Abstract
The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey but also that of competitors (e.g. southerly species expanding their range into the Arctic). Species can respond to interspecific competition by segregating along different niche axes. Here, we studied spatial, temporal and habitat segregation between two closely related seabird species: common guillemot Uria aalge (a temperate species) and Brünnich’s guillemot Uria lomvia (a true Arctic species), at two sympatric sites in Iceland that differ in their total population sizes and the availability of marine habitats. We deployed GPS and temperature-depth recorders to describe foraging locations and behaviour of incubating and chick-rearing adults. We found similar evidence of spatial segregation at the two sites (i.e. independent of population sizes), although segregation in environmental space was only evident at the site with a strong habitat gradient. Unexpectedly, temporal (and, to a limited extent, vertical) segregation appeared only at the least populated site. Overall, our results show complex relationships between the levels of inferred competition and that of segregation.
Highlights
The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey and that of competitors
The ability of subordinate species to escape competition can depend on the availability of refugia habitats that are avoided by dominants[2,6,12]
One Temperature-Depth Recorders (TDR) logger malfunctioned, and as only tracks with both GPS and TDR data available were used, in total 50 CG and 38 Brünnich’s guillemots (BG) were available for analysis (Table S2)
Summary
The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey and that of competitors (e.g. southerly species expanding their range into the Arctic). Interspecific competition is one such biotic factor, and its potential role in refining species ranges has been highlighted in various taxa[2,3] At their range limits, closely related species often co-occur in areas of sympatry. Spatial segregation can be h orizontal[7,8] or vertical[2,9] It is often structured by habitat heterogeneity, as subordinate species can be displaced from otherwise suitable habitats when their dominant competitor is present[10,11]. In the Arctic, where rates of warming are among the most rapid on Earth[18], the northward shift of red foxes Vulpes vulpes increases competitive pressures on Arctic foxes Alopex lagopus[17] This is true in terrestrial environments, and in marine ecosystems. The Atlantic sector of the Arctic is affected by increased inflow of warm, saline waters from the south into Arctic latitudes[19], leading
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