Long-term tracking of an Arctic-breeding seabird indicates high fidelity for pelagic wintering areas

Background/Question/Methods

Animal populations are composed of heterogenous individuals that repeatedly differ in their respective morphological, physiological or behavioural traits. Such variation in traits can reduce intraspecific competition and result in differences in fitness among individuals, with potentially strong impacts on population dynamics. Intra-population variability in phenotypes may provide the genetic variation needed for a population to adapt to environmental changes. Populations with high repeatability in phenotypes may notably be more vulnerable to changes in resource and environmental conditions. In marine systems, resources are patchy and scattered over large spatial scales so that top predators like seabirds often rely on specific higher quality foraging zones (e.g. shelf edges, upwellings) that are predictable over years. Site fidelity is driven by predictable resource distributions in time and space. However, intrinsic factors related to the individual’s physiology and life-history traits can contribute to consistent foraging behaviour and movement patterns. Using 11 years of continuous geolocation tracking data (fall 2008 to spring 2019), we investigated spatiotemporal repeatability in non-breeding movements in a pelagic seabird population of black-legged kittiwake (Rissa tridactyla) breeding in the High Arctic (Svalbard). Our objective was to assess the relative importance of spatial versus temporal repeatability behind inter-annual movement consistency during winter.

Results/Conclusions

Winter site fidelity was high both within and across individuals and at meso (100-1000 km) and macro scales ( >1000 km), including over deep-water areas far from continental shelves. Spatial consistency in non-breeding movement was higher within than among individuals, suggesting that site fidelity might emerge from individuals’ memory to return to locations with predictable resource availability. Consistency was also stronger in space than in time, suggesting that it was driven by consistent resource pulses that may vary in time more so than in space. Specialization for key wintering areas can indicate vulnerability to environmental perturbations and global changes, with winter survival and carry-over effects arising from winter conditions as potential drivers of population dynamics.