Pattern recognition algorithm reveals how birds evolve individual egg pattern signatures

Stoddard, Mary Caswell; Kilner, Rebecca M.; Town, Christopher

doi:10.1038/ncomms5117

Cited by 143 publications

(142 citation statements)

References 46 publications

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“…This then selects for increasingly fine-tuned discrimination by hosts (Davies and Brooke, 1989;Stevens, 2010, 2011;Davies, 2011). Such an arms-race is a canonical example of co-evolutionary processes driving both perceptual and signaling mechanisms (Davies and Brooke, 1989;Davies, 2011;Igic et al, 2012;Stoddard et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…While above-threshold visual contrast is increasingly known to induce egg rejection among brood parasite hosts, it is not firmly established whether comparing own versus foreign eggs is a more reliable cue than other visual comparisons available in the host's nest environment (Endler and Mielke, 2005;Thorogood and Davies, 2013). For example, relatively few studies have examined whether and how nest lining color influences parental behavior (but see Bailey et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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The role of egg-nest contrast in the rejection of brood parasitic eggs

Aidala

Croston

Schwartz

et al. 2015

Journal of Experimental Biology

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Hosts of avian brood parasites can avoid the reproductive costs of raising genetically unrelated offspring by rejecting parasitic eggs. The perceptual cues and controls mediating parasitic egg discrimination and ejection are well studied: hosts are thought to use differences in egg color, brightness, maculation, size and shape to discriminate between their own and foreign eggs. Most theories of brood parasitism implicitly assume that the primary criteria to which hosts attend when discriminating eggs are differences between the eggs themselves. However, this assumption is confounded by the degree to which chromatic and achromatic characteristics of the nest lining co-vary with egg coloration, so that egg-nest contrast per se might be the recognition cue driving parasitic egg detection. Here, we systematically tested whether and how egg-nest contrast itself contributes to foreign egg discrimination. In an artificial parasitism experiment, we independently manipulated egg color and nest lining color of the egg-ejector American robin (Turdus migratorius), a host of the obligate brood parasitic brown-headed cowbird (Molothrus ater). We hypothesized that the degree of contrast between foreign eggs and the nest background would affect host egg rejection behavior. We predicted that experimentally decreasing egg-nest chromatic and achromatic contrast (i.e. rendering parasitic eggs more cryptic against the nest lining) would decrease rejection rates, while increasing egg-nest contrast would increase rejection rates. In contrast to our predictions, egg-nest contrast was not a significant predictor of egg ejection patterns. Instead, egg color significantly predicted responses to parasitism. We conclude that eggegg differences are the primary drivers of egg rejection in this system. Future studies should test for the effects of egg-nest contrast per se in predicting parasitic egg recognition in other host-parasite systems, including those hosts building enclosed nests and those parasites laying cryptic eggs, as an alternative to hypothesized effects of egg-egg contrast.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The role of egg-nest contrast in the rejection of brood parasitic eggs

Aidala

Croston

Schwartz

et al. 2015

Journal of Experimental Biology

View full text Add to dashboard Cite

show abstract

“…However, background color is not the only feature used in recognition, because coots reject many eggs that do not differ measurably in background color from the host's eggs. There is increasing evidence that spotting patterns may also be more important than background color in hosts of mimetic interspecific parasitic eggs (Lahti & Lahti, 2002;Stoddard, Kilner, & Town, 2014). The use of spots for egg recognition in coots could explain the seemingly paradoxical results of our mimicry experiment, whereby hosts treated all three treatments similarly despite the treatments representing a gradient of similarity in shape and background colour (Lyon & Eadie, 2004).…”

Section: Discussionmentioning

confidence: 87%

Interspecific egg rejection as ecological collateral damage from selection driven by conspecific brood parasitism

2015

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“…These studies assess chromatic reflectance and/or pattern data to characterize how the tetrachromatic avian visual system assesses the foreign eggshell's appearance (Avilés et al 2010 ;Stoddard and Stevens 2011 ;Hanley et al 2013 ;Igic et al 2012 ;Poláček et al 2013 ;Stoddard et al 2014 ), and have repeatedly confirmed long-standing conclusions that foreign eggs are rejected more often when they are perceived as more dissimilar to the hosts' own eggs (Cassey et al 2008 ;Spottiswoode and Stevens 2010 ;Stevens et al 2013 ;Croston and Hauber 2014 ;Hauber et al 2015 ; Fig. 1 ).…”

Section: Aq4mentioning

confidence: 98%

Experimental shifts in egg–nest contrasts do not alter egg rejection responses in an avian host–brood parasite system

et al. 2015

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Obligate brood parasitic birds exploit their hosts to provide care for unrelated young in the nest. Potential hosts can reduce the cost of parasitism by rejecting foreign eggs from the nest. Observational, comparative, and experimental studies have concluded that most hosts use the coloration and patterning of eggshells to discriminate between own and foreign eggs in the nest. However, an alternative hypothesis is that birds use the colour contrasts between eggshells and the nest lining to identify parasitic eggs (egg-nest contrast hypothesis). In support of this hypothesis, we found that the avian perceivable chromatic contrasts between dyed eggs and unmanipulated nest linings significantly and negatively covaried with the rejection rates of different dyed eggs of the great reed warbler Acrocephalus arundinaceus, a frequently parasitized host of the common cuckoo Cuculus canorus. To experimentally test whether egg-nest contrasts influence rejection, we reciprocally dyed both eggs and the nest lining of this host species with one of two colours: orange and green. Contrary to the egg-nest contrast hypothesis, host rejection patterns in response to dyed eggs were not altered by dyeing nests, relative to unmanipulated control eggs and nests. In turn, experimental egg colour was the only significant predictor of egg rejection rate. Our results demonstrate that egg-nest contrast is a collateral, not a causal factor in egg rejection, and confirm the conclusions of previous studies that hosts can rely on the parasitic egg's appearance itself to recognize the foreign egg in the nest.

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Pattern recognition algorithm reveals how birds evolve individual egg pattern signatures

Cited by 143 publications

References 46 publications

The role of egg-nest contrast in the rejection of brood parasitic eggs

The role of egg-nest contrast in the rejection of brood parasitic eggs

Interspecific egg rejection as ecological collateral damage from selection driven by conspecific brood parasitism

Experimental shifts in egg–nest contrasts do not alter egg rejection responses in an avian host–brood parasite system

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