Lichens in the nests of European starling Sturnus vulgaris serve a mate attraction rather than insecticidal function

The European starling Sturnus vulgaris is a hole-nesting bird in which the male builds a voluminous nest using a wide variety of materials such as twigs, grass, leaves, feathers, and lichens. The function of lichens in starling nests has not been assessed until now and we hypothesize that this material is related to a mate attraction function or is used to protect nestlings from parasites due to the presence of secondary compounds with insecticidal effects with the lichens. We aimed to identify the lichen species and frequency of lichen use in European starling nests, and to determine if the presence of this material is correlated with mate attraction or with an insecticidal function. We found lichens in 45% of nests, mainly represented by Ramalina celastri. The lichens were added to the nests mainly before the beginning and at the end of nest building and egg-laying started earlier in nests with lichens than those without lichens. No association was found between the presence of lichen and the intensity of Philornis larvae (Diptera), a parasite that infests starling nestlings. Our results suggest that the addition of lichens could be related to mate attraction and a stimulus for the beginning of egg-laying but did not have an antiparasitic function in European starling nests.