From dispenser to nest: collection of fumigated material repels parasites across behavioural traits in Darwin's finches.

In the midst of a biodiversity crisis, it is important to conserve diversity at all levels, including species, genetic, and behavioural diversity. Animals with different behavioural traits can interact with their environment in distinct ways; hence, the distribution of behavioural traits within a population can influence the efficacy and outcome of conservation interventions. On the Galápagos Islands, Darwin’s finches are threatened by an invasive parasite, the avian vampire fly, Philornis downsi. Avian vampire fly larvae develop in the base of the nest, where they feed on the blood and tissue of developing nestlings, causing high mortality. In this study on Floreana Island, we deployed dispensers filled with insecticide-treated nesting material, a conservation method that has been found to decrease parasite load and increase fledging success. We then assessed whether individual differences in Darwin’s finch neophilia (response to a novel object) and aggressiveness (response to a simulated territory intrusion) affected their use of treated material. We found that ~57% of nests contained treated nesting material and that increasing volumes of treated material were associated with decreased parasite load. We found no effect of neophilia or aggressiveness on the probability of using treated material or amount of treated material used. Our results support nesting material dispensers as an effective conservation measure that conserves the full range of behavioural responses. To increase the efficacy of this method, future research should consider species- and individual-level preferences for material type and dispenser location.