Question

unusual bird parenting
birds have a reputation as excellent parents. they expend a great deal of effort in building nests in which to lay their eggs. they patiently incubate the eggs, keeping them warm and safe until they hatch. birds also bring food to their newly hatched offspring until the baby birds are independent. however, some unusual birds, known as brood parasites, dont provide any parental care for their young. perhaps the most famous brood parasite is the cuckoo. instead of building a nest, the cuckoo lays her eggs in the nest of another species with similar - looking eggs. the female cuckoo simply removes an egg laid by the host female, lays her own egg, and then leaves, expecting the host bird to care for the imposter.
what is the main, or central, idea of the passage?
most birds build nests for their young, incubate the eggs, and are generally devoted parents.
unlike most species of birds, brood parasites such as the cuckoo dont build nests.
unlike most species of birds, brood parasites such as the cuckoo dont provide any parental care.

Explanation:

The passage first mentions that most birds are excellent parents (building nests, incubating eggs, feeding offspring). Then it uses "However" to introduce brood parasites (like cuckoos) which are different - they don't provide parental care. The first option only focuses on most birds, not the contrast. The second option only mentions not building nests (a part of not providing parental care). The third option captures the main contrast (most birds vs brood parasites in terms of parental care).

Answer:

Unlike most species of birds, brood parasites such as the cuckoo don't provide any parental care.