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though if they fall for that they deserve all the bad luck they get.
One theory
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There is a question as to why the majority of the hosts of brood parasites care for the nestlings of their parasites. Not only do these brood parasites usually differ significantly in size and appearance, but it is also highly probable that they reduce the reproductive success of their hosts. The "mafia hypothesis" proposes that when a brood parasite discovers that its egg has been rejected, it destroys the host's nest and injures or kills the nestlings. The threat of such a response may encourage compliant behavior from the host.
https://en.wikipedia.org/wiki/Brood_parasitism
https://en.wikipedia.org/wiki/Brood_parasitism










