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Alex Kacelnik - One of the best experts on this subject based on the ideXlab platform.
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the wages of violence mobbing by Mockingbirds as a frontline defence against brood parasitic cowbirds
Animal Behaviour, 2013Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:For many hosts of brood-parasitic birds, their frontline of defence is to mob adult parasites that approach the nest. Mobbing is commonly interpreted as an adaptation to prevent the parasite from laying, although to date evidence of this is indirect or anecdotal. We investigated the effectiveness of mobbing by chalk-browed Mockingbirds, Mimus saturninus , as a defence against their parasite, the shiny cowbird, Molothrus bonariensis , using videos of 480 naturally occurring cowbird nest visits and other direct observations. Mockingbirds only occasionally prevented cowbirds from reaching the nest or from laying once in it. More often, cowbirds were able to deposit an egg, aided by their agile flight, rapid laying, endurance of mobbing and, in some cases, opportunistic timing, whereby they approached nests when Mockingbirds were distracted in battle with other cowbirds. Adult parasites present a second threat to hosts, however, in that they try to damage or remove host eggs prior to laying their own. We found that mobbing at the nest significantly reduced the likelihood that cowbirds broke a Mockingbird egg during their visit, despite almost all mobbed visits concluding with a cowbird laying an egg. In this host therefore, the benefit of mobbing must be assessed by two independent measures: prevention of egg laying by the parasite and loss of their own eggs. As Mockingbird eggs that survive a cowbird's visit intact can go on to fledge from parasitized broods, we expect strong selection for mobbing as an antiparasite defence in this host, even though it largely fails to prevent parasitism itself.
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brood parasite eggs enhance egg survivorship in a multiply parasitized host
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:Despite the costs to avian parents of rearing brood parasitic offspring, many species do not reject foreign eggs from their nests. We show that where multiple parasitism occurs, rejection itself can be costly, by increasing the risk of host egg loss during subsequent parasite attacks. Chalk-browed Mockingbirds (Mimus saturninus) are heavily parasitized by shiny cowbirds (Molothrus bonariensis), which also puncture eggs in host nests. Mockingbirds struggle to prevent cowbirds puncturing and laying, but seldom remove cowbird eggs once laid. We filmed cowbird visits to nests with manipulated clutch compositions and found that Mockingbird eggs were more likely to escape puncture the more cowbird eggs accompanied them in the clutch. A Monte Carlo simulation of this 'dilution effect', comparing virtual hosts that systematically either reject or accept parasite eggs, shows that acceptors enjoy higher egg survivorship than rejecters in host populations where multiple parasitism occurs. For Mockingbirds or other hosts in which host nestlings fare well in parasitized broods, this benefit might be sufficient to offset the fitness cost of rearing parasite chicks, making egg acceptance evolutionarily stable. Thus, counterintuitively, high intensities of parasitism might decrease or even reverse selection pressure for host defence via egg rejection.
Juan C Reboreda - One of the best experts on this subject based on the ideXlab platform.
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the wages of violence mobbing by Mockingbirds as a frontline defence against brood parasitic cowbirds
Animal Behaviour, 2013Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:For many hosts of brood-parasitic birds, their frontline of defence is to mob adult parasites that approach the nest. Mobbing is commonly interpreted as an adaptation to prevent the parasite from laying, although to date evidence of this is indirect or anecdotal. We investigated the effectiveness of mobbing by chalk-browed Mockingbirds, Mimus saturninus , as a defence against their parasite, the shiny cowbird, Molothrus bonariensis , using videos of 480 naturally occurring cowbird nest visits and other direct observations. Mockingbirds only occasionally prevented cowbirds from reaching the nest or from laying once in it. More often, cowbirds were able to deposit an egg, aided by their agile flight, rapid laying, endurance of mobbing and, in some cases, opportunistic timing, whereby they approached nests when Mockingbirds were distracted in battle with other cowbirds. Adult parasites present a second threat to hosts, however, in that they try to damage or remove host eggs prior to laying their own. We found that mobbing at the nest significantly reduced the likelihood that cowbirds broke a Mockingbird egg during their visit, despite almost all mobbed visits concluding with a cowbird laying an egg. In this host therefore, the benefit of mobbing must be assessed by two independent measures: prevention of egg laying by the parasite and loss of their own eggs. As Mockingbird eggs that survive a cowbird's visit intact can go on to fledge from parasitized broods, we expect strong selection for mobbing as an antiparasite defence in this host, even though it largely fails to prevent parasitism itself.
