Snake-like hissing calls made by nestlings of the open nesting zitting cisticola <i>Cisticola juncidis</i>

Mimicry is widespread in the animal kingdom, with sound/or acoustic mimicry remaining less studied than visual mimicry. Some incubating female birds in cavity nests emit a hissing call when encountering nest predators, which sounds like a snake hiss and serves to scare off predators; this is considered a form of acoustic Batesian mimicry. Similarly, for nearly defenseless bird nestlings, using a hissing call to scare off predators can improve their survival; however, few studies have reported nestlings making hissing calls. In this study, we report on the hissing calls of nestlings of the open-nesting zitting cisticola <i>(Cisticola juncidis)</i> and compare their hissing calls with those of other animals, such as birds and snakes. The results showed that the hissing calls of <i>C. juncidis</i> nestlings closely approximate the sounds of snakes. This study is the first report of sounds that mimic snakes made by the nestlings of any open-nesting passerine bird species.