Accumulation of organochlorines and brominated flame retardants in the eggs and nestlings of great tits, Parus major.

Insectivorous birds may be very useful sentinels for local point-source contamination with persistent pollutants, such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs). Eggs have been used extensively to monitor lipophilic contaminants, as females can pass contaminants stored in their body tissues into their eggs. Concentrations and profiles in eggs therefore relate to contamination in the female. Because nestlings are raised on food items collected locally, it is expected that the body burden in nestlings would reflect their diet and local pollution levels better than eggs. In this study we compared the accumulation and the profile of PCBs, PBDEs, and OCPs in great tit (Parus major) eggs, nestlings (5-, 10-, and 15-days old), and their food in two study sites. Our results showed that concentrations in great tit eggs were 4 to 6 times higher than those in nestlings. Concentrations in nestling great tits corresponded with concentrations predicted by a bioenergetics-based model. Most of the persistent organic pollutants in 15-day old nestlings were still from maternal origin. The profile of these persistent pollutants in eggs and nestlings also gradually changed during development. With increasing age, the proportion of the most persistent compounds decreased. This study shows that most of the persistent pollutants in fully grown nestlings may still be from maternal origin. For nestlings to be suitable as indicators of local contamination, most of the POPs they accumulate should originate from dietary sources rather than from maternal transfer via the egg. Nestling birds may therefore not be good sentinels for local contamination with persistent pollutants.