scholarly journals Natural and artificial scents do not increase egg rejection rates of model brood parasitic eggs by American robins (Turdus migratorius)

2020 ◽  
Vol 66 (4) ◽  
Author(s):  
Mark Erno Hauber
Keyword(s):  
Host Species ◽  
Molothrus Ater ◽  
Egg Rejection ◽  
Turdus Migratorius ◽  
Data Set ◽  
Brood Parasites ◽  
American Robins ◽  
Tactile Cues ◽  
Do So ◽  
Rejection Rates

Hosts of obligate avian brood parasites can diminish or eliminate the costs of parasitism by rejecting foreign eggs from the nests. A vast literature demonstrates that visual and/or tactile cues can be used to recognize and reject natural or model eggs from the nests of diverse host species. However, data on olfaction-based potential egg recognition cues are both sparse and equivocal: experimentally-applied, naturally-relevant (heterospecific, including parasitic) scents do not appear to increase egg rejection rates in two host species, whereas unnatural scents (human and tobacco scents) do so in one host species. Here I assessed the predictions that (i) human handling of mimetically-painted model eggs would increase rejection rates, and (ii) applying unnatural or natural scents to mimetically or non-mimetically painted model eggs alters these eggs’ respective rejection rates relative to controls. I studied wild American Robins (Turdus migratorius), a robust rejecter species of the eggs of obligate brood parasitic Brown-headed Cowbirds (Molothrus ater). There was no statistical evidence to support either prediction, whereas poorer color-mimicry was still a predicted cause of greater egg rejection in this data set. Nonetheless, future studies could focus on this and other host species and using these and different methods to apply and maintain the scenting of model eggs to more directly test hosts’ use of potential olfactory cues in the foreign-egg rejection process.

scholarly journals Mimicry-dependent lateralization in the visual inspection of foreign eggs by American robins

2019 ◽  
Vol 15 (7) ◽  
pp. 20190351 ◽  
Author(s):  
Hannah M. Scharf ◽  
Katharine Stenstrom ◽  
Miri Dainson ◽  
Thomas J. Benson ◽  
Esteban Fernandez-Juricic ◽  
...  
Keyword(s):  
Visual Processing ◽  
Species Recognition ◽  
Molothrus Ater ◽  
Population Level ◽  
Brain Lateralization ◽  
Turdus Migratorius ◽  
Brain Hemispheres ◽  
Brood Parasites ◽  
Visual Hemifield ◽  
American Robins

Brain lateralization, or the specialization of function in the left versus right brain hemispheres, has been found in a variety of lineages in contexts ranging from foraging to social and sexual behaviours, including the recognition of conspecific social partners. Here we studied whether the recognition and rejection of avian brood parasitic eggs, another context for species recognition, may also involve lateralized visual processing. We focused on American robins ( Turdus migratorius ), an egg-rejecter host to occasional brood parasitism by brown-headed cowbirds ( Molothrus ater ) and tested if robins preferentially used one visual hemifield over the other to inspect mimetic versus non-mimetic model eggs. At the population level, robins showed a significantly lateralized absolute eyedness index (EI) when viewing mimetic model eggs, but individuals varied in left versus right visual hemifield preference. By contrast, absolute EI was significantly lower when viewing non-mimetic eggs. We also found that robins with more lateralized eye usage rejected model eggs at higher rates. We suggest that the inspection and recognition of foreign eggs represent a specialized and lateralized context of species recognition in this and perhaps in other egg-rejecter hosts of brood parasites.

scholarly journals The costs of avian brood parasitism explain variation in egg rejection behaviour in hosts

2015 ◽  
Vol 11 (7) ◽  
pp. 20150296 ◽  
Author(s):  
Iliana Medina ◽  
Naomi E. Langmore
Keyword(s):  
Comparative Analysis ◽  
Host Species ◽  
Brood Parasitism ◽  
Large Scale ◽  
Bird Species ◽  
Egg Rejection ◽  
Brood Parasites ◽  
Avian Brood Parasitism ◽  
First Time ◽  
Rejection Rates

