Darwin's finches treat their feathers with a natural repellent.

Arno Cimadom,Dong H Cha,Rebecca Hood-Nowotny,Birgit Fessl,Erwin Nemeth,David Damiens,Elizabeth M Semler,Alejandro E Mieles,Charlotte Causton,Piedad Lincango,Stephen A Teale,Sabine Tebbich

doi:10.1038/srep34559

Abstract

Darwin’s finches are highly innovative. Recently we recorded for the first time a behavioural innovation in Darwin’s finches outside the foraging context: individuals of four species rubbed leaves of the endemic tree Psidium galapageium on their feathers. We hypothesised that this behaviour serves to repel ectoparasites and tested the repellency of P. galapageium leaf extracts against parasites that negatively affect the fitness of Darwin’s finches, namely mosquitoes and the invasive hematophagous fly Philornis downsi. Mosquitoes transmit pathogens which have recently been introduced by humans and the larvae of the fly suck blood from nestlings and incubating females. Our experimental evidence demonstrates that P. galapageium leaf extracts repel both mosquitoes and adult P. downsi and also inhibit the growth of P. downsi larvae. It is therefore possible that finches use this plant to repel ectopoarasites.

Highlights

Species Warbler finch (Certhidea olivacea) Warbler finch (Certhidea olivacea) Warbler finch (Certhidea olivacea) Small tree finch (Camarhynchus parvulus) Small tree finch (Camarhynchus parvulus) Medium ground finch (Geospizia fortis) Small ground finch (Geospizia fuliginosa) Small ground finch (Geospizia fuliginosa) Warbler finch (Certhidea olivacea) Small tree finch (Camarhynchus parvulus)
We tested the repellent effect of P. galapageium on the local mosquito fauna in a field experiment using 17 human subjects, each of whom treated one leg and one arm with crushed P. galapageium leaves and left the other arm and leg untreated
We assessed the response of the mosquito Anopheles arabiensis to blood-filled sausages treated with an ethanol extract of P. galapageium leaves compared to two controls, one treated with ethanol and the second with an extract of Rubus idaeus

Summary

Introduction

Species Warbler finch (Certhidea olivacea) Warbler finch (Certhidea olivacea) Warbler finch (Certhidea olivacea) Small tree finch (Camarhynchus parvulus) Small tree finch (Camarhynchus parvulus) Medium ground finch (Geospizia fortis) Small ground finch (Geospizia fuliginosa) Small ground finch (Geospizia fuliginosa) Warbler finch (Certhidea olivacea) Small tree finch (Camarhynchus parvulus). The only available blood source in such nests is the incubating female suggesting that they are being parasitized by P. downsi larvae Independent support for this comes from the finding that incubating female medium ground finches from parasitized nests showed higher P. downsi-specific antibody levels than females from parasite free nests[24]. Based on this knowledge about the negative effect of mosquitoes and P. downsi on Darwin’s finches we hypothesized that the behaviour of rubbing plants into feathers could have one or more possible effects: the plant extract might deter mosquitoes from biting; it might prevent adult P. downsi flies from entering the nest; it might protect incubating females from being bitten by P. downsi larvae or it might affect larval growth. In the light of these possible effects, we tested the repellent effect of P. galapageium on mosquitoes, on adult P. downsi flies and its effect on the growth of P. downsi larvae

Methods

Results

Conclusion