RESUMEN
In this study, we determined the concentrations of As, Cd and Pb in the shaft of all primary flight feathers from ten tawny owl (Strix aluco) specimens, with the aim of selecting which shaft of the corresponding primary feather should be used in biomonitoring surveys to enable inter-individual comparisons of the levels of these metals. The birds had died between 2006 and 2013 and their bodies were stored in the various Wildlife Recovery Centres in Galicia (NW Spain). The analyses revealed a high degree of inter-shaft variability, mainly in the concentrations of As and Cd. However, it was possible to identify the most representative samples in each case: for As, the shaft of primary flight feather number 5 (S5) (which represented 11% of the total As excreted in all of the primary flight feathers); for Cd, the shaft of primary flight feather number 2 (S2) (11% of the total excreted); and for Pb, the shaft of primary flight feather number 8 (S8) (14% of the total excreted). However, the difficulties associated with the analytical determination of these pollutants in the shaft should be taken into account when this technique is applied in biomonitoring studies.