Seabird assemblages observed during the BROKE-West survey of the Antarctic coastline (30-80 E), January-March 2006
Observations of the numbers and behaviours of all seabirds present within a 300m forward quadrant of the ship were recorded continuously while the vessel was underway during daylight hours. Ship-followers were excluded from all analyses following BIOMASS Working Party on Bird Ecology (1982) as these...
| Summary: | Observations of the numbers and behaviours of all seabirds present within a 300m forward quadrant of the ship were recorded continuously while the vessel was underway during daylight hours. Ship-followers were excluded from all analyses following BIOMASS Working Party on Bird Ecology (1982) as these individuals bias abundance estimates and reduce statistical correlations between seabirds and the physical environment. Ship-followers typically associate with the vessel for extended periods, either following the vessel at the stern or circling the vessel, or both. Data for prions (Pachyptila spp.) and dark shearwaters (Puffinus griseus and P. tenuirostris) have been pooled as with previous analyses, as these are difficult to separate at sea. Seabird surveys in January - March 2006 of a poorly known area of the Southern Ocean adjacent to the East Antarctic coast identified six seabird communities, several of which were comparable to seabird communities identified both in adjacent sectors of the Antarctic, and elsewhere in the Southern Ocean. These results support previous proposals that the Southern Ocean seabird community is characterised by an ice-associated assemblage and an open-water assemblage, with the species composition of the assemblages reflecting local (Antarctic-resident) breeding species, and the migratory routes and feeding areas of distant-breeding taxa, respectively. Physical environmental covariates such as sea-ice cover, distance to continental shelf and time of year influenced the distribution and abundance of seabirds observed, but the roles of these factors in the observed spatial and temporal patterns in seabird assemblages was confounded by the duration of the survey. Occurrence of a number of seabird taxa exhibited significant correlations with krill densities at one or two spatial scales, but only three taxa (Arctic tern, snow petrel and dark shearwaters, i.e. sooty and short-tailed shearwaters) showed significant correlations at a range of spatial scales. Dark shearwater abundances showed correlations with krill densities across the range of spatial scales examined. This work was conducted on the BROKE-West voyage of the Aurora Australis. |
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