Evidence for egg discrimination preceding failed rejection attempts in a small cuckoo host
TLDR
This is the first demonstration of a cuckoo host discriminating against real parasitic eggs but often accepting them, and results show that in host species experiencing difficulties in performing puncture ejection, non-mimetic cuckoos eggs may avoid rejection by means of their unusually high structural strength.Abstract:
Given the high costs of avian obligate brood parasitism, host individuals are selected to reject parasitic eggs they recognize as foreign. We show that rejection may not necessarily follow egg discrimination when selective removal of the parasitic egg is difficult. We studied egg rejection behaviour in a small host of the common cuckoo Cuculus canorus, the eastern olivaceous warbler Hippolais pallida, by experimental parasitism with model and real non-mimetic cuckoo eggs and video recordings of host behaviour. Hosts pecked 87 per cent (20 out of 23) of the model eggs but eventually accepted 43.5 per cent (10 out of 23) of them. A similar pattern was found for real cuckoo eggs, which were all pecked, but as many as 47 per cent (7 out of 15) of them were accepted. To our knowledge, this is the first demonstration of a cuckoo host discriminating against real parasitic eggs but often accepting them. Our results also show that in host species experiencing difficulties in performing puncture ejection, non-mimetic cuckoo eggs may avoid rejection by means of their unusually high structural strength.read more
Citations
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Alternative mechanisms of increased eggshell hardness of avian brood parasites relative to host species
Branislav Igic,Kim Braganza,Margaret Hyland,Heather Silyn-Roberts,Phillip Cassey,Phillip Cassey,Tomáš Grim,Jarkko Rutila,Csaba Moskát,Mark E. Hauber,Mark E. Hauber +10 more
TL;DR: Eggshell characteristics did not differ between parasite eggs sampled from different host nests in distant geographical sites, suggesting an evolutionarily shared microstructural mechanism of stronger parasite eggshells across diverse host-races of brood parasitic cuckoos.
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Could a factor that does not affect egg recognition influence the decision of rejection
TL;DR: The authors' results showed that blackbirds more frequently accepted heavy eggs, even when previously recognized, and this differential acceptance may be related to insufficient motivation to assume the higher costs that the ejection of a heavy egg could impose.
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How to Spot a Stranger's Egg? A Mimicry-Specific Discordancy Effect in the Recognition of Parasitic Eggs
Csaba Moskát,Csaba Moskát,Anikó Zölei,Miklós Bán,Zoltán Elek,Zoltán Elek,Lainga Tong,Nikoletta Geltsch,Mark E. Hauber +8 more
TL;DR: The results imply that in addition to sensory filters, and template-based cognitive decision rules, discordancy-based rejection is affected by the overall clutch appearance and interacts with specific colours varying in the extent of mimicry, to contribute to the recognition decisions of hosts to reject parasitic eggs.
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The Limits of Artificial Stimuli in Behavioral Research: The Umwelt Gamble
TL;DR: In this article, the authors outline limitations and pitfalls associated with the use of artificial stimuli in behavioral experimentation and suggest that researchers should weigh the advantages of using artificial stimuli against the risks in any particular case.
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True recognition of nestlings by hosts selects for mimetic cuckoo chicks
TL;DR: It is found that gerygones use true template-based recognition based on at least one visual chick trait (the number of hatchling down-feathers) that has facilitated the evolution of very rapid hatchling rejection and, in turn, striking visual mimicry of host young by little bronze-cuckoo chicks.
References
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An experimental study of co-evolution between the cuckoo, cuculus canorus, and its hosts. ii. host egg markings, chick discrimination and general discussion
TL;DR: The variation in rejection of unlike eggs among different species of suitable cuckoo hosts is not related to the current costs or benefits of rejecting cuckoos, and it is suggested that the variation represents snap shots in evolutionary time of different stages of a species.
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Behavioural Responses of Potential Hosts Towards Artificial Cuckoo Eggs and Dummies
TL;DR: The results of this study lend support to the hypothesis that the differences in the degree of responses by the host species towards parasitism by the cuckoo reflect different stages in a continuous coevolutionary arms race with cuckoos.
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Recognition Errors and Probability of Parasitism Determine Whether Reed Warblers Should Accept or Reject Mimetic Cuckoo Eggs
TL;DR: It is shown that below a threshold of 19-41% parasitism, the warblers should accept mimetic cuckoo eggs because the costs of rejection outweigh the benefits, whereas above this threshold they should reject.
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Rejection Behavior by Common Cuckoo Hosts Towards Artificial Brood Parasite Eggs
TL;DR: The puncture resistance hypothesis proposed to explain the adaptive value (or evolution) of strength in cowbird eggs is supported and has received support from Picman and Rohwer et al.