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Re: Little skulls & cuckoos

>>  The cost of cuckoo-egg-rejection behavior is that occasionally a host
bird will accidentally destroy one of its own eggs, misidentifying it as a
cuckoo egg.  There has been a fair amount of mathematical modelling &
field studies of the evolution of cuckoo egg rejection and it is partly a
trade-off of "risk of accepting cuckoo egg" vs. "risk of accidental
destruction of own egg". The risks, of course, vary with appearance &
variation of cuckoo eggs & host eggs, alertness of the host to other cues
(e.g. presence of a cuckoo female in the territory), cuckoo population &
host choice by cuckoos. Ditto for other brood parasites....
  As for symbiosis, I haven't heard of any observed benefits to hosts
from brood parasites (pipe up, anyone), while the costs (death of
offspring & "overworking" of parents) are well-documented.<<

Okay, so cukoos and their hosts are in a state of dynamic equilibrium.  I had
wondered about that, since the arrangment never seemed that stable.  How do
the host birds raise enough chicks to maintain their population?  What keeps
them from rejecting the chicks that obviously arn't theirs?  Now I have an
answer.  Thanks.