title: Feather bacterial load shapes the trade-off between preening and immunity in pigeons.
abstract: BACKGROUND
  Complex communities of bacteria inhabit the feathers of all birds. Under normal conditions, individuals maintain a healthy state by defending themselves against these potential invaders by preening. The immune system is only triggered when bacteria gain access into the body. Preening is, however, costly and may trade-off with investment in the immune system. To shed light on how birds balance the trade-off between immunity and preen secretions when facing high or low feather bacterial load, we experimentally manipulated feather bacteria load of feral pigeons (Columba livia), and investigated the effects on immune defenses.
  
  
  RESULTS
  Birds facing high feather bacterial load had lower immune response to PHA skin-swelling test (a measure of induced pro-inflammatory capacity) than controls, while birds facing low feather bacterial load had higher blood bacterial killing ability (a measure of the capacity to eliminate bacterial pathogens) than controls. No other components of the immune system (i.e., hemagglutination and hemolysis capacity of plasma, primary and secondary responses to KLH and quantity of blood parasites) were found to be affected by feather bacterial load.
  
  
  CONCLUSIONS
  Pigeons had previously been shown to adjust preening to feather bacterial load. The decrease in the energetically costly inflammatory response of birds experiencing high bacterial load suggests a trade-off between investment in preen secretion and immunity and reinforces the idea that feather microbiota may have a strong impact on the ecology and evolution of the avian host.
authors.affiliation: Sorbonnes Universités, UPMC Université Paris 06, Institut d'Ecologie et des Sciences de l'Environnement de Paris, Paris, F-75005, France. sarah.leclaire@free.fr.|CEFE-CNRS, UMR5175, Centre d'Ecologie Fonctionnelle et Evolutive, 1919 Rte de Mende, Montpellier, 34293, France. sarah.leclaire@free.fr.
authors.forename: Sarah
authors.initials: S
authors.lastname: Leclaire
authors.affiliation: Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, Berlin, 10315, Germany. czirjak@izw-berlin.de.
authors.forename: Gábor Árpád
authors.initials: GÁ
authors.lastname: Czirják
authors.affiliation: Département des Sciences de la Vie, Faculté des Sciences de Gabès, Cité Erriadh, Zrig 6072, Gabès, Tunisia. h_abdesslem@yahoo.fr.
authors.forename: Abdessalem
authors.initials: A
authors.lastname: Hammouda
authors.affiliation: Sorbonnes Universités, UPMC Université Paris 06, Institut d'Ecologie et des Sciences de l'Environnement de Paris, Paris, F-75005, France. jgasparini@snv.jussieu.fr.
authors.forename: Julien
authors.initials: J
authors.lastname: Gasparini
mesh_terms: D000818:Animals; D058491:Bacterial Load; D005075:Biological Evolution; D010856:Columbidae / Q000276:immunology / Q000382:microbiology / Q000502:physiology*; D005241:Feathers / Q000382:microbiology*; D006120:Grooming; D006433:Hemocyanins / Q000276:immunology; D007249:Inflammation / Q000276:immunology; D010835:Phytohemagglutinins / Q000276:immunology
chemical_list: D010835:Phytohemagglutinins; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin