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Abstract

The presence of 31 species of birds was observed at sea sout of 50°S, out of this number 26 species were present also south of 60°S. The most numerous aggregations of birds were recorded in the regions of: Elephant Island, the South Orkneys and NE part of Bransfield Strait. The average number of birds during 10-minute observation was 74.5. In the areas under observations Daption capense predominated quantitatively. The following species were subdominant: Pygoscelidae, Oceanites oceanicus, Diomedea melanophris, Fulmarus glacialoides and Macronectes giganieus. In the total number of the birds observed krill-eaters contributed in 80.1% plankton-eaters — 7.8%, squid-eaters — 6.2% omnivores — 5.9% and fish-eaters — 0.1%. In comparison with the autumnal observations more than twice as many birds at sea were observed in the same area.
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Abstract

The aim of the study was to compare cyanobacterial and algal assemblages occurring in ornithocoprophilous habitats formed under the influence of two seabird colonies (mixed colony of piscivorous Uria lomvia and Rissa tridactyla and planktivorous Alle alle) nesting on the southwest side of Hornsund (Spitsbergen). Various influences of the bird colonies (e.g. surface trophy, treading) lead to the formation of ornithogenic habitats with quantitatively and qualitatively diverse cyanobacterial and algal assemblages. Only 6 species common to both habitats were identified, but due to their different proportions the similarity ended there. Cyanobacterial and algal assemblages of both ornithogenic habitats also react rather differently to the intensity of the bird colonies' influence. The assemblages located directly beneath piscivorous bird nests were characterized by a larger number of species, which decreased the farther from the colony it was. Cyanobacterial and algal assemblages located directly next to planktivorous bird nests were species poor, but species richness increased at locations farther from their direct influence. The obtained results confirmed that bird colonies characterized by different diet and behavior influenced the formation of two separate, quantitatively and qualitatively different cyanobacterial and algal assemblages. Species such as Eucapsis sp., Gleocapsopsis sp., Gloeothece sp., Woronichinia sp., Hematococcus sp. were characteristic for algae and cyanobacteria assemblages in the vicinity of piscivorous bird colonies, whereas Aphanocapsa sp., Gloeothece sp., Komvophoron minutum, Pseudanabaena sp., Gloeocystis sp. 2 occurred in the vicinity of planktivorous bird colonies.
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