Spread of Antarctic vegetation by the kelp gull: comparison of two maritime Antarctic regions

Abstract

In the present paper, we compare how the kelp gull, Larus dominicanus, utilizes various nest building materials, particularly vascular plants, bryophytes, lichens and other components, in the Fildes Peninsula area (King George Island) and on the Argentine Islands area. In both areas, nest material primarily consisted of the Antarctic hairgrass (Deschampsia antarctica), bryophytes, lichens, feathers, limpets, and algae. Our study reveals area-specific differences in the utilization of plants for nest building related to local conditions during the nesting season. In the Fildes area, vegetation emerges from under the winter snow cover earlier in the spring, giving the gulls greater choice locally, meaning that the gulls need not resort to long distance material transfer. Here, mosses and lichens dominate in the nest material, likely collected from the nearby vegetation formations. The Antarctic hairgrass in these conditions is mostly found in nests located directly within hairgrass formations. However, on the more southern Argentine Islands, kelp gulls routinely use D. antarctica and some mosses, transferring them from coastal hill tops where snow generally disappears earlier. Here, the gulls appear to be selective still, as they rarely use some mosses, such as Polytrichum strictum, that are abundant near the nesting locations. In the Argentine Islands area, we documented long-range transfer of the Antarctic hairgrass and some other vegetation materials from places of abundance to bare rocks of low islands lacking developed vegetation. This demonstrates the potential of the gulls to serve as dispersal and gene pool exchange agents for the local terrestrial biota in the maritime Antarctic, especially between highly isolated populations from small islands and ice-free areas.