The DDT (dichloro-diphenyl-trichoroethane) is a pesticide that can provoke direct impact in mortality of some birds by poisoning their nervous system (robins being one of those species). The DDT can also lead to eggs with thin shells and decrease of the female hormone in birds that is used to lay eggs. The earthworms are direct affect by the pesticide, making it accumulation in the food chain, and since the earthworms are one of the food sources for robins in this food chain it is expected that with the increasing in DDT used in the environment will lead to a increase in the decrease of the robins population, since the pesticide is passed through the trophic levels of this environment.
