Published information relating to changes in the chemical element content of avian eggs caused by embryonic development is extremely scarce, although it may be crucial for understanding both the presence of anthropogenic pollutants as well as physiological levels of micronutrients. We assessed the variation in concentrations of calcium (Ca) and magnesium (Mg) and nine trace elements: seven essential (chromium (Cr), copper (Cu), nickel (Ni), manganese (Mn), iron (Fe), cobalt (Co) and zinc (Zn)) and two non-essential (lead (Pb) and cadmium (Cd)) in shells and contents (both egg yolk and egg white) of embryonated and non-embryonated eggs. We investigated the eggs of the Eurasian Reed Warbler Acrocephalus scirpaceus, a large proportion of whose eggs are infertile in our study population (almost 43% of clutches contain unhatched eggs) as well as significant embryo-induced eggshell thinning at the equator of embryonated eggs. We found significantly higher concentrations (≥ 22.7%) of all the focal elements in the contents of embryonated eggs in comparison with non-embryonated eggs, and a very pronounced one for Ca (nearly twice as high). The shells of embryonated eggs contained significantly higher concentrations of Zn (104.1%), Fe (56.5%), Pb (32.8%) and Cu (28.0%) but significantly lower ones of Co (8.9%) and Ca (9.3%) than the shells of non-embryonated eggs. The simultaneous higher concentrations of all elements in the content of thinnershelled embryonated eggs suggest the parallel transfer of these elements along with Ca resorption from the shell into the egg interior during embryo formation. The higher concentration of most elements in the thinner shells of embryonated eggs may be indicative of the maternal deposition of some of these elements in a shell layer not subject to embryonic depletion, or in the eggshell membrane. Our results highlight the need for the careful selection of egg samples, which should differentiate between embryonated and non-embryonated eggs in the analytical treatment of eggs and eggshells.

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Levels of copper, zinc, and arsenic were analyzed in the Rook Corvus frugilegus eggshells from 43 breeding colonies located in different parts of Poland. The average [95% confidence interval (CI)] level of copper was found to be 8.13 (0.64-15.62) ppm, of zinc 13.81 (7.99-19.62) ppm, and of arsenic 32.57 (25.60-39.54) ppm. The concentration levels of these metals varied widely in the surveyed shells, with the difference between extreme values being 90-fold for copper, 57-fold for zinc, and 36-fold for arsenic. General linear model (GLM) analysis revealed that the accumulation of copper in eggshells from urban rookeries was significantly higher than that in eggshells from rookeries in villages [average 19.31 (4.57-43.20) vs. 2.74 (2.36-3.12) ppm, respectively]. In comparison, the concentration of zinc in eggshells of urban colonies was only close to being significantly higher than that in eggshells of rural colonies (P = 0.07), and the arsenic levels in eggshells of rural and urban colonies were similar. No significant differences were found for any of the metals between rookeries located in the areas of intensive (western Poland) and extensive (eastern Poland) agriculture. Based on a comparison of our data with published data on arsenic contamination in different biota, including tissues and bird eggs of terrestrial and aquatic animals, the level of arsenic in Rook eggshells found in our study can be regarded as extremely high and is most likely due to the widespread use of pesticides containing arsenic.

Abstract:The study was conducted on the Biała Lądecka River which is a mountain river. It is similar to many European mountain rivers in terms of hydromorphology and catchment management. The aim of this study was to determine the bioconcentration factors of heavy metals (Pb, Cd, Hg, Ni, Cr, Cu and Zn)