Journal of Ethology

, Volume 22, Issue 2, pp 175–180

Are blackcaps current winners in the evolutionary struggle against the common cuckoo?

Authors

    • Institute of Vertebrate BiologyAcademy of Sciences of the Czech Republic
  • Petr Procházka
    • Institute of Vertebrate BiologyAcademy of Sciences of the Czech Republic
    • Department of Zoology, Faculty of Science Charles University
  • Bård G. Stokke
    • Department of BiologyNorwegian University of Science and Technology NTNU
  • Arne Moksnes
    • Department of BiologyNorwegian University of Science and Technology NTNU
  • Eivin Røskaft
    • Department of BiologyNorwegian University of Science and Technology NTNU
  • Miroslav ČapekJr
    • Institute of Vertebrate BiologyAcademy of Sciences of the Czech Republic
  • Vojtěch Mrlík
    • Institute of Vertebrate BiologyAcademy of Sciences of the Czech Republic
Article

DOI: 10.1007/s10164-004-0119-1

Cite this article as:
Honza, M., Procházka, P., Stokke, B.G. et al. J Ethol (2004) 22: 175. doi:10.1007/s10164-004-0119-1

Abstract

Blackcaps Sylvia atricapilla reject artificial cuckoo eggs, and their eggs vary little in appearance within clutches, whereas among clutches eggs vary considerably. Low variation within clutches facilitates discrimination of parasitic eggs, whereas high variation among clutches makes it harder for the cuckoo to mimic the eggs of a certain host species. These traits have most probably evolved as counteradaptations against brood parasitism by the common cuckoo Cuculus canorus, even though blackcaps are not regularly parasitised today. In this study, we investigated how fine-tuned the rejection of parasitic eggs is in this species by introducing three types of eggs into their nests: a real non-mimetic egg the approximate size of a cuckoo egg, an artificial mimetic egg the size of a cuckoo egg and a real conspecific egg. As the rejection frequency of both mimetic and non-mimetic artificial cuckoo eggs has been shown to be high in previous studies, the variation in rejection behaviour between individuals is low, indicating that most individuals within the population are able to reject parasitic eggs. Thus, we predict that (1) the intraclutch variation in egg appearance should be generally low in all individuals, and that (2) regarding conspecific eggs, rejection decisions should be highly dependent on the degree of mimicry between parasitic and host eggs. We found support for these predictions, which indicates that due to their highly sophisticated countermeasures against brood parasitism, blackcaps can probably be regarded as current winners of the arms race with the common cuckoo. Furthermore, the high and consistent rejection frequency of cuckoo eggs found throughout Europe for this species supports the spatial habitat structure hypothesis, which claims that woodland-nesting species breeding near trees, like blackcaps, presumably experienced a high level of parasitism throughout their range in the past and, therefore, their rejection behaviour, once evolved, spread rapidly to all populations.

Keywords

BlackcapBrood parasitismCuckooCuculus canorusEgg discriminationEgg recognitionSylvia atricapillaSpatial habitat structure

Copyright information

© Japan Ethological Society and Springer-Verlag 2004