Common cuckoo females remove more conspicuous eggs during parasitism

Longwu Wang,Yuhan Zhang,Anders Pape Møller,Wei Liang

doi:10.1098/rsos.201264

Abstract

Avian obligate brood parasites gain an advantage by removing the eggs of the cuckoos who have already visited the nest, which can increase the chances of survival for their offspring. Conversely, to prevent their eggs from being picked up by the next parasitic cuckoo, they need to take some precautions. Egg mimicry and egg crypsis are two alternative strategies to prevent the parasitized egg from being picked up by another parasitic cuckoo. Here, we tested whether the egg crypsis hypothesis has a preventative effect when common cuckoos (Cuculus canorus) parasitize their Oriental reed warbler (Acrocephalus orientalis) hosts. We designed two experimental groups with different crypsis effects to induce common cuckoos to lay eggs and observed whether the cuckoos selectively picked up the experimental eggs with low crypsis levels in the process of parasitism. Our results supported the egg crypsis hypothesis; the observed cuckoos significantly preferred to select the more obvious white model eggs. This shows that even in an open nest, eggs that are adequately hidden can also be protected from being picked up by cuckoo females during parasitism so as to increase the survival chance of their own parasitic eggs.

Highlights

Parasites, such as cuckoos and cowbirds, lay their eggs in the nests of other birds; passing the high reproductive cost of royalsocietypublishing.org/journal/rsos R
The main finding of this study was that common cuckoo females preferred to pick up the white model eggs with high brightness, regardless of whether those eggs were in the black or white painted nests
From group 1, our results supported the egg crypsis hypothesis that the more conspicuous the egg, the more likely it is to be removed by common cuckoos

Summary

Introduction

Parasites, such as cuckoos and cowbirds, lay their eggs in the nests of other birds; passing the high reproductive cost of royalsocietypublishing.org/journal/rsos R. Parental care on to their hosts [1,2]. This causes selection for the evolution of anti-parasite strategies such 2 as nest defence and egg recognition [3,4,5]. An adaptive parasite has to choose the right time to quickly lay its eggs and escape the crime scene, avoiding an attack from the host or reducing the suspicion and detection of the eggs by the host [6,7,8]. In addition to laying eggs in such a limited time (3–10 s) [7,8], the parasite usually removes one or two eggs from the host’s nest [9,10,11]

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