Why do some female cuckoos remove host eggs from a nest?

Female cuckoos remove one or more host eggs from a nest for two primary reasons related to the success of their brood parasitism:

• Reducing competition: By removing host eggs, the female cuckoo ensures that her own offspring will face less competition from the host's nestlings for food and parental attention once they hatch.12
• Avoiding detection: Removing a host egg helps prevent the host from recognizing that a foreign egg has been added to the nest. If the host notices an increase in the total number of eggs or detects a mismatch, it is more likely to reject the parasite's egg or desert the nest entirely.2

This behavior, alongside nest-mate eviction performed by the hatched cuckoo chick, serves as a critical adaptation to ensure the survival of the parasite at the expense of the host's own brood.12