Autoclaving Nest-Material Remains Influences the Probability of Ectoparasitism of Nestling Hoopoes (Upupa epops)

Abstract

Nest bacterial environment influences avian reproduction directly because it might include pathogenic- or antibiotic-producing bacteria or indirectly because predators or ectoparasites can use volatile compounds from nest bacterial metabolism to detect nests of their avian hosts. Hoopoes (Upupa epops) do not build nests. They rather reuse holes or nest-boxes that contain remains of nest-materials from previous breeding seasons. Interestingly, it has been recently described that the nest’s bacterial environment partly affects the uropygial gland microbiota of hoopoe females and eggshells. Blood-sucking ectoparasites use chemical cues to find host nests, so we experimentally tested the hypothetical effects of microorganisms inhabiting nest-material remains before reproduction regarding the intensity of ectoparasitism suffered by 8-day-old nestling hoopoes. In accordance with the hypothesis, nestlings hatched in nest-boxes with autoclaved nest-material remains from the previous reproductive seasons suffered less from ectoparasites than those hatched in the control nest-boxes with nonautoclaved nest-material. Moreover, we found a positive association between the bacterial density of nest-material during the nestling phase and ectoparasitism intensity that was only apparent in nest-boxes with autoclaved nest-material. However, contrary to our expectations, nest bacterial load was positively associated with fledgling success. These results suggest a link between the community of microorganisms of nest-material remains and the intensity of ectoparasitism, and, on the other hand, that the nest bacterial environment during reproduction is related to fledging success. Here, we discuss possible mechanisms explaining the experimental and correlative results, including the possibility that the experimental autoclaving of nest material affected the microbiota of females and nestlings’ secretion and/or nest volatiles that attracted ectoparasites, therefore indirectly affecting both the nest bacterial environment at the nestling stage and fledging success.

Overwinter users of nest cavities affect breeding birds via nest‐dwelling ectoparasites

“…However, occupancy of nest boxes by dormice in February did not influence parasite loads of hoopoe nestlings, which does not support this prediction. Another nonexclusive explanation for the higher Carnus abundance found in open nest boxes during hoopoe reproduction could be that overwinter occupants deliver more olfactory cues in nest boxes, which can be used later in spring for prospecting Carnus searching for new nests to parasitize (Mazorra-Alonso et al, 2020). In conclusion, although future studies should explore possible mechanisms, our experimental results show that overwinter occupants of nest cavities have direct effects on the emergence of nest-dwelling ectoparasites and therefore on the intensity of ectoparasitism experienced by nesting birds in the following season.…”

Microbially Mediated Chemical Ecology of Animals: A Review of Its Role in Conspecific Communication, Parasitism and Predation

“…In accordance with this possibility, the experimental breakage and delivery of fecal sac contents of spotless starling nestlings increased the bacterial density in their nests, and was related to an increased predation rate and ectoparasite load [ 90 ]. Similarly, nestling hoopoes developing in nest boxes where microorganisms were experimentally eliminated from nest substrates suffered reduced ectoparasite loads [ 91 ]. These results, therefore, suggest that selection pressures due to parasitism and predation should influence the evolution of host characteristics allowing the establishment of particular microbiotas that produce volatiles, which would reduce the risk of being detected by enemies.…”

“…These results, therefore, suggest that selection pressures due to parasitism and predation should influence the evolution of host characteristics allowing the establishment of particular microbiotas that produce volatiles, which would reduce the risk of being detected by enemies. This interesting possibility could be tested by performing experiments known to influence both the bacterial community of avian nests and the risk of parasitism experienced by nestlings (e.g., breakage of nestling feces, addition of feathers or aromatic plants to the nest, or autoclaving nest material before reproduction [ 90 , 91 , 92 , 93 , 94 ]). Differences in risk of parasitism experienced by nests under different experimental treatments should covary with differences in microbiotas and volatile profiles.…”