Ed Yong in Not Exactly Rocket Science:
The common cuckoo is famed for its knack for mooching off the parental instincts of other birds. It lays its eggs in the nests of at least 100 other species, turning them into inadvertent foster parents for its greedy chicks. For this reason, it’s called a brood parasite.
It’s not alone. Among the birds, the full list of brood parasites includes more than 50 members of the cuckoo family, cowbirds, honeyguides, several finches, and at least one duck.
Now, William Feeney from the Australian National University has found that brand of reproductive cheating goes hand in hand with its polar opposite: cooperative breeding, where birds raise their young with help from siblings or offspring, often at the cost of the helpers’ own reproductive success.
The two strategies couldn’t be more different but Feeney found that each drives the evolution of the other. In places where one is common, the other is too. Exploitation goes hand-in-hand with cooperation.