Beak colour reflects circulating carotenoid and vitamin A levels in spotless starlings (Sturnus unicolor)

Carlos Navarro, Tomás Pérez-Contreras, Jesús M. Avilés, Kevin McGraw, Juan J. Soler

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Many colourful sexually selected signals in animals are carotenoid-dependent and, because carotenoids function as antiradicals and immunostimulating molecules, carotenoid-dependent signals may honestly reflect the health state of individuals. Some others nutrients like vitamin A may also enhance health and colouration, but these have rarely been tested alongside carotenoids in colourful birds. Here, we examined whether beak colour of the spotless starling (Sturnus unicolor) reflected circulating levels of carotenoids and/or vitamin A (retinol). Spotless starlings are polygynous, sexually dimorphic birds (i. e. length of chest feathers). The tip of the beaks of male and female spotless starlings is more intensely coloured at the beginning of the breeding season and becomes dull after mating, which may suggest a sexual function. We found that females have a more intensely coloured beak and higher plasma carotenoid concentration than males during mating, and, despite the finding that carotenoid and vitamin A levels were not significantly related; colour intensity was positively correlated with plasma concentration of carotenoids and vitamin A in both sexes. However, adult beak coloration was not associated with carotenoid and vitamin A concentrations after nestlings were hatched. Therefore, beak colouration of spotless starlings provides information about circulating levels of carotenoids and vitamins during the mating season and may potentially function as a reliable signal of physiological status in the context of sexual selection.

Original languageEnglish (US)
Pages (from-to)1057-1067
Number of pages11
JournalBehavioral Ecology and Sociobiology
Issue number7
StatePublished - 2010


  • Antioxidant
  • Beak colouration
  • Plasma carotenoids
  • Plastic signals
  • Retinol
  • Sex differences
  • Vitamin A

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


Dive into the research topics of 'Beak colour reflects circulating carotenoid and vitamin A levels in spotless starlings (Sturnus unicolor)'. Together they form a unique fingerprint.

Cite this