Rollers smell the fear of nestlings.

Many animals react to danger by producing chemical cues that can be smelled by others, which is called the smell of fear. Some bird species produce chemical compounds when threatened, such as nestlings of the Eurasian roller Coracias garrulus that vomit an odorous orange liquid when scared in their nests. Here, we experimentally explore the possibility that parents were informed about recent predation attempts at their nests through the olfaction of this vomit. Parents of nests treated with nestling vomit delayed their entrance to nests and decreased their provisioning rate in comparison with parents of nests treated with an odorous control. These results demonstrate that adult rollers are able to smell the fear of offspring and show for the first time in birds that a scent produced during an interspecific challenge has a role in an intraspecific communication scenario.