Feather‐degrading bacteria, uropygial gland size and feather quality in House SparrowsPasser domesticus

Abstract

2Feathers are dead integumentary structures that are prone to damage and thus show gradual degradation over the course of a year. This loss of quality might have negative fitness consequences. Feather-degrading bacteria are some of the most prevalent featherdegrading organisms, yet the relationship between feather-degrading bacteria load and flight feather quality has rarely been assessed. We studied this relationship in free-living House Sparrows during breeding and non-breeding annual lifecycle stages. We also considered the size of the uropygial gland, given the antimicrobial function of its secretions, and the effect of body condition. The number of feather holes was positively associated with feather-degrading bacteria load and was negatively related to uropygial gland size and body condition during the breeding season in both sexes. In the non-breeding season we found the same relationships, but only in females. The degree of feather wear was unrelated to any of the variables measured during the breeding season, whereas it was negatively associated with uropygial gland size and positively with feather-degrading bacteria load in the non-breeding season, but only in females. Our results suggest that feather-degrading bacteria may induce the formation of feather holes, but play only a minor role in the abrasion of flight feathers.

Chemical regulation of body feather microbiota in a wild bird

“…Indeed, experimental modifications of the nest microbiota have been shown to lead to changes of feather microbiota (Jacob, Immer, et al., ), and had significant consequences for host phenotype and fitness (Jacob et al., ). Coating feathers with secretions from the uropygial gland might allow a bird to control colonization of body feathers by environmental microorganisms to some degree (Czirjak et al., ; Fülöp et al., ; Jacob, Immer, et al., ; Møller et al., ; Ruiz‐Rodriguez, Valdivia, et al., ; Shawkey et al., ).…”

“…Almost all bird species possess an external gland, the uropygial gland, which produces oily secretions used to coat feathers. Well known for their waterproofing properties (Jacob & Ziswiler, 1982) and their role in plumage signalling and communication (Lopez-Rull, Pagan, & Macias Garcia, 2010;Piault et al, 2008;Piersma, Dekker, & Sinninghe Damst e, 1999), these secretions have also been suggested to function as an antimicrobial defence mechanism used to regulate bacterial communities on feathers (Czirjak et al, 2013;F€ ul€ op, Czirj ak, Pap, & V ag asi, 2016;Jacob, Immer, et al, 2014;Leclaire, Pierret, Chatelain, & Gasparini, 2014;Mart ın-Vivaldi et al, 2009;Møller, Czirjak, & Heeb, 2009;Shawkey, Pillai, & Hill, 2003). Accordingly, by experimentally manipulating great tit (Parus major) microbiota, Jacob, Immer, et al (2014) demonstrated that individuals modify the quantity and chemical composition of uropygial secretions produced depending on their exposure to bacteria.…”

Uropygial gland volume and malaria infection are related to survival in migratory house martins

“…Because feather damage could decrease flight performance, body insulation and fitness (Proctor and Lynch , Barbosa et al ), birds with compromised feather condition should have lower survival prospects (Booth et al , Clayton et al , but also see Merilä and Hemborg ). Uropygial glands may play an essential role in the regulation of feather‐degrading bacteria, thus minimizing the impact of these pathogens on feather quality (Fülöp et al , but also see Czirják et al 2013 and Giraudeau et al for opposite results). Consequently, birds with larger uropygial glands should have better plumage condition and therefore enjoy higher survival prospects.…”

“…In this sense, birds chronically infected with malaria develop more severe clinical disease when co‐infected with Mycoplasma (Dhondt et al ). Because larger uropygial glands may prevent bacterial infection (Fülöp et al ), infected house martins secreting higher volumes of uropygial oil may prevent deadly co‐infections with malaria and bacteria. However, we should be cautious in our conclusions because our results rely on comparisons with low sample size of malaria infected house martins that survived to the next breeding season (n = 5) (Lemoine et al ).…”

“…The uropygial gland is a holocrine gland exclusive to birds secreting waxes that are smeared on the plumage during preening as part of plumage maintenance (Jacob and Ziswiler ). Although its role is still debated (see Moreno‐Rueda for a review), this secretion has been proposed to act as defensive barrier of skin and plumage in the fight against bacteria and fungi (Jacob and Ziswiler , Jacob et al , Fülöp et al ). Even though the results from some studies do not support a potential role of avian uropygial gland secretions avoiding haemosporidian vectors (Fallis and Smith , Russell and Hunter , Martínez de la Puente et al ), it has been recently suggested that uropygial secretion may prevent birds from acquiring haemosporidian infections (Magallanes et al ) because it may affect the interaction between birds and their vectors.…”