Risk-taking behavior relates to Leucocytozoon spp. infection in a sub-Antarctic rainforest bird

Parasites inhabit practically all environments of the planet, representing an important selective pressure on different traits, including behavior. However, there is limited knowledge on the relationship between haemosporidian infection and the behavior of birds. In this study, we recorded risk-taking behaviors exhibited during three behavioral tests: struggle in the hand, open-field, and simulated territorial intrusion, in a resident population of thorn-tailed Rayadito (Aphrastura spinicauda) located on Navarino Island (55°S), southern Chile. This population shows a high prevalence of the haemosporidian Leucocytozoon spp., providing us with an opportunity to explore the connection between this parasite and the risk-taking behaviors of a Neotropical bird species. Our results indicate that birds infected by Leucocytozoon spp. exhibit higher activity scores in the behavioral tests, suggesting that individuals infected may be more propensity for risky behaviors. These findings raise intriguing questions about whether behavior precedes infection or results from it.