Which of the following is right time to watch 'brood-parasitism' in nature ?

Spring to summer.

Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host and lets the host incubate them.

During the course of evolution, the eggs of the parasitic bird have evolved to resemble the host’s egg in size and colour to reduce the chances of the host bird detecting the foreign eggs and ejecting them from the nest. We can see the movements of the cuckoo (koel) and the crow during the breeding season (spring to summer) and watch brood parasitism in action.