Many bird species can reject foreign eggs from their nests. This behaviour is thought to have evolved in response to brood parasites, birds that lay their eggs in the nest of other species. However, not all hosts of brood parasites evict parasitic eggs. In this study, we collate data from egg rejection experiments on 198 species, and perform comparative analyses to understand the conditions under which egg rejection evolves. We found evidence, we believe for the first time in a large-scale comparative analysis, that (i) non-current host species have rejection rates as high as current hosts, (ii) egg rejection is more likely to evolve when the parasite is relatively large compared with its host and (iii) egg rejection is more likely to evolve when the parasite chick evicts all the host eggs from the nest, such as in cuckoos. Our results suggest that the interactions between brood parasites and their hosts have driven the evolution of egg rejection and that variation in the costs inflicted by parasites is fundamental to explaining why only some host species evolve egg rejection.

scholarly journals Glucocorticoids mediate egg rejection in a brood parasite host

2019 ◽  
Author(s):  
Mikus Abolins-Abols ◽  
Mark E. Hauber
Keyword(s):  
Causal Link ◽  
Host Responses ◽  
Egg Rejection ◽  
Brood Parasite ◽  
Ecological Significance ◽  
Turdus Migratorius ◽  
Free Living ◽  
Brood Parasites ◽  
American Robins ◽  
Host Behaviour

AbstractAvian brood parasites and their hosts are engaged in a coevolutionary battle that can result in the evolution of sophisticated trickery by parasites and novel defence behaviours in hosts. Despite the clear evolutionary and ecological significance of host behaviour, however, we know very little about the mechanisms that regulate host defences, which limits our understanding of both inter- and intraspecific variation in host responses to parasitism. Here we tested whether corticosterone, a hormone known to be upregulated in hosts exposed to parasitism, also mediates one of the most frequent host defences – the rejection of foreign eggs. We experimentally reduced corticosterone levels in free-living brood parasite hosts, American robins Turdus migratorius, using mitotane and found that the likelihood of model egg rejection was significantly lower in the mitotane-treated birds relative to the sham-treated birds. These results demonstrate a causal link between glucocorticoids and egg rejection in hosts of avian brood parasites, but the physiological and sensory-cognitive pathways that regulate this effect remain unknown.

scholarly journals Visual acuity and egg spatial chromatic contrast predict egg rejection behavior of American robins

2020 ◽  
Vol 223 (20) ◽  
pp. jeb229609
Author(s):  
Alec B. Luro ◽  
Esteban Fernández-Juricic ◽  
Patrice Baumhardt ◽  
Mark E. Hauber
Keyword(s):  
Visual Acuity ◽  
Host Species ◽  
Spatial Vision ◽  
Viewing Distance ◽  
Egg Rejection ◽  
Chromatic Contrast ◽  
Brood Parasites ◽  
American Robins ◽  
Avian Visual System ◽  
The Cost

ABSTRACTColor and spatial vision is critical for recognition and discrimination tasks affecting fitness, including finding food and mates, and recognizing offspring. For example, as a counter defense to avoid the cost of raising the unrelated offspring of obligate interspecific avian brood parasites, many host species routinely view, recognize and remove the foreign egg(s) from their nests. Recent research has shown that host species visually attend to both chromatic and spatial pattern features of eggs; yet how hosts simultaneously integrate these features together when recognizing eggs remains an open question. Here, we tested egg rejection responses of American robins (Turdus migratorius) using a range of 3D-printed model eggs covered with blue and yellow checkered patterns differing in relative square sizes. We predicted that robins would reject a model egg if they could visually resolve the blue and yellow squares as separate features, or accept it if the squares blended together and appeared similar in color to the natural blue–green color of robin eggs as perceived by the avian visual system. As predicted, the probability of robins rejecting a model egg increased with greater sizes of its blue and yellow squares. Our results suggest that chromatic visual acuity and viewing distance have the potential to limit the ability of a bird to recognize a foreign egg in its nest, thus providing a limitation to host egg recognition that obligate interspecific avian brood parasites may exploit.

