Organochlorine pesticides levels in eagle owl (Bubo bubo) eggs: Temporal trends and sublethal effects

According to the NRC requirements, the eagle owl could be considered a suitable sentinel species for biomonitoring organochlorine pesticides, reflecting both their use and food web transfer. In order to obtain this information from an agricultural area in Southeastern Spain, 58 unhatched eggs from the period 2004–2009 were analysed for 23 organochlorine compounds. Homogenized egg contents were processed with n-hexane, and cleaned up by GPC. Detection and quantification was performed using GC–MS. A homogeneous temporal trend was found for the total of compounds analyzed, with a significant decrease in 2008 (Chi-square = 13.31, p <0.01). On the contrary, lindane (Chi-square = 15.03, p <0.01) and DDT (Chi-square = 9.76, p <0.05) significantly increased along the whole period, reaching higher levels in 2009. Although DDT was banned in Spain in 1971, this compound has been used until 2008 for the synthesis of dicofol, an insecticide recommended for citrus farming in the study area. Previous studies in other raptor species from the same region show a positive correlation between DDT blood levels and citrus, vineyard and olive tree crops, for which dicofol was also recommended. Lindane was banned in Spain in 2000 for agricultural use, and allowed for animal use until December 2007. The increasing levels could reflect a current illegal use of this compound. Eggshell thickness is a good biomarker, inversely correlated with DDE levels in birds. A significant negative correlation was found between eggshell thickness and DDE concentration in our population (P = -0.445, p <0.01) and a 17% of thinning when DDE levels were higher than 100 µg/g (lipid weight). Although other contaminants may cause some eggshell thinning, DDE has been established as the main role.