Female Cuckoo Calls Deceive Their Hosts by Evoking Nest-Leaving Behavior: Variation under Different Levels of Parasitism

Abstract

The common cuckoo (Cuculus canorus) is an obligate brood parasite that has evolved a series of strategies to trick its hosts. The female cuckoo has been hypothesized to mimic the appearance and sounds of several raptors to deceive the hosts into exhibiting anti-predator behavior. Such behavior would relax the protection of the host nest and thus allow the female cuckoo to approach the host nest unopposed. Many anti-parasite strategies have been found to vary among geographical populations due to different parasitic pressures from cuckoos. However, the effect of female cuckoo calls related to different levels of parasitic pressure has not been examined. Here, we studied the effect of female cuckoo calls on the oriental reed warbler (Acrocephalus orientalis), one of the major hosts of the common cuckoo, in two geographical populations experiencing different levels of parasite pressure. Four kinds of sounds were played back to the hosts: the calls from female common cuckoos, male common cuckoos, sparrowhawks (Accipiter nisus), and oriental turtle doves (Streptopelia orientalis). The results showed that the female cuckoo calls induced the hosts to leave their nests more frequently than the male cuckoo or dove calls in both populations, and two populations of the hosts reacted similarly to the female cuckoo calls, implying that the function of female cuckoo calls would not be affected by the difference in parasitism rate. This study indicates that female cuckoo calls function to distract the hosts’ attention from protecting their nests. However, we propose that such a deception by the female cuckoo call may not be due to the mimicry of sparrowhawk calls, but rather that the rapid cadence of the call that causes a sense of anxiety in the hosts.

Three sympatric host nestlings eavesdrop on cuckoo nestling distress calls

“…However, nestlings are not entirely unresponsive in the face of danger; they adopt certain behaviors to deter predators. Previous studies have determined that nestlings can obtain information regarding current risks from various sources, including predators (Haff & Magrath, 2010 ), parents (Jiang, Han, & Yang, 2022 ; Madden et al., 2005b ; Wang et al., 2022b ), and other prey species (Jiang, Han, Zhang, et al., 2022 ), and reduce their activity to hide themselves. For example, nestlings can both recognize different types of alarm calls made by their parents (Magrath et al., 2006 ; Platzen & Magrath, 2005 ; Suzuki, 2011 ) as well as independently assess predator cues, leading to silent responses (Haff & Magrath, 2010 ).…”