Abstract
In colonially breeding marine predators, individual movements and colonial segregation are influenced by seascape characteristics. Tidewater glacier fronts are important features of the Arctic seascape and are often described as foraging hotspots. Albeit their documented importance for wildlife, little is known about their structuring effect on Arctic predator movements and space use. In this study, we tested the hypothesis that tidewater glacier fronts can influence marine bird foraging patterns and drive spatial segregation among adjacent colonies. We analysed movements of black-legged kittiwakes (Rissa tridactyla) in a glacial fjord by tracking breeding individuals from five colonies. Although breeding kittiwakes were observed to travel up to ca. 280 km from the colony, individuals were more likely to use glacier fronts located closer to their colony and rarely used glacier fronts located farther away than 18 km. Such variation in the use of glacier fronts created fine-scale spatial segregation among the four closest (ca. 7 km distance on average) kittiwake colonies. Overall, our results support the hypothesis that spatially predictable foraging patches like glacier fronts can have strong structuring effects on predator movements and can modulate the magnitude of intercolonial spatial segregation in central-place foragers.
Highlights
In colonially breeding marine predators, individual movements and colonial segregation are influenced by seascape characteristics
The global analysis of similarities (ANOSIM) indicated that the dissimilarity in space use was greater among colonies than within colonies
While showing no sign of heterogeneous dispersion among groups (F4,33 = 0.93, p = 0.457), the ANOSIM analysis conducted on each pair of colonies suggested that all colonies showed significant spatial segregation, except the Blomstrand (BLM)—Observasjonsholmen (OBS) dyad (Table 2)
Summary
In colonially breeding marine predators, individual movements and colonial segregation are influenced by seascape characteristics. Driven by the meltwater glacier discharge at the fronts, zooplankton are entrained and transported by the buoyant subglacial plumes at the ice-sea interface, making prey readily available at the surface for p redators[22,27–29] Their relative profitability can vary over time[30–34], glacier fronts may represent spatially predictable foraging habitats for breeding colonial seabirds[30,31,33] due to their geographically restricted and relatively fixed location. Despite their documented importance as foraging hotspots, little is known about their structuring effect on predator distribution patterns and movements. Focusing on Arctic breeding black-legged kittiwakes (Rissa tridactyla), our study aims at testing the hypothesis that tidewater glacier fronts represent high value patches that modulate seabird foraging patterns and generate fine-scale spatial segregation among neighbouring colonies. While controlling for differences in colony size and distance separating colonies[11,13], we further predicted that differential use of glacier fronts promotes a fine-scale spatial segregation (i.e., less overlap than what would be expected from distance alone) among neighbouring colonies
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