A Meta-Analysis of Avian Egg Traits Cueing Egg-Rejection Defenses Against Brood Parasitism

Samaš, Peter; Hauber, Márk E.; Honza, Marcel

doi:10.3389/fevo.2021.703208

Cited by 22 publications

(15 citation statements)

References 75 publications

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“…In a recent and large‐scale meta‐analysis conducted across all hosts and brood parasites (Samaš et al, 2021), eggshell color was the most frequently investigated trait in obligate brood parasitism experiments. Since model cuckoo eggs painted to be mimetic or nonmimetic to blackbird eggs were frequently used in experimenting with Eurasian blackbird populations, and blackbird eggs are larger than cuckoo eggs (Moskát et al, 2003), many of the tests in blackbirds tested both color and size (see below, 3.1.1.3).…”

Section: Resultsmentioning

confidence: 99%

A review of the cues used for rejecting foreign eggs from the nest by the Eurasian blackbird (Turdus merula)

Fulmer

Hauber

2022

Ecology and Evolution

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Avian brood parasitism is reproductively costly for hosts and selects for cognitive features enabling anti-parasitic resistance at multiple stages of the host's breeding cycle. The true thrushes (genus Turdus) represent a nearly worldwide clade of potential hosts of brood parasitism by Cuculus cuckoos in Eurasia and Africa and Molothrus cowbirds in the Americas. The Eurasian blackbird (Turdus merula) builds an open-cup nest and is common within much of the common cuckoo's (C. canorus) breeding range.While this thrush is known to be parasitized at most only at low rates by this cuckoo, the species is also a strong rejector of nonmimetic foreign eggs in the nest. Given their open-cup nesting habits, we predict that Eurasian blackbirds primarily use visual cues in making a distinction between own and parasitically or experimentally inserted foreign eggs in the nest. We then provide a comprehensive and quantitative review of the literature on blackbird egg rejection studies. This review corroborates that vision is the primary sensory modality used by blackbirds in assessing eggs, but also brings attention to some other, less commonly studied cues which appear to influence rejection, including predator exposure, individual experience, stage of clutch completion, and maternal hormonal state. Blackbirds are also able to recognize and eject even highly mimetic eggs (including those of conspecifics) at a moderate rate, apparently relying on many of the same sensory cues. Although the cues involved in foreign egg recognition by Eurasian blackbirds do not appear specialized to nonmimetic cuckoo parasitism, we cannot differentiate between the possibility of egg rejection being selected by mostly conspecific parasitism or by the evolutionary ghost of a now-extinct, mimetic cuckoo host-race.

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Section: Resultsmentioning

confidence: 99%

A review of the cues used for rejecting foreign eggs from the nest by the Eurasian blackbird (Turdus merula)

Fulmer

Hauber

2022

Ecology and Evolution

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“…Once laid, eggs are typically protected and incubated in nests until they successfully hatch. There are three major exceptions to this pattern: (i) the rejection of brood-parasitic eggs from the nests of many host species [ 1 – 3 ], (ii) the pecking and destruction or the removal of eggs by some brood parasites in hosts' nests [ 4 , 5 ], and (iii) the predation and consumption of eggs ([ 6 ]; not the subject of this study).…”

Section: Introductionmentioning

confidence: 99%

Gradual changes in model shape affect egg-directed behaviours by parasitic shiny cowbirds Molothrus bonariensis in captivity

et al. 2023

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Eggs are critically important for avian reproduction as all birds are oviparous. Accordingly, the recognition and care of own eggs represent the cornerstones of avian breeding, whereas the elimination of foreign objects, including brood-parasitic eggs and non-egg items from the nest are known to also increase fitness by refocusing incubation effort on the parents' own eggs. But egg recognition also plays a role in some avian obligate brood parasites' reproductive strategy through the pecking of already present eggs in the hosts' clutch to reduce nestmate competition with the parasite's own hatchling. Here we tested egg shape recognition in this parasitic egg-pecking context by exposing two different series of 3D printed models to captive obligate brood-parasitic shiny cowbirds ( Molothrus bonariensis ) in artificial nests. Natural egg-shaped models were pecked more often compared with increasingly thinner models, but there was no effect of increasing angularity on pecking rates, implying that a natural, rather than an artificial, range of variability elicited adaptive responses from parasitic cowbirds.

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“…In their study, Honza et al (2014) found that cuckoos from this population selectively targeted hosts that laid eggs perceptually similar to their own. Studies such as this provide a powerful dataset to test hypotheses that depend on the egg phenotypes of both hosts and parasites, and how co-evolutionary dynamics may be shaping the evolutionary trajectories of both parties [23]. Due to prior work finding color-biased egg rejection in this species [15], we predict that hosts selection for bluer cuckoo eggs would result in reciprocal negative frequency-dependence, such that hosts should have bluer eggs than their parasite.…”

Section: Introductionmentioning

confidence: 99%

Consistent differences in eggshell phenotypes select for bluer eggs in an avian host-parasite system

Villa

Wisocki²,

Cruz

et al. 2022

Preprint

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Avian brood parasitism is a well-recognized model for studying coevolution. In this model, hosts adapt the ability to recognize and remove parasitic young to avoid the costs of rearing foreign offspring, while parasites counter-adapt phenotypes to evade detection. A classic example of host-parasite coevolutionary arms race is the great reed warbler and its parasite the common cuckoo (hereafter "warbler" and "cuckoo", respectively). Recent work has found that cuckoo eggs are more likely to be accepted by warblers when those are bluer than their own eggs. Therefore, hosts would select for bluer cuckoo eggs; in turn, this provides directional selection for hosts eggs to remain bluer than cuckoo eggs. Here, we tested whether there were consistent differences in eggshell appearance between cuckoo and warbler eggs using a dataset which provides eggshell coloration of both warblers and cuckoos from the same nest. Despite being a textbook example of mimicry, we found that the cuckoos have significantly browner eggs than the warblers. These findings most likely suggest that this warbler-cuckoo system is experiencing negative frequency-dependent selection, as expected under red queen dynamics. Future research comparing warbler-cuckoo interactions over time would advance our understanding of the coevolution between avian brood parasites and their hosts.

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A Meta-Analysis of Avian Egg Traits Cueing Egg-Rejection Defenses Against Brood Parasitism

Cited by 22 publications

References 75 publications

A review of the cues used for rejecting foreign eggs from the nest by the Eurasian blackbird (Turdus merula)

A review of the cues used for rejecting foreign eggs from the nest by the Eurasian blackbird (Turdus merula)

Gradual changes in model shape affect egg-directed behaviours by parasitic shiny cowbirds Molothrus bonariensis in captivity

Consistent differences in eggshell phenotypes select for bluer eggs in an avian host-parasite system

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