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Rooks show a growing tendency to winter in cities. The aim of this study was to determine the influence of meteorological factors on the selection of feeding habitats and to discuss the diversity of feeding strategies in urban environments of different sizes and housing densities. The study was carried out in two cities in south-western Poland, Wrocław and Brzeg (populations of 636,000 and 39,000, respectively), in the years 2004–2008. Nineteen research areas differing in housing density were controlled once a week. In multiple regression, the number of rooks feeding in urban environments showed a correlation with air temperature and the thickness of snow cover. The densities of feeding rooks were higher in urban environments than in agrocenoses. They were also higher in Wrocław than in Brzeg, and in built-up areas than in undeveloped ones. Feeding groups were smaller in Brzeg than in Wrocław. They were also smaller in built-up areas in Brzeg than in undeveloped ones. More rooks fed individually in Brzeg than in Wrocław. The diversity in the frequency of individually feeding rooks in built-up and undeveloped environments was specific to each city. Rooks feeding in Brzeg were more active in searching for food than those in Wrocław, and birds feeding on optimum, undeveloped feeding grounds were more active than those in built-up areas . In both cities, rooks were fed by humans, mainly in built-up areas.
The Antarctic region has been considered as a region the least exposed to the pollution. However, increase of human activities at the research stations, transportation and tourism threaten the natural environment of this region. The paper reports the contents of selected trace elements in lichen and moss samples collected in the interior parts of several Antarctic research stations located on King George Island (South Shetlands, maritime Antarctica). Lichens and mosses are particularly sensitive to a athropogenic environmental changes, especially to air pollution. Moss Sanionia uncinata and lichens – Usnea antarctica and Usnea aurantiaco-atra were chosen as bioindicators. The amount of ten trace metals (vanadium, chromium, manganese, copper, zinc, lead, rubidium, strontium, yttrium, and cadmium) and bromine was measured in thalli using the analytical PIXE (Particle Induced X-ray Emission) method. The results obtained for the samples originating from research stations were compared with the data obtained for the samples of same species collected in the area distant from any human activities. For the samples from Antarctic stations the average contents of trace elements (in μg g–1 d.w., mean ± SD) were as follows: S. uncinata – V 27 ± 22, Cr 7 ± 2, Mn 256 ± 95, Cu 11 ± 3, Zn 33 ± 4, Pb 9 ± 6, Br 40 ± 22, Rb 14 ± 11, Sr 69 ± 25; U. antarctica – V 28 ± 31, Cr 3 ± 1, Mn 53 ± 18, Cu 10 ± 4, Zn 30 ± 1, Pb 2 ± 1, Br 40 ± 16, Sr 18 ± 4, Y 4 ± 2; U. aurantiaco-atra – V 7 ± 6, Cr 6 ± 3, Mn 59 ± 35, Cu 66 ± 33, Zn 27 ± 5, Pb 5 ± 1, Br 30 ± 15, Sr 32 ± 20, Y 3 ± 3. The average concentrations of Cr, Mn and Pb in all samples from research stations demonstrated significant differences in relation to the reference material. The maximal concentrations of measured elements obtained in the samples from potentially polluted areas were as a rule much higher (~120–3800%) in comparison with the concentrations in the control group. This observation is especially worrying. These results point out that the human influence on the Antarctic environment may be negative and indicate the necessity for pollution monitoring programmes in the region. This research is a part of biomonitoring recommended by SCAR (Scientific Committee on Antarctic Research).
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