Question

The population of birds declined in an area where DDT was extensively used. Why?

1 The birds stopped laying eggs
2 The eggs laid by the birds did not hatch
3 The snakes ate the eggs
4 The DDT spray killed all the birds

Answer 1

For an area where DDT had been used extensively, there's a likelihood of its biomagnification. Biomagnification refers to an increase in concentration of toxic substances due to its accumulation at successive trophic levels. Biomagnification of DDT disturbs calcium metabolism in birds leading to thinning of eggshells and its premature breaking or underdevelopment ceasing its hatching. This leads to a significant decrease in their population.

So, the correct answer is option C, many of the birds eggs did not hatch.