Microbiota and the volatile profile of avian nests are associated with each other and with the intensity of parasitism

Abstract

Bacteria have been suggested as being partially responsible for avian nest odours and, thus, v olatiles fr om their meta bolism could influence the intensity of selection pr essur es due to parasites detecting olfactory cues of their hosts. Here , w e tested this hypothesis by exploring intraspecific and interspecific v aria bility in micr obial envir onments, v olatile pr ofiles and intensity of ectoparasitism by Carnus hemapterus in the nests of 10 avian species. As expected, we found that (i) alpha and beta di v ersity of micr obial and v olatile pr ofiles wer e associated with each other. Mor eov er, (ii) alpha di v ersity of bacteria and volatiles of the nest environment, as well as some particular bacteria and v olatiles, w as associated with the intensity of parasitism at early and late stages of the nestling period. Finally, (iii) alpha di v ersity of the nest microbiota, as well as some particular bacteria and v olatiles, w as corr elated with fledging success. When considering them together, the results support the expected links between the microbial environment and nest odours in different bird species, and between the microbial environment and both ectoparasitism intensity and fledging success. Relati v e a bundances of particular volatiles and bacteria predicted ectoparasitism and/or fledging success. Future resear c h should prioritise experimental appr oaches dir ected to determine the r ole of bacteria and v olatiles in the outcomes of host–ectopar asite inter actions.