Variation of uropygial gland volume and malaria infection between urban-rural environment in the house sparrow

Abstract

All the organisms have developed defensive against different (parasites, harsh environmental conditions or contaminants) to which they should face in their environments. To deal with these selective factors, birds have developed defensive mechanisms such as the uropygial gland, which produces a secretion acting as a physico-chemical defensive barrier against a high diversity of ectoparasites and prevent the potential transmission of blood parasites. Therefore, this secretion plays a fundamental role on the feather resistance to abrasion. However, there is still little knowledge about the functional adaptations of this gland to different environments. Here, we analysed the variation in uropygial gland volume in relation to different habitats (rural vs. urban) and to malaria infection in house sparrows (Passer domesticus). Our results showed that rural sparrows infected with malaria had the lowest uropygial volume. Furthermore, we found a positive relationship between uropygial gland volume and body condition, regardless of habitat, sex or prevalence of infection (infected or uninfected). These findings highlight the important role of this gland in the avian body condition and on its adaptation to different environments.