Item

Abstract

The fitness effects of parasites on their hosts are often unknown. For most avian viruses, no records of clinical disease have been associated with infections. In this study we tested if birds would alter their behaviour during an infection with an avian virus that naturally occurs in passerines. We measured spontaneous locomotion activity and take-off performance of Common Greenfinches Carduelis chloris at the peak of infection with the Sindbis virus (Togaviridae, Alphavirus). We found that virus-treated birds had lower locomotion activity than saline-treated birds the third day after the injection. When exposed to a simulated predator attack, virus-treated birds reduced their take-off speed from before to after treatment, whereas saline-treated birds did the opposite. This difference between treatments in change in flight speed from before to after treatment was only detected in the evenings, when the birds were heavy. Furthermore, virus-treated birds increased in body mass from before to after treatment, whereas saline-treated birds did the opposite. Our results suggest that the infection with Sindbis virus is accompanied by energetic or pathological costs, and that infected birds accounted for these cost by reducing locomotion activity while increasing their energy intake. Down-regulating important behaviours such as take-off flight speed may have implications for the chances of survival of infected birds.