Evol Ecol Res 8: 785-802 (2006)     Full PDF if your library subscribes.

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

Tomáš Grim*

School of Biological Sciences, University of Auckland, Auckland, New Zealand and Department of Zoology, Palacky University, Olomouc, Czech Republic

Address all correspondence to Tomáš Grim, Department of Zoology, Palacky University, tr. Svobody 26, CZ-771 46 Olomouc, Czech Republic.
e-mail: grim@prfnw.upol.cz


Question: Why do hosts of parasitic birds defend against parasitic eggs but not nestlings?

Data incorporated: Reported cases of parasitic chick discrimination or mimicry and all previously published explanations for the rarity of these phenomena.

Method of analysis: Contrasting the predictions of previous hypotheses and fitting available data from both parasitic and non-parasitic birds to assess the relative validity of each explanation.

Results: None of the previously suggested hypotheses appears to provide a general explanation for the scarcity of chick discrimination. Various cognitive and behavioural traits potentially usable for discrimination of parasitic chicks are present in virtually all avian taxa, including host lineages, yet these traits are not used to reject parasites. Thus, low selection pressure imposed by rare parasites is the most likely general explanation for the absence of these adaptations in the context of brood parasitism. Based on this, I predict that nestling discrimination and mimicry should predominantly evolve in hosts that are forced to accept parasite eggs because of the close match between parasitic and host eggs. This is likely to occur due to egg mimicry or phylogenetic and physical constraints. I demonstrate that available evidence is in line with this rare parasite hypothesis.

Conclusion: A host’s own behaviour may play a crucial role in retarding the escalation of the arms-race to the nestling stage.

Keywords: arms-race, brood parasitism, co-evolution, discrimination, evolutionary equilibrium, evolutionary lag, recognition.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2006 Tomáš Grim. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.