suggests that Arctic tern migration habitat, where they spend 4-6 months per year, is currently mostly unprotected and that identification of seabird-specific flyways would benefit seabird conservation. These novel findings could inform international discussions for the protection of primary migratory corridors of vulnerable seabirds. In Chapter 3, I analyzed the factors that explained individual migratory variation among Arctic terns by using wet-activity data simultaneously recorded by the geolocators. Southbound migration was longer in duration than northbound, and colony latitude best explained this seasonal difference and total duration of each migration. Daily individual variation was also greater during the northbound migration, suggesting breeding terns potentially travel faster than non-breeding terns. Two individuals exhibited previously-unknown migration strategies of staying on-land or resting mid-flight. While migration routes are shared, migration duration is variable across colonies and individuals, suggesting that timing should be considered in flyways conservation.Science, Faculty ofOceans and Fisheries, Institute for theGraduat