Asian koel rapidly locates host breeding in novel nest sites.

Avian brood parasites depend upon locating host nests to lay their eggs. However, how brood parasites locate host nests and select the nests for parasitism remains poorly studied. Here, we examined how a non-evicting brood parasite, the Asian koel ( Eudynamys scolopaceus ) were able to locate host nests in locally novel nest sites. We provided a set of novel nest sites (i.e., nestboxes, n  = 100) to the common myna ( Acridotheres tristis ), a regular host of the Asian koel, at a field site in Central Bangladesh. We found that common myna quickly utilized the novel breeding sites ( n  = 99 nests across 59 boxes) and similarly, 21.2% of these nests were parasitized by the Asian koel. Unsurprisingly, none of the inactive nest boxes were parasitized, neither were empty nests of common myna (i.e., either predated or fledged clutches, thus lack of parental activity, n  = 83). Our results provide an experimental demonstration of the Asian koel ability to rapidly locate nests in locally novel nest sites, potentially facilitated by close monitoring of host activity and behavior around the nest site. However, the underlying mechanisms for this rapid adjustment to novel nest sites remain unresolved.