Parasitism has the parasite benefitting while the host is harmed. In Brood parasitism, the Cuckoo rests its eggs in Crow's nest for incubation. How does this harm the Host? Why not considered Ammensalism? If I see the fact, while resting its eggs, the Cuckoo might break some of Crows eggs, the eggs might break and this way the crow gets harmed. Parasitism from here fits. But, as the chicks grow, the cuckoo chicks serve protecting the Crow progenies from other bird or predator. Seeing this, yet commensalism fits. So, If I have to finalise which species interaction Brood Parasitism comes under, what should I select? And why that Interaction preferred over the other?
The cuckoo chick hatches earlier and instinctively pushes the host eggs out of the nest. If you view this from the genetic perspective of the crow, it becomes the foster parent of offspring that does not carry its genes. The harm, therefore, is to the host's passing on of genes, rather than to the immediate health or well-being of the individual.
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