For the infection experiment, we caught wild birds at the end of the breeding season in June and July and selected adult males to minimize variation owing to sex or age. All individuals were evaluated for infection, with those testing negative quarantined for at least one week before confirming infection status. These birds were then kept in vector-protected aviaries furnished with cut reeds, several feeders and water ad libitum. The aviaries allowed free ranging between an indoor (1.3–2.6 × 2.3 × 2.5 m) and an outdoor section (size: 1.5–2.5 × 1.1 × 2.4 m).