Levels of major organochlorine contaminants in sequentially - laid Herring Gull eggs

Sequentially laid eggs of Herring Gulls in Lake Erie and the Detroit River (Ontario) were found to contain increasingly higher levels of organochlorine contaminants. The reason for this was not determined but a depletion of lipid pools during the egg laying period and a rapid equilibrium between body and egg burdens may explain the results. It is recommended that, for long term toxic residue monitoring, eggs at the same position in the order of laying be taken from all sampled clutches.