Absence of anti-parasitic defenses in an Asian population of the magpie, a regular host of the great spotted cuckoo in Europe

Obligate brood parasitism,which refers to parasitic birds,fish,and insects that lay eggs in host nests,imposes strong selective pressure on hosts because the reproductive output of hosts is reduced considerably or eliminated completely while the foster parents provide extra-parental care to unrelated nestlings(Soler 2016).After parasites succeed in laying eggs,egg rejection by hosts plays an important role in avoiding parasitism by recognition and rejection of parasite eggs from host nests(Yang et al.2014).