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different recognition cues reveal the decision rules used for egg rejection by hosts of a variably mimetic avian brood parasite
Animal Cognition, 2012Co-Authors: Alicia M De La Colina, Juan C Reboreda, Lorena Pompilio, Mark E Hauber, Bettina MahlerAbstract:Brood parasitism imposes several fitness costs on the host species. To reduce these costs, hosts of avian brood parasites have evolved various defenses, of which egg rejection is the most prevalent. In the face of variable host-parasite mimicry and the costs of egg discrimination itself, many hosts reject only some foreign eggs. Here, we experimentally varied the recognition cues to study the underlying cognitive mechanisms used by the Chalk-browed Mockingbird (Mimus saturninus) to reject the white immaculate eggs laid by the parasitic Shiny Cowbird (Molothrus bonariensis). Immaculate eggs are the only parasite eggs rejected by this host, as it accepts all polymorphic, spotted eggs laid by cowbirds. Using a within-breeding pair experimental design, we tested for the salience of spotting, UV reflectance, and brightness in eliciting rejection. We found that the presence of spotting significantly decreased the probability of rejection while increments in brightness significantly increased rejection frequencies. The cognitive rules underlying Mockingbird rejection behavior can be explained by a decision-making model which predicts changes in the levels of rejection in direct relation to the number of relevant attributes shared between host and parasite eggs.
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brood parasite eggs enhance egg survivorship in a multiply parasitized host
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:Despite the costs to avian parents of rearing brood parasitic offspring, many species do not reject foreign eggs from their nests. We show that where multiple parasitism occurs, rejection itself can be costly, by increasing the risk of host egg loss during subsequent parasite attacks. Chalk-browed Mockingbirds (Mimus saturninus) are heavily parasitized by shiny cowbirds (Molothrus bonariensis), which also puncture eggs in host nests. Mockingbirds struggle to prevent cowbirds puncturing and laying, but seldom remove cowbird eggs once laid. We filmed cowbird visits to nests with manipulated clutch compositions and found that Mockingbird eggs were more likely to escape puncture the more cowbird eggs accompanied them in the clutch. A Monte Carlo simulation of this 'dilution effect', comparing virtual hosts that systematically either reject or accept parasite eggs, shows that acceptors enjoy higher egg survivorship than rejecters in host populations where multiple parasitism occurs. For Mockingbirds or other hosts in which host nestlings fare well in parasitized broods, this benefit might be sufficient to offset the fitness cost of rearing parasite chicks, making egg acceptance evolutionarily stable. Thus, counterintuitively, high intensities of parasitism might decrease or even reverse selection pressure for host defence via egg rejection.
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early infestation by bot flies philornis seguyi decreases chick survival and nesting success in chalk browed Mockingbirds mimus saturninus
The Auk, 2007Co-Authors: Fabian L Rabuffetti, Juan C ReboredaAbstract:Abstract Bot flies (Diptera: Muscidae: Philornis spp.) are a group of flies comprising mostly species with a Neotropical distribution. Their larvae parasitize several species of birds, living subcutaneously on altricial chicks. We investigated the effect of parasitism by bot flies (P. seguyi) on the reproductive success of Chalk-browed Mockingbirds (Mimus saturninus) in temperate grasslands near the southern limit of bot fly distributions. We analyzed seasonal variation of bot fly prevalence during three consecutive years and how the timing and intensity of bot fly infestation affected growth and survival of Chalk-browed Mockingbird nestlings. Bot fly prevalence was 58.3%, 30.7%, and 45.5% each year, and in all years, it increased with time of breeding. Most of the infested nests fledged no chicks. In these nests, chicks had a lower tarsus growth rate than in noninfested nests and died 3–4 days after parasitism. The average time from hatching of the first chick until infestation was 4.4 days. The age of t...
