The role of egg-nest contrast in the rejection of brood parasitic eggs

Zachary Aidala, Rebecca Croston, Jessica Schwartz, Lainga Tong, Mark E. Hauber

Research output: Contribution to journalArticlepeer-review


Hosts of avian brood parasites can avoid the reproductive costs of raising genetically unrelated offspring by rejecting parasitic eggs. The perceptual cues and controlsmediating parasitic egg discrimination and ejection are well studied: hosts are thought to use differences in egg color, brightness, maculation, size and shape to discriminate between their own and foreign eggs. Most theories of brood parasitism implicitly assume that the primary criteria to which hosts attend when discriminating eggs are differences between the eggs themselves. However, this assumption is confounded by the degree to which chromatic and achromatic characteristics of the nest lining co-vary with egg coloration, so that egg-nest contrast per semight be the recognition cue driving parasitic egg detection. Here, we systematically tested whether and how egg-nest contrast itself contributes to foreign egg discrimination. In an artificial parasitism experiment, we independently manipulated egg color and nest lining color of the egg-ejector American robin (Turdus migratorius), a host of the obligate brood parasitic brown-headed cowbird (Molothrus ater). We hypothesized that the degreeof contrast between foreign eggsand the nest backgroundwould affect host egg rejection behavior. We predicted that experimentally decreasing egg-nest chromatic and achromatic contrast (i.e. rendering parasitic eggs more cryptic against the nest lining) would decrease rejection rates, while increasing egg-nest contrast would increase rejection rates. In contrast to our predictions, egg-nest contrast was not a significant predictor of egg ejection patterns. Instead, egg color significantly predicted responses to parasitism. We conclude that egg- egg differences are the primary drivers of egg rejection in this system. Future studies should test for the effects of egg-nest contrast per se in predicting parasitic egg recognition in other host-parasite systems, includingthose hosts building enclosed nestsandthoseparasites laying cryptic eggs, as an alternative to hypothesized effects of egg-egg contrast.

Original languageEnglish (US)
Pages (from-to)1126-1136
Number of pages11
JournalJournal of Experimental Biology
Issue number8
StatePublished - Apr 15 2015
Externally publishedYes


  • Brood parasitism
  • Egg rejection
  • Visual ecology
  • Visual modeling

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science


Dive into the research topics of 'The role of egg-nest contrast in the rejection of brood parasitic eggs'. Together they form a unique fingerprint.

Cite this