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Ornithologists observed decline in the bird population in an area near a lake after the setting of an industrial unit in the same area.

Explain the cause responsible for the decline observed.


1. DDT must have entered the trophic levels of food chain (biomagnification).

2. It was accumulated in the birds as it can neither be metabolised nor excreted.

3. High concentration of DDT disturbs calcium metabolism in birds which causes thining of the egg shells and their premature breaking, ultimately causing decline in bird populations.