Different recognition cues reveal the decision rules used for egg rejection by hosts of a variably mimetic avian brood parasite

M. Alicia de la Colina, Lorena Pompilio, Mark E. Hauber, Juan C. Reboreda, Bettina Mahler

Research output: Contribution to journalArticlepeer-review

Abstract

Brood parasitism imposes several fitness costs on the host species. To reduce these costs, hosts of avian brood parasites have evolved various defenses, of which egg rejection is the most prevalent. In the face of variable host-parasite mimicry and the costs of egg discrimination itself, many hosts reject only some foreign eggs. Here, we experimentally varied the recognition cues to study the underlying cognitive mechanisms used by the Chalk-browed Mockingbird (Mimus saturninus) to reject the white immaculate eggs laid by the parasitic Shiny Cowbird (Molothrus bonariensis). Immaculate eggs are the only parasite eggs rejected by this host, as it accepts all polymorphic, spotted eggs laid by cowbirds. Using a within-breeding pair experimental design, we tested for the salience of spotting, UV reflectance, and brightness in eliciting rejection. We found that the presence of spotting significantly decreased the probability of rejection while increments in brightness significantly increased rejection frequencies. The cognitive rules underlying mockingbird rejection behavior can be explained by a decision-making model which predicts changes in the levels of rejection in direct relation to the number of relevant attributes shared between host and parasite eggs.

Original languageEnglish (US)
Pages (from-to)881-889
Number of pages9
JournalAnimal cognition
Volume15
Issue number5
DOIs
StatePublished - Sep 2012
Externally publishedYes

Keywords

  • Antiparasite defenses
  • Chalk-browed Mockingbird
  • Egg rejection
  • Eggshell spotting
  • Shiny Cowbird

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Experimental and Cognitive Psychology

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