Could a Factor That Does Not Affect Egg Recognition Influence the Decision of Rejection?

Rejection of the parasitic egg is the most important defence of hosts against brood parasites. However, this response is variable among and within species, and egg discrimination is not always followed by egg rejection. Low risk of parasitism and high risk of rejection costs may lead to the acceptan...

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Bibliographic Details
Published in:PloS one 2015-08, Vol.10 (8), p.e0135624-e0135624
Main Authors: Ruiz-Raya, Francisco, Soler, Manuel, Sánchez-Pérez, Lucía Ll, Ibáñez-Álamo, Juan Diego
Format: Article
Language:English
Subjects:
Animal behavior
Animal cognition
Animals
Cognitive ability
Color
Competitive Behavior - physiology
Costs
Cuculus canorus
Ecology
Eggs
Ejection
Female
Genetic aspects
Host-Parasite Interactions
Host-parasite relationships
Motivation
Nesting Behavior - physiology
Nests
Parasites
Parasitism
Pattern Recognition, Visual - physiology
Physiological aspects
Recognition, Psychology
Rejection
Songbirds - physiology
Studies
Turdus merula
Weight reduction
Zoology
Zygote - parasitology
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Summary:Rejection of the parasitic egg is the most important defence of hosts against brood parasites. However, this response is variable among and within species, and egg discrimination is not always followed by egg rejection. Low risk of parasitism and high risk of rejection costs may lead to the acceptance of the parasitic egg even if it has been previously recognized. The main aim of this paper is to answer a relevant question: can a single egg trait provoke the acceptance of an experimental egg previously recognized as foreign? Increased egg mass should hamper the ejection of an egg that has been discriminated because ejection of a heavy egg may imply higher rejection costs for hosts. We have tested this prediction by experimentally parasitizing natural nests of Common Blackbirds (Turdus merula) with non-mimetic model eggs of different mass (heavy, normal-weight, and light) while controlling for potential confounding factors such as egg size and colour. Our results showed that blackbirds more frequently accepted heavy eggs, even when previously recognized. This differential acceptance may be related to insufficient motivation to assume the higher costs that the ejection of a heavy egg could impose.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0135624