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a comparative study of shiny cowbird parasitism of two large hosts the chalk browed Mockingbird and the rufous bellied thrush
The Condor, 2003Co-Authors: Paula Sackmann, Juan C ReboredaAbstract:Abstract It is usually accepted that generalist brood parasites should avoid using hosts larger than themselves because host chicks may outcompete parasite chicks for food. We studied the interactions between the Shiny Cowbird (Molothrus bonariensis) and two common hosts larger than the parasite, the Chalk-browed Mockingbird (Mimus saturninus) and the Rufous-bellied Thrush (Turdus rufiventris). For each host we determined (1) frequency and intensity of parasitism during the breeding season, (2) nesting success, egg survival, hatching success, and chick survival in unparasitized and parasitized nests, and (3) antiparasitic defenses. We also determined Shiny Cowbird egg survival, hatching success, and chick survival in both hosts. Parasitism reached 50% in Mockingbirds and 66% in thrushes. In both species the main cost of parasitism was egg destruction through punctures. Hatching success, survival of host chicks, and nest survival did not differ between unparasitized and parasitized nests. Both hosts reject...
Ros Gloag - One of the best experts on this subject based on the ideXlab platform.
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the wages of violence mobbing by Mockingbirds as a frontline defence against brood parasitic cowbirds
Animal Behaviour, 2013Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:For many hosts of brood-parasitic birds, their frontline of defence is to mob adult parasites that approach the nest. Mobbing is commonly interpreted as an adaptation to prevent the parasite from laying, although to date evidence of this is indirect or anecdotal. We investigated the effectiveness of mobbing by chalk-browed Mockingbirds, Mimus saturninus , as a defence against their parasite, the shiny cowbird, Molothrus bonariensis , using videos of 480 naturally occurring cowbird nest visits and other direct observations. Mockingbirds only occasionally prevented cowbirds from reaching the nest or from laying once in it. More often, cowbirds were able to deposit an egg, aided by their agile flight, rapid laying, endurance of mobbing and, in some cases, opportunistic timing, whereby they approached nests when Mockingbirds were distracted in battle with other cowbirds. Adult parasites present a second threat to hosts, however, in that they try to damage or remove host eggs prior to laying their own. We found that mobbing at the nest significantly reduced the likelihood that cowbirds broke a Mockingbird egg during their visit, despite almost all mobbed visits concluding with a cowbird laying an egg. In this host therefore, the benefit of mobbing must be assessed by two independent measures: prevention of egg laying by the parasite and loss of their own eggs. As Mockingbird eggs that survive a cowbird's visit intact can go on to fledge from parasitized broods, we expect strong selection for mobbing as an antiparasite defence in this host, even though it largely fails to prevent parasitism itself.
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brood parasite eggs enhance egg survivorship in a multiply parasitized host
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:Despite the costs to avian parents of rearing brood parasitic offspring, many species do not reject foreign eggs from their nests. We show that where multiple parasitism occurs, rejection itself can be costly, by increasing the risk of host egg loss during subsequent parasite attacks. Chalk-browed Mockingbirds (Mimus saturninus) are heavily parasitized by shiny cowbirds (Molothrus bonariensis), which also puncture eggs in host nests. Mockingbirds struggle to prevent cowbirds puncturing and laying, but seldom remove cowbird eggs once laid. We filmed cowbird visits to nests with manipulated clutch compositions and found that Mockingbird eggs were more likely to escape puncture the more cowbird eggs accompanied them in the clutch. A Monte Carlo simulation of this 'dilution effect', comparing virtual hosts that systematically either reject or accept parasite eggs, shows that acceptors enjoy higher egg survivorship than rejecters in host populations where multiple parasitism occurs. For Mockingbirds or other hosts in which host nestlings fare well in parasitized broods, this benefit might be sufficient to offset the fitness cost of rearing parasite chicks, making egg acceptance evolutionarily stable. Thus, counterintuitively, high intensities of parasitism might decrease or even reverse selection pressure for host defence via egg rejection.
Vanina D Fiorini - One of the best experts on this subject based on the ideXlab platform.
