Fine-scale spatial segregation in a pelagic seabird driven by differential use of tidewater glacier fronts

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.

Forty years of warming: Environmental change in marine coastal habitats on Svalbard between 1981 and 2022

“…For the coastal waters, glacier retreat means also intense sediment outflow and freshwater discharge. The change in tidal glacier fronts impacts the local food web, especially seabirds that use this specific habitat (Stempniewicz et al 2017;Bertrand et al 2021;Hop et al 2023). Shoreline areas free from the glacier are inhabited by minute mobile fauna like Oligochaeta or Gammarus assemblages (Węsławski et al 1993a, b).…”

Aggregations of foraging black guillemots (Cepphus grylle) at a sea-ice edge in front of a tidewater glacier

“…The black guillemots were not evenly distributed along the ice edge but were aggregated near the well-defined outflow that was likely meltwater from the glacier. Plumes and upwelling in front of tidewater glacier fronts are well known to attract large numbers of foraging seabirds (Hartley & Fisher 1936;Stott 1936;Mehlum 1984;Węsławski & Legeżyńska 1998;Węsławski et al 2000;Lydersen et al 2014;Bertrand et al 2021). Themisto libellula and Thysanoessa sp., which we observed nearer to Kronebreen, have been reported as abundant near glaciers in Kongsfjorden (Węsławski et al 2000), and their presence near the surface led Węsławski et al (2000) to suggest that the zooplankton was entrapped by the estuarine circulation, and that the freshwater possibly impairs the zooplankton, making them relatively easy prey (Lydersen et al 2014).…”

“…Seabirds are known to aggregate in the Arctic marginal ice zone because of the good feeding conditions (Bradstreet 1979(Bradstreet , 1980Lønne & Gabrielsen 1992;Divoky et al 2016), with similar patterns in the Antarctic (e.g., Tarroux et al 2020). Arctic seabirds, particularly surface feeders, also aggregate near tidewater glaciers (also known as marine-terminating glaciers) in the melting season (McLaren & Renaud 1982;Lydersen et al 2014;Stempniewicz et al 2017;Nishizawa et al 2020;Bertrand et al 2021). Freshwater run-off from tidewater glaciers leads to upwelling and the entrapment of zooplankton, which results in predictable aggregations of prey (Węsławski et al 2000;Lydersen et al 2014;Urbanski et al 2017).…”

Nutrient fluxes from an Arctic seabird colony to the adjacent coastal marine ecosystem

“…with Kittiwakes tending to be more attracted to marine-terminating glacier fronts than Guillemots (Urbanski et al 2017;Nishizawa et al 2020). Both species will forage relatively nearby their colonies during the breeding season, commonly within a radius of 20 km from the colony and rarely leaving on foraging trips more than 50 km away from the colony (Mehlum et al 2001;Falk et al 2002;Bertrand et al 2021). The diet of Kittiwakes in Svalbard is dominated by fish, with polar cod (Boreogadus saida) being an important food item (Lønne and Gabrielsen 1992), along with crustaceans and other marine invertebrates (Vihtakari et al 2018).…”