Sibling competition induces stress independent of nutritional status in broods of upland buzzards

Reuven Yosef, Sundev Gombobaatar, Gary R. Bortolotti

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


In any evaluation of the health and well-being of wildlife, whether to test biological theory or evaluate conservation problems, it is imperative to know to what degree variables are operating independently. Too often, important ecological and physiological traits such as body mass, immune function, and blood parameters may have a common agent influencing them; one example is glucocorticoids (corticosterone in birds) secreted in response to environmental stressors. We evaluated the nutritional condition of broods of Upland Buzzards (Buteo hemilasius) in Mongolia using ptilochronology, a measure of growth rate of feathers, and the amount of corticosterone in feathers as a long-term integrated measure of the response to stressors. Absolute amount of feather corticosterone was not significantly related to food supply, attributes of the brood, or feather growth rate. However, the relative amount of corticosterone of junior nestlings vs. their senior siblings increased as the age difference between them increased. Similarly, in the study area with larger broods where more sibling competition likely existed, junior siblings showed relatively higher amounts of stress. Our results suggested that stress seemed to be associated with sibling conflicts, and not a product of the consequences of the nutritional condition of the individuals.

Original languageEnglish
Pages (from-to)127-132
Number of pages6
JournalJournal of Raptor Research
Issue number2
StatePublished - 1 Jun 2013


  • Buteo hemilasius
  • Mongolia
  • Upland Buzzard
  • corticosterone
  • nutritional condition
  • ptilochronology
  • sibling competition
  • stress


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