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Nest building and nest site selection of the Black-billed magpie Pica pica sericea were studied in Beijing, China, during 2004China, during -2006. A total of 814 Magpie nests have been checked and measured. The results showed that the first nest building occurred at the end of December, but most pairs started in February. Mostly, a new nest was built for each nesting attempt; sometimes an old nest was renovated. Magpies mobbed potential predators very intensively during the breeding season, especially congeners. Magpies build nests in strong and tall trees (51% of all nests in Populus sp.). If there is no suitable tree for building, they also build their nests on man-made constructions, such as telegraph poles, water towers, etc. Nests were always located in the upper part of the crown, domed and with one or two entrances. Four types of habitat were identified in this study: urban residential area, urban park, suburban area, and exurb. Analysis of the factors that may affect nest site selection in different habitats indicated that the height of the nesting tree was the most important one. From the outer exurb to the city centre, with the increasing number of people and cars, the height of the trees Magpies chose for nesting increased accordingly. Magpies can find enough food and face less predation pressure in the urban area, which enables them to breed successfully in the urban environment of Beijing.

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Abstract. TSP and PM2.5 aerosol samples were synchronously collected at six sites along the transport pathway of dust storm from desert regions to coastal areas in the spring of 2004. The aerosol concentration and composition were measured to investigate the regional characteristics of spring Asian dust and its impact on aerosol chemistry over northern China. Based on the daily PM10 concentrations in 13 cities, the northern China could be divided into five regions, i.e., Northern Dust Region, Northeastern Dust Region, Western Dust Region, Inland Passing Region, and Coastal Region. Northern Dust Region was characterized by high content of Ca and Northeastern Dust Region was characterized by low one instead. Northeastern Dust Region was a relatively clean area with the lowest concentrations of pollutants and secondary ions among all sites. Inland Passing Region and Coastal Region showed high concentrations of pollutants, of which As and Pb in Inland Passing Region, and Na+, SO42− and NO3− in Coastal Region were the highest, respectively. The impact of dust on air quality was the greatest in the cities near source regions, and this impact decreased in the order of Yulin/Duolun > Beijing > Qingdao/Shanghai as the increase of transport distance. The spring Asian dust was inclined to affect the chemical components in coarse particles near source regions and those in fine particles in the cities far from source regions. Dust storm could mix significant quantities of pollutants on the pathway and carry them to the downwind cities or dilute the pollutants in the cities over northern China. Each dust episode corresponded to a low ratio of NO3−/SO42− with the lowest value appearing after the peak of dust storm. Asian dust played an important role in buffering and neutralizing the acidity of atmosphere in the cities over northern China, which could lead to the pH in the aerosols increase ~1 in spring.

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