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Paper tests the hypothesis that urban kestrels (Falco tinnunculus) are sex biased connected with urbanization gradient (central zone vs suburbs), laying date and level of PCBcontamination. Blood samples of 158 nestlings were collected on FTA cards. Sex of nestlings was determined using a multiplex PCR technique. Egg sex ratio among kestrels in Warsaw (Poland) was 51% and did not differ significantly from parity (n = 34 nests). Among broods at the beginning and at the end of the breeding season proportion of males was significantly higher than in the middle of the season. Sex ratio was significantly different along the urbanization gradient. Proportion of males in broods at the central zone reached only 44% contrary to the external zone where males composed 65% of chicks. Possibly influence of laying date, female condition as well as population size and isolation is discussed. For assessing the level of PCBs small amount of blood (approximately 1 mm³) was collected from the brachial vein from 83 individuals (17 nests). All samples from a particular nest were pooled together to increase the possibility of successful analysis. Among most broods (pooled data for nests with complete and partial hatching) contamination of PCBs in nestlings’ blood was low (average level of PCBs was 55.1 ppm, range: 0–252.8). A trend toward decreasing proportion of males among broods with higher PCB-contamination was found to be insignificant. Probably level of organic contamination in chicks’ blood depends more on pollution existing in rural hunting areas and is not directly connected with nest site and its close vicinity.
We investigated the spatiotemporal dynamics of a breeding bird community in the urbanized landscape of Lublin city (150 km2, 0.5 million inhabitants, SE Poland). We conducted 211 separate territory mapping surveys during 26 years (1982–2007) in 24 green areas (0.2–30.1 ha in size), distributed along an urbanization gradient. We recorded a total of 16,151 territories of 65 species. According to the estimated species richness, we detected all the species present in the studied plots. The three species community indices (species richness, Shannon-Wiener index and abundance – number of breeding pairs in census plot) increased with increasing tree stand age and area of the site, while it decreased as the proportion of biologically inactive areas increased. The three indices showed significant negative trends as the study period progressed. The mean decreasing rate was 0.2 species and 2.3 territories per year. Distance to the city centre and understorey cover negatively affected bird abundance, while they positively affected species richness and the Shannon index. Tree stand age seems to be the most important of the three indices among the analyzed explanatory variables. Our results show that the diversity of breeding avifauna in an urbanized landscape can be significantly shaped by the proper management of vegetation and size of green areas in the city. The long term decline of the three diversity indices seems to be the most important outcome of our study and requires further research and monitoring.
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