1. The shell of this pelican egg is unusually thin, and has already developed hairline cracks. Why are thin eggshells a hazard for pelicans and other birds?

  2. The powerful insecticide DDT (now outlawed in the U.S.) was linked to thinning eggshells in pelicans in the 1960s, when this photograph was taken. Most other birds affected by DDT were raptors. What are raptors?

  3. Pelicans and raptors are near the top of their food chains. Why do you think they suffered more dramatic effects from DDT (such as thinning eggshells) than lower-level predators such as chickens and quail?

biomagnification
Noun

process in which the concentration of a substance increases as it passes up the food chain.

concentration
Noun

measure of the amount of a substance or grouping in a specific place.

DDT
Noun

(dichloro-diphenyl-trichloroethane) toxic chemical used as an insecticide but illegal for most uses in the U.S. since 1972.

Noun

group of organisms linked in order of the food they eat, from producers to consumers, and from prey, predators, scavengers, and decomposers.

hazard
Noun

danger or risk.

nest
Noun

protected area built by birds to hatch their eggs and raise their young.

pesticide
Noun

natural or manufactured substance used to kill organisms that threaten agriculture or are undesirable. Pesticides can be fungicides (which kill harmful fungi), insecticides (which kill harmful insects), herbicides (which kill harmful plants), or rodenticides (which kill harmful rodents.)

predator
Noun

animal that hunts other animals for food.

primary consumer
Noun

organism that eats plants or other autotrophs.

raptor
Noun

bird of prey, or carnivorous bird.

secondary consumer
Noun

organism that eats meat.

tertiary consumer
Noun

carnivore that mostly eats other carnivores.