Trace-Element Interactions in Rook Corvus frugilegus Eggshells Along an Urbanisation Gradient Grzegorz Orlowski • Zbigniew Kasprzykowski • Wojciech Dobicki • Przemyslaw Pokorny • Andrzej Wuczyn ´ski • Ryszard Polechon ´ski • Tomasz D. Mazgajski Received: 10 December 2013 / Accepted: 31 March 2014 Ó Springer Science+Business Media New York 2014 Abstract Concentrations of seven trace elements [arsenic (As), chromium (Cr), nickel (Ni), lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd)] in the eggshells of Rooks Corvus frugilegus, a focal bird species of Eurasian agri- cultural environments, are increased above background levels and exceed levels of toxicological concern. The concentrations of Cr, Ni, Pb, Cu, and Zn are greater in eggshells from urban rookeries (large cities) compared with rural areas (small towns and villages) suggesting an urbanisation gradient effect among eggs laid by females. In the present study, the investigators assessed whether the pattern of relationships among the seven trace elements in eggshells change along an urbanisation/pollution gradient. Surprisingly, we found that eggshells with the greatest contaminant burden, i.e., from urban rookeries, showed far fewer significant relationships (n = 4) than eggshells from villages (n = 10), small towns (n = 6), or rural areas (n = 8). In most cases, the relationships were positive. As was an exception: Its concentration was negatively corre- lated with Ni and Cd levels in eggshells from small town rookeries (where As levels were the highest), whereas eggshells from villages (with a lower As level) showed positive relationships between As and Cd. Our findings suggest that at low to intermediate levels, interactions between the trace elements in Rook eggshells are of a synergistic character and appear to operate as parallel coaccumulation. A habitat-specific excess of some ele- ments (primarily Cr, Ni, Cu, As) suggests their more competitively selective sequestration. Despite the need for better knowledge of elemental inter- actions about the toxicological assessment of wildlife in the geochemical environment (Mo ¨ller 1996), avian eggs have rarely been examined or used in such analyses. In view of the indispensable part played by eggs in the reproductive process in birds, the composition and/or interaction of chemical elements present in eggs, i.e., in the egg content and shell, are of critical importance for the proper devel- opment of the embryo and body of hatching nestlings (Pinowski et al. 1994; Nys et al. 2004). The main function of the eggshell is to protect the embryo from external factors, a function that must never- theless be compatible with ready breakability from the inside to allow the hatchling to emerge. The eggshell structure must permit the exchange of water and gases between the environment and the embryo during its extrauterine development as well as be a source of calcium (Ca) for the growing embryo (Nys et al. 2004). Because eggshell is a ceramic material, some elements or chemical G. Orlowski (&) Institute of Agricultural and Forest Environment, Polish Academy of Sciences, Bukowska 19, 60-809 Poznan, Poland e-mail: orlog@poczta.onet.pl Z. Kasprzykowski Department of Ecology and Nature Protection, University of Podlasie, Prusa 12, 08-110 Siedlce, Poland W. Dobicki Á P. Pokorny Á R. Polechon ´ski Department of Hydrobiology and Aquaculture, Wroclaw University of Environmental and Life Sciences, Chelmon ´skiego 38C, 51-630 Wroclaw, Poland A. Wuczyn ´ski Institute of Nature Conservation, Polish Academy of Sciences, Lower-Silesian Field Station, Podwale 75, 50-449 Wroclaw, Poland T. D. Mazgajski Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, 00-679 Warsaw, Poland 123 Arch Environ Contam Toxicol DOI 10.1007/s00244-014-0030-x