Question

A crane had DDT level as 5 ppm in its body. What would happen to the population of such birds? Explain giving reasons.

Answer 1

The crane population would decline drastically.

Reasons:

1. DDT accumulates through biological magnification - it is non-biodegradable and gets concentrated at each trophic level.
2. High DDT levels cause thinning of eggshells, leading to eggs breaking during incubation.
3. This results in death of young birds before hatching, causing marked decline in population (as observed in fish-eating birds like ducks in USA in 1960s).