scholarly journals Visual acuity and egg spatial chromatic contrast predict egg rejection behavior of American robins

2020 ◽  
Author(s):  
Alec B. Luro ◽  
Esteban Fernández-Juricic ◽  
Patrice Baumhardt ◽  
Mark E. Hauber
Keyword(s):  
Visual Acuity ◽  
Host Species ◽  
Spatial Vision ◽  
Viewing Distance ◽  
Egg Rejection ◽  
Chromatic Contrast ◽  
Brood Parasites ◽  
American Robins ◽  
Avian Visual System ◽  
The Cost

AbstractColor and spatial vision are critical for recognition and discrimination tasks affecting fitness, including finding food and mates and recognizing offspring. For example, as a counter defense to avoid the cost of raising the unrelated offspring of obligate interspecific avian brood parasites, many host species routinely view, recognize, and remove the foreign egg(s) from their nests. Recent research has shown that host species visually attend to both chromatic and spatial pattern features of eggs; yet how hosts simultaneously integrate these features together when recognizing eggs remains an open question. Here, we tested egg rejection responses of American robins (Turdus migratorius) using a range of 3D-printed model eggs covered with blue and yellow checkered patterns differing in relative square sizes. We predicted that robins would reject a model egg if they could visually resolve the blue and yellow squares as separate features or accept it if the squares blended together and appeared similar in color to the natural blue-green color of robin eggs as perceived by the avian visual system. As predicted, the probability of robins rejecting a model egg increased with greater sizes of its blue and yellow squares. Our results suggest that chromatic visual acuity and viewing distance have the potential to limit the ability of a bird to recognize a foreign egg in its nest, thus providing a limitation to host egg recognition that obligate interspecific avian brood parasites may exploit.

Nest illumination and the evolution of egg rejection in hosts of brood parasites

The Auk ◽  
2019 ◽  
Vol 136 (1) ◽  
Author(s):  
Iliana Medina ◽  
Naomi E Langmore
Keyword(s):  
Host Species ◽  
Natural Light ◽  
Egg Rejection ◽  
Host Defenses ◽  
Brood Parasites ◽  
Light Levels ◽  
Main Host ◽  
Rapid Changes ◽  
High Rejection ◽  
Rejection Rates

ABSTRACT Hosts of avian brood parasites, such as cuckoos, are duped into taking care of a foreign chick and this has led to the evolution of host defenses, such as egg rejection. However, many host species are not egg rejecters and it has been suggested that poor illumination inside closed nests may constrain the evolution of this defense. In this study, we experimentally increased the light inside the dome nests of Yellow-Rumped Thornbills, the main host of the Shining Bronze-Cuckoo. Our results show that rejection events did not increase significantly when nests were brighter, although there is a possibility that rejection mistakes could decrease. Moreover, we found that natural light levels inside dome nests were highly variable, and in many cases as high as those in cup-nesting species with high rejection rates. This evidence suggests that rapid changes in nest illumination do not alter rejection behavior.

scholarly journals Did Blue Eggs of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) Cuckoos Evolve to Counter Host Discrimination?