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the wages of violence mobbing by Mockingbirds as a frontline defence against brood parasitic cowbirds
Animal Behaviour, 2013Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:For many hosts of brood-parasitic birds, their frontline of defence is to mob adult parasites that approach the nest. Mobbing is commonly interpreted as an adaptation to prevent the parasite from laying, although to date evidence of this is indirect or anecdotal. We investigated the effectiveness of mobbing by chalk-browed Mockingbirds, Mimus saturninus , as a defence against their parasite, the shiny cowbird, Molothrus bonariensis , using videos of 480 naturally occurring cowbird nest visits and other direct observations. Mockingbirds only occasionally prevented cowbirds from reaching the nest or from laying once in it. More often, cowbirds were able to deposit an egg, aided by their agile flight, rapid laying, endurance of mobbing and, in some cases, opportunistic timing, whereby they approached nests when Mockingbirds were distracted in battle with other cowbirds. Adult parasites present a second threat to hosts, however, in that they try to damage or remove host eggs prior to laying their own. We found that mobbing at the nest significantly reduced the likelihood that cowbirds broke a Mockingbird egg during their visit, despite almost all mobbed visits concluding with a cowbird laying an egg. In this host therefore, the benefit of mobbing must be assessed by two independent measures: prevention of egg laying by the parasite and loss of their own eggs. As Mockingbird eggs that survive a cowbird's visit intact can go on to fledge from parasitized broods, we expect strong selection for mobbing as an antiparasite defence in this host, even though it largely fails to prevent parasitism itself.
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brood parasite eggs enhance egg survivorship in a multiply parasitized host
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ros Gloag, Juan C Reboreda, Vanina D Fiorini, Alex KacelnikAbstract:Despite the costs to avian parents of rearing brood parasitic offspring, many species do not reject foreign eggs from their nests. We show that where multiple parasitism occurs, rejection itself can be costly, by increasing the risk of host egg loss during subsequent parasite attacks. Chalk-browed Mockingbirds (Mimus saturninus) are heavily parasitized by shiny cowbirds (Molothrus bonariensis), which also puncture eggs in host nests. Mockingbirds struggle to prevent cowbirds puncturing and laying, but seldom remove cowbird eggs once laid. We filmed cowbird visits to nests with manipulated clutch compositions and found that Mockingbird eggs were more likely to escape puncture the more cowbird eggs accompanied them in the clutch. A Monte Carlo simulation of this 'dilution effect', comparing virtual hosts that systematically either reject or accept parasite eggs, shows that acceptors enjoy higher egg survivorship than rejecters in host populations where multiple parasitism occurs. For Mockingbirds or other hosts in which host nestlings fare well in parasitized broods, this benefit might be sufficient to offset the fitness cost of rearing parasite chicks, making egg acceptance evolutionarily stable. Thus, counterintuitively, high intensities of parasitism might decrease or even reverse selection pressure for host defence via egg rejection.
Bettina Mahler - One of the best experts on this subject based on the ideXlab platform.
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different recognition cues reveal the decision rules used for egg rejection by hosts of a variably mimetic avian brood parasite
Animal Cognition, 2012Co-Authors: Alicia M De La Colina, Juan C Reboreda, Lorena Pompilio, Mark E Hauber, Bettina MahlerAbstract:Brood parasitism imposes several fitness costs on the host species. To reduce these costs, hosts of avian brood parasites have evolved various defenses, of which egg rejection is the most prevalent. In the face of variable host-parasite mimicry and the costs of egg discrimination itself, many hosts reject only some foreign eggs. Here, we experimentally varied the recognition cues to study the underlying cognitive mechanisms used by the Chalk-browed Mockingbird (Mimus saturninus) to reject the white immaculate eggs laid by the parasitic Shiny Cowbird (Molothrus bonariensis). Immaculate eggs are the only parasite eggs rejected by this host, as it accepts all polymorphic, spotted eggs laid by cowbirds. Using a within-breeding pair experimental design, we tested for the salience of spotting, UV reflectance, and brightness in eliciting rejection. We found that the presence of spotting significantly decreased the probability of rejection while increments in brightness significantly increased rejection frequencies. The cognitive rules underlying Mockingbird rejection behavior can be explained by a decision-making model which predicts changes in the levels of rejection in direct relation to the number of relevant attributes shared between host and parasite eggs.