Host response to cuckoo song is predicted by the future risk of brood parasitism

Sonia Kleindorfer,Diane Colombelli-Négrel,Christine Evans,Matteo Griggio,Herbert Hoi,Jeremy Robertson

doi:10.1186/1742-9994-10-30

Sonia Kleindorfer, Diane Colombelli-Négrel + Show 4 more

Open Access

https://doi.org/10.1186/1742-9994-10-30

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Abstract

IntroductionRisk assessment occurs over different temporal and spatial scales and is selected for when individuals show an adaptive response to a threat. Here, we test if birds respond to the threat of brood parasitism using the acoustical cues of brood parasites in the absence of visual stimuli. We broadcast the playback of song of three brood parasites (Chalcites cuckoo species) and a sympatric non-parasite (striated thornbill, Acanthiza lineata) in the territories of superb fairy-wrens (Malurus cyaneus) during the peak breeding period and opportunistic breeding period. The three cuckoo species differ in brood parasite prevalence and the probability of detection by the host, which we used to rank the risk of parasitism (high risk, moderate risk, low risk).ResultsHost birds showed the strongest response to the threat of cuckoo parasitism in accordance with the risk of parasitism. Resident wrens had many alarm calls and close and rapid approach to the playback speaker that was broadcasting song of the high risk brood parasite (Horsfield’s bronze-cuckoo, C. basalis) across the year (peak and opportunistic breeding period), some response to the moderate risk brood parasite (shining bronze-cuckoo, C. lucidus) during the peak breeding period, and the weakest response to the low risk brood parasite (little bronze-cuckoo, C. minutillus). Playback of the familiar control stimulus in wren territories evoked the least response.ConclusionHost response to the threat of cuckoo parasitism was assessed using vocal cues of the cuckoo and was predicted by the risk of future parasitism.

Highlights

Risk assessment occurs over different temporal and spatial scales and is selected for when individuals show an adaptive response to a threat
Host birds showed the strongest response to the threat of cuckoo parasitism in accordance with the risk of parasitism
We secondly aim to investigate whether investment into brood defence varies according to (1) the risk of brood parasitism, (2) the energetic cost of defence behaviour: we assume that alarm calls require less energy, and that approach to the threat requires more energy, and (3) the seasonal probability of parasitism risk, comparing the low risk period and high risk period

Summary

Introduction

Risk assessment occurs over different temporal and spatial scales and is selected for when individuals show an adaptive response to a threat. Throughout a lifetime, individuals are faced with a variety of threats, including infectious disease, adverse weather conditions, limited food availability, predation and brood parasitism. Selection should favour cues that facilitate the recognition of a costly interaction, including the degree of risk of the interaction [5]. These cues may come directly from the threat, such as the vocalisation of a predator or the sight of a brood parasite [6,7]. The risk of a threat may change during an encounter and risk assessment should be dynamic, whereby individuals modify their response according to perceived risk as proposed by Curio and colleagues [2] and amply tested in host-parasite systems [2,15,16]

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