The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 851-854
Author(s):  
Janice C. Lorenzana ◽  
Spencer G. Sealy
Keyword(s):  
Host Species ◽  
Observational Evidence ◽  
Host Discrimination ◽  
Turdus Migratorius ◽  
Egg Discrimination ◽  
American Robins ◽  
Dumetella Carolinensis ◽  
Egg Mimicry ◽  
Blue Coloration ◽  
Do So

Abstract Hughes (1997) hypothesized that the blue coloration of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoo eggs evolved in response to egg discrimination by their hosts. From that hypothesis, we predicted that cuckoo hosts would eject ancestral nonmimetic (white) eggs, but be more likely to accept mimetic (blue) eggs. American Robins (Turdus migratorius) and Gray Catbirds (Dumetella carolinensis) were used to test that hypothesis because they are ejecter species that lay blue eggs and have been parasitized by Coccyzus cuckoos. Hughes' egg-mimicry hypothesis was not supported because robins and catbirds did not significantly eject white cuckoo eggs more frequently than blue cuckoo eggs. Indeed, most robins accepted both egg types. Furthermore, the observational evidence for egg mimicry is not convincing because only 5 of the 15 host species that Hughes (1997) described as having eggs that “fully or nearly match” the egg color of Black-billed and Yellow-billed cuckoos actually do so.

scholarly journals Endocrine regulation of egg rejection in an avian brood parasite host

2020 ◽  
Vol 16 (6) ◽  
pp. 20200225 ◽  
Author(s):  
Mikus Abolins-Abols ◽  
Mark E. Hauber
Keyword(s):  
Stress Response ◽  
Stress Physiology ◽  
Endocrine Regulation ◽  
Egg Rejection ◽  
Brood Parasite ◽  
Potential Mechanism ◽  
Turdus Migratorius ◽  
American Robins ◽  
Defence Behaviour ◽  
Behavioural Adaptations

Parasite–host coevolution can lead to novel behavioural adaptations in hosts to resist parasitism. In avian obligate brood parasite and host systems, many host species have evolved diverse cognitive and behavioural traits to recognize and reject parasitic eggs. Our understanding of the evolution and ecology of these defences hinges on identifying the mechanisms that regulate them. We hypothesized that corticosterone, a hormone linked to stress response, vigilance and the suppression of parental behaviour, stimulates the rejection of foreign eggs by brood parasite hosts. We experimentally reduced circulating glucocorticoid levels with mitotane injections in American robins Turdus migratorius and found that the mitotane-treated birds rejected foreign eggs at a lower frequency compared to the sham-treated subjects. This is the first study to causally identify a potential mechanism of a widespread defence behaviour, and it is consistent with egg rejection being mediated by stress physiology.

Clutch variation and egg rejection in three hosts of the pallid cuckoo, Cuculus pallidus

Behaviour ◽  
2010 ◽  
Vol 147 (1) ◽  
pp. 19-36 ◽  
Author(s):  
Naomi Langmore ◽  
Michelle Landstrom ◽  
Robert Heinsohn
Keyword(s):  
Host Species ◽  
Rejection Rate ◽  
Objective Measures ◽  
Egg Rejection ◽  
Brood Parasite ◽  
Reflectance Spectrophotometry ◽  
Brood Parasites ◽  
Parasitised Host

AbstractIn theory, hosts of avian brood parasites would benefit by modifying their egg appearance in two ways to help identify mimetic foreign eggs: (i) by laying clutches that are more uniform in appearance and (ii) by laying clutches that differ from those of other females in the population. Support for these theories is inconsistent, and few studies have used objective measures of clutch variation. Here we used reflectance spectrophotometry to quantify within-clutch and between-clutch variation of three host species of an Australian brood parasite, the pallid cuckoo (Cuculus pallidus). We used egg-swapping experiments in which subjects were presented with either a conspecific egg or a heterospecific egg to compare the egg rejection responses of a frequently parasitised host, the white-plumed honeyeater (Lichenostomus penicillatus), with two less frequently parasitised hosts, dusky woodswallows (Artamus cyanopterus) and willie wagtails (Rhipidura leucophrys). As predicted, rejection rate increased as contrast between foreign egg and host clutch increased. Further, the major host showed greater between-clutch variation than the occasional hosts, and also rejected more similar-looking eggs. Contrary to predictions however, within-clutch variation was not lower in the major host, nor was it important in predicting the rejection rate of foreign eggs by the three host species.

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