The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Dennis Hasselquist - One of the best experts on this subject based on the ideXlab platform.
-
intralocus sexual conflict over wing length in a wild migratory bird
The American Naturalist, 2014Co-Authors: Maja Tarka, Mikael Åkesson, Dennis Hasselquist, Bengt HanssonAbstract:AbstractIntralocus sexual conflict (ISC) occurs when males and females have different adaptive peaks but are constrained from evolving sexual dimorphism because of shared genes. Implications of this conflict on evolutionary dynamics in wild populations have not been investigated in detail. In comprehensive analyses of selection, heritability, and genetic correlations, we found evidence for an ISC over wing length, a key trait for flight performance and migration, in a long-term study of wild great reed warblers (Acrocephalus arundinaceus). We found moderate sexual dimorphism, high heritability, moderate sexually antagonistic selection, and strong positive cross-sex genetic correlation in wing length, together supporting the presence of ISC. A negative genetic correlation between male wing length and female fitness indicated that females inheriting alleles for longer wings from their male relatives also inherited lower fitness. Moreover, cross-sex genetic correlations imposed constraint on the predicted mi...
-
daily energy expenditure of singing great reed warblers Acrocephalus arundinaceus
Journal of Avian Biology, 2008Co-Authors: Dennis Hasselquist, Staffan BenschAbstract:According to honest signalling theory, signals must be costly to produce to retain information about the signaller's quality. The song produced by male birds during breeding is a vocal "ornament" used for intra- and inter-sexual purposes. The energetic cost of this vocal signal remains a contentious issue. We used the doubly labelled water method to measure field metabolic rate by estimating CO2 production and then convert this to daily energy expenditure (DEE) in great reed warbler males singing under natural conditions (10 at low to moderate intensity and 7 at very high intensity from dawn to dusk). There was a significant positive relationship between singing intensity and DEE. From this relationship we extrapolated the average DEE for intensely singing males (i.e., males producing song sounds 50% of the time and hence sitting at their elevated song post in the top of a reed stem more or less continuously throughout the similar to 20 h of daylight) to 3.3xBMR (basal metabolic rate) and for non-singing males to 2.2xBMR. The mean DEE measured for the seven males singing with very high intensity was 3.1xBMR. The maximum measured DEE for a single male was 3.9xBMR, i.e. close to the maximum sustainable DEE (4xBMR), and the minimum DEE was 2.1xBMR for a male singing at very low intensity. These results imply that producing intensive advertising song in birds may incur a substantial cost in terms of increased energy expenditure. (Less)
-
Migration, stopover and moult of the great reed warbler Acrocephalus arundinaceus in Ghana, West Africa
Ibis, 2008Co-Authors: Anders Hedenström, Dennis Hasselquist, Staffan Bensch, Mary Lockwood, Ulf OttossonAbstract:We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid-November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March-April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.
-
Rapid moult among palaearctic passerines in West Africa- an adaptation to the oncoming dry season?
Ibis, 2008Co-Authors: Staffan Bensch, Dennis Hasselquist, Anders Hedenström, Ulf OttossonAbstract:Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides, Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season.
-
An analysis of hatching success in the great reed warbler Acrocephalus arundinaceus
Oikos, 2007Co-Authors: Jonas Knape, Bengt Hansson, Staffan Bensch, Martin Sköld, Niclas Jonzén, Mikael Åkesson, Dennis HasselquistAbstract:Hatching success is a potentially important fitness component for avian species. Previous studies of hatching success in natural populations have primarily focused on effects of inbreeding but a general understanding of variation in hatching success is lacking. We analyse data on hatching success in a population of great reed warblers Acrocephalus arundinaceus in Lake Kvismaren in south central Sweden. The effects of a range of covariates, including three measures of inbreeding as well as effects of classifications in the data (such as identities of individuals), on hatching success are analysed simultaneously. This is done by means of fitting Bayesian binomial mixed models using Markov chain Monte Carlo methods. Using random effects for each individual parent we check for unexplained variation in hatching success among male and female individuals and compare it to effects of covariates such as degree of inbreeding. Model selection showed that there was a significant amount of unexplained variation in hatching probability between females. This was manifested by a few females laying eggs with a substantially lower hatching success than the majority of the females. The deviations were of the same order of magnitude as the significant effect of parent relatedness on hatching success. Whereas the negative effect of parent relatedness on hatchability is an expression of inbreeding, the female individual effect is not due to inbreeding and could reflect maternal effects, that females differ in fertilisation and/or incubation ability, or an over representation of genetic components from the female acting on the early developing embryo.
Staffan Bensch - One of the best experts on this subject based on the ideXlab platform.
-
daily energy expenditure of singing great reed warblers Acrocephalus arundinaceus
Journal of Avian Biology, 2008Co-Authors: Dennis Hasselquist, Staffan BenschAbstract:According to honest signalling theory, signals must be costly to produce to retain information about the signaller's quality. The song produced by male birds during breeding is a vocal "ornament" used for intra- and inter-sexual purposes. The energetic cost of this vocal signal remains a contentious issue. We used the doubly labelled water method to measure field metabolic rate by estimating CO2 production and then convert this to daily energy expenditure (DEE) in great reed warbler males singing under natural conditions (10 at low to moderate intensity and 7 at very high intensity from dawn to dusk). There was a significant positive relationship between singing intensity and DEE. From this relationship we extrapolated the average DEE for intensely singing males (i.e., males producing song sounds 50% of the time and hence sitting at their elevated song post in the top of a reed stem more or less continuously throughout the similar to 20 h of daylight) to 3.3xBMR (basal metabolic rate) and for non-singing males to 2.2xBMR. The mean DEE measured for the seven males singing with very high intensity was 3.1xBMR. The maximum measured DEE for a single male was 3.9xBMR, i.e. close to the maximum sustainable DEE (4xBMR), and the minimum DEE was 2.1xBMR for a male singing at very low intensity. These results imply that producing intensive advertising song in birds may incur a substantial cost in terms of increased energy expenditure. (Less)
-
dynamics of parasitemia of malaria parasites in a naturally and experimentally infected migratory songbird the great reed warbler Acrocephalus arundinaceus
Experimental Parasitology, 2008Co-Authors: Pavel Zehtindjiev, Bengt Hansson, Gediminas Valkiūnas, Mihaela Ilieva, Helena Westerdahl, Staffan BenschAbstract:Little is known about the development of infection of malaria parasites of the genus Plasmodium in wild birds. We used qPCR, targeting specific mitochondrial lineages of Plasmodium ashfordi (GRW2) and Plasmodium relictum (GRW4), to monitor changes in intensities of parasitemia in captive great reed warblers Acrocephalus arundinaceus from summer to spring. The study involved both naturally infected adults and experimentally infected juveniles. The experiment demonstrated that P. ashfordi and P. relictum lineages differ substantially in several life-history traits (e.g. prepatent period and dynamics of parasitemia) and that individual hosts show substantial differences in responses to these infections. The intensity of parasitemia of lineages in mixed infections co-varied positively, suggesting a control mechanism by the host that is general across the parasite lineages. The intensity of parasitemia for individual hosts was highly repeatable suggesting variation between the host individuals in their genetic or acquired control of the infections. In future studies, care must be taken to avoid mixed infections in wild caught donors, and when possible use mosquitoes for the experiments as inoculation of infectious blood ignores important initial stages of the contact between the bird and the parasite.
-
Migration, stopover and moult of the great reed warbler Acrocephalus arundinaceus in Ghana, West Africa
Ibis, 2008Co-Authors: Anders Hedenström, Dennis Hasselquist, Staffan Bensch, Mary Lockwood, Ulf OttossonAbstract:We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid-November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March-April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.
-
Rapid moult among palaearctic passerines in West Africa- an adaptation to the oncoming dry season?
Ibis, 2008Co-Authors: Staffan Bensch, Dennis Hasselquist, Anders Hedenström, Ulf OttossonAbstract:Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides, Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season.
-
An analysis of hatching success in the great reed warbler Acrocephalus arundinaceus
Oikos, 2007Co-Authors: Jonas Knape, Bengt Hansson, Staffan Bensch, Martin Sköld, Niclas Jonzén, Mikael Åkesson, Dennis HasselquistAbstract:Hatching success is a potentially important fitness component for avian species. Previous studies of hatching success in natural populations have primarily focused on effects of inbreeding but a general understanding of variation in hatching success is lacking. We analyse data on hatching success in a population of great reed warblers Acrocephalus arundinaceus in Lake Kvismaren in south central Sweden. The effects of a range of covariates, including three measures of inbreeding as well as effects of classifications in the data (such as identities of individuals), on hatching success are analysed simultaneously. This is done by means of fitting Bayesian binomial mixed models using Markov chain Monte Carlo methods. Using random effects for each individual parent we check for unexplained variation in hatching success among male and female individuals and compare it to effects of covariates such as degree of inbreeding. Model selection showed that there was a significant amount of unexplained variation in hatching probability between females. This was manifested by a few females laying eggs with a substantially lower hatching success than the majority of the females. The deviations were of the same order of magnitude as the significant effect of parent relatedness on hatching success. Whereas the negative effect of parent relatedness on hatchability is an expression of inbreeding, the female individual effect is not due to inbreeding and could reflect maternal effects, that females differ in fertilisation and/or incubation ability, or an over representation of genetic components from the female acting on the early developing embryo.
Bengt Hansson - One of the best experts on this subject based on the ideXlab platform.
-
intralocus sexual conflict over wing length in a wild migratory bird
The American Naturalist, 2014Co-Authors: Maja Tarka, Mikael Åkesson, Dennis Hasselquist, Bengt HanssonAbstract:AbstractIntralocus sexual conflict (ISC) occurs when males and females have different adaptive peaks but are constrained from evolving sexual dimorphism because of shared genes. Implications of this conflict on evolutionary dynamics in wild populations have not been investigated in detail. In comprehensive analyses of selection, heritability, and genetic correlations, we found evidence for an ISC over wing length, a key trait for flight performance and migration, in a long-term study of wild great reed warblers (Acrocephalus arundinaceus). We found moderate sexual dimorphism, high heritability, moderate sexually antagonistic selection, and strong positive cross-sex genetic correlation in wing length, together supporting the presence of ISC. A negative genetic correlation between male wing length and female fitness indicated that females inheriting alleles for longer wings from their male relatives also inherited lower fitness. Moreover, cross-sex genetic correlations imposed constraint on the predicted mi...
-
stable isotope ratios in winter grown feathers of great reed warblers Acrocephalus arundinaceus clamorous reed warblers a stentoreus and their hybrids in a sympatric breeding population in kazakhstan
Ibis, 2011Co-Authors: Elizabeth Yohannes, Raymond W Lee, Marc Jochimsen, Bengt HanssonAbstract:Analyses of the stable isotope composition of feathers can provide significant insight into the spatial structure of bird migration. We collected feathers from Great Reed Warblers Acrocephalus arundinaceus, Clamorous Reed Warblers A. stentoreus and a small sample of their hybrids in a sympatric breeding population in Kazakhstan to assess natural variation in stable isotope signatures and delineate wintering sites. The Great Reed Warbler is a long-distance migrant that overwinters in sub-Saharan Africa, whereas the Clamorous Reed Warbler performs a short-distance migration to the Indian sub-continent. Carbon (delta C-13), nitrogen (delta N-15) and deuterium (delta D) isotope signatures were obtained from winter-grown feathers of adult birds. There were highly significant differences in delta D and less significant differences in delta C-13 between Great and Clamorous Reed Warblers. Thus, our results show that the stable isotope technique, and in particular the deuterium (delta D) signal, resolves continental variation in winter distribution between these closely related Acrocephalus species with sympatric natal origin. The isotope signatures of hybrid Great x Clamorous Reed Warblers clustered with those of the Great Reed Warblers. Hence, a parsimonious suggestion is that the hybrids undergo moult in Afrotropical wintering grounds, as do the Great Reed Warblers. The observed delta D values fell within the range of expected values based on available precipitation data collected at precipitation stations across the wintering continents of each species. However, the power to predict the winter origin of birds in our study system using these data was weak as the expected values ranged widely at this broad continental scale. (Less)
-
common cuckoo cuculus canorus parasitism antiparasite defence and gene flow in closely located populations of great reed warblers Acrocephalus arundinaceus
Journal of Avian Biology, 2008Co-Authors: Csaba Moskát, Lilla Barabas, Istvan Bartol, Bengt Hansson, Zsolt KarczaAbstract:In Hungary an unusually high rate of parasitism on the great reed warbler Acrocephalus arundinaceus by the common cuckoo Cuculus canorus has been maintained for at least the last one hundred years. We evaluated parasitism rate, antiparasite defence and genetic differentiation among Hungarian great reed warblers at three sites located 40-130 km from each other, where hosts suffered from a high (41-68%), moderate (11%), and almost no (< 1%) parasitism. We were especially interested in whether the level of antiparasite defence was related to the local parasitism rate, and, if not, to understand why. There was no difference among the three sites in the responses to experimental parasitism by non-mimetic model cuckoo eggs (rejection rate 71-82%), which can be explained by strong gene flow between populations: there was low level of philopatry and no genetic differentiation in the region. Reproductive success of the host in the heavily parasitised site was about 54% of that in the unparasitised site, indicating that long-term persistence of host populations in highly exploited areas depends on continuous immigration. (Less)
-
dynamics of parasitemia of malaria parasites in a naturally and experimentally infected migratory songbird the great reed warbler Acrocephalus arundinaceus
Experimental Parasitology, 2008Co-Authors: Pavel Zehtindjiev, Bengt Hansson, Gediminas Valkiūnas, Mihaela Ilieva, Helena Westerdahl, Staffan BenschAbstract:Little is known about the development of infection of malaria parasites of the genus Plasmodium in wild birds. We used qPCR, targeting specific mitochondrial lineages of Plasmodium ashfordi (GRW2) and Plasmodium relictum (GRW4), to monitor changes in intensities of parasitemia in captive great reed warblers Acrocephalus arundinaceus from summer to spring. The study involved both naturally infected adults and experimentally infected juveniles. The experiment demonstrated that P. ashfordi and P. relictum lineages differ substantially in several life-history traits (e.g. prepatent period and dynamics of parasitemia) and that individual hosts show substantial differences in responses to these infections. The intensity of parasitemia of lineages in mixed infections co-varied positively, suggesting a control mechanism by the host that is general across the parasite lineages. The intensity of parasitemia for individual hosts was highly repeatable suggesting variation between the host individuals in their genetic or acquired control of the infections. In future studies, care must be taken to avoid mixed infections in wild caught donors, and when possible use mosquitoes for the experiments as inoculation of infectious blood ignores important initial stages of the contact between the bird and the parasite.
-
An analysis of hatching success in the great reed warbler Acrocephalus arundinaceus
Oikos, 2007Co-Authors: Jonas Knape, Bengt Hansson, Staffan Bensch, Martin Sköld, Niclas Jonzén, Mikael Åkesson, Dennis HasselquistAbstract:Hatching success is a potentially important fitness component for avian species. Previous studies of hatching success in natural populations have primarily focused on effects of inbreeding but a general understanding of variation in hatching success is lacking. We analyse data on hatching success in a population of great reed warblers Acrocephalus arundinaceus in Lake Kvismaren in south central Sweden. The effects of a range of covariates, including three measures of inbreeding as well as effects of classifications in the data (such as identities of individuals), on hatching success are analysed simultaneously. This is done by means of fitting Bayesian binomial mixed models using Markov chain Monte Carlo methods. Using random effects for each individual parent we check for unexplained variation in hatching success among male and female individuals and compare it to effects of covariates such as degree of inbreeding. Model selection showed that there was a significant amount of unexplained variation in hatching probability between females. This was manifested by a few females laying eggs with a substantially lower hatching success than the majority of the females. The deviations were of the same order of magnitude as the significant effect of parent relatedness on hatching success. Whereas the negative effect of parent relatedness on hatchability is an expression of inbreeding, the female individual effect is not due to inbreeding and could reflect maternal effects, that females differ in fertilisation and/or incubation ability, or an over representation of genetic components from the female