The evolution of nestling discrimination by hosts of parasitic birds: why is rejection so rare?

摘要: Question: Why do hosts of parasitic birds defend against eggs but not nestlings? Data incorporated: Reported cases chick discrimination or mimicry and all previously published explanations for the rarity these phenomena. Method analysis: Contrasting predictions previous hypotheses fitting available data from both non-parasitic to assess relative validity each explanation. Results: None suggested appears provide a general explanation scarcity discrimination. Various cognitive behavioural traits potentially usable chicks are present in virtually avian taxa, including host lineages, yet used reject parasites. Thus, low selection pressure imposed by rare parasites is most likely absence adaptations context brood parasitism. Based on this, I predict that nestling should predominantly evolve forced accept parasite because close match between eggs. This occur due egg phylogenetic physical constraints. demonstrate evidence line with this hypothesis. Conclusion: A host’s own behaviour may play crucial role retarding escalation arms-race stage.