Question

In an area where DDT had been used extensively, the bird population declined significantly due to

• A. birds stopped laying eggs
• B. snakes started feeding exclusively on birds
• C. earthworms disappeared from the area
• D. many of the birds eggs didn't hatch

Answer 1

The correct option is D many of the birds eggs didn't hatch

$\text{Introduction to DDT}$

DDT (Dichloro-diphenyl-trichloroethane) is a compound utilised massively as an insecticide in agriculture. However, the agricultural run off led to its discharge into the water bodies.

On being consumed by the fishes and fish-eating birds, DDT started accumulating in the tissues as it cannot be metabolised and excreted.

It causes biomagnification by accumulating in higher concentration in the feeding members of successive trophic levels

$\text{Effects of DDT on bird}$

This accumulation of DDT in birds (present at the top-most trophic level) causes the following:

• Infertility
• Disturbance in calcium metabolism
• Thinning and premature breaking of eggshells

Eventually, these resulted in decline in the bird population feeding on fishes residing in DDT-polluted waters.

$\text{Final answer}$

(c) many of the birds eggs didn't hatch