Plumage micro-organisms and preen gland size in an urbanizing context

Mathieu Giraudeau, Ryan Stikeleather, Jennifer McKenna, Pierce Hutton, Kevin McGraw

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Urbanization of Earth's habitats has led to considerable loss of biodiversity, but the driving ecological mechanism(s) are not always clear. Vertebrates like birds typically experience urban alterations to diet, habitat availability, and levels of predation or competition, but may also be exposed to greater or more pathogenic communities of microbes. Birds have been popular subjects of urban ecological research but, to our knowledge, no study has assessed how urban conditions influence the microbial communities on bird plumage. Birds carry a large variety of microorganisms on their plumage and some of them have the capacity to degrade feather keratin and alter plumage integrity. To limit the negative effects of these feather-degrading bacteria, birds coat their feathers with preen gland secretions containing antibacterial substances. Here we examined urban-rural variation in feather microbial abundance and preen gland size in house finches (Haemorhous mexicanus). We found that, although urban and rural finches carry similar total-cultivable microbial loads on their plumage, the abundance of feather-degrading bacteria was on average three times higher on the plumage of urban birds. We also found an increase in preen gland size along the gradient of urbanization, suggesting that urban birds may coat their feathers with more preen oil to limit the growth or activity of feather-degrading microbes. Given that greater investment in preening is traded-off against other immunological defenses and that feather-degrading bacteria can alter key processes like thermoregulation, aerodynamics, and coloration, our findings highlight the importance of plumage microbes and microbial defenses on the ecology of urban birds.

Original languageEnglish (US)
Pages (from-to)425-429
Number of pages5
JournalScience of the Total Environment
StatePublished - Feb 15 2017


  • Feather microbes
  • Haemorhous mexicanus
  • Urbanization
  • Uropygial gland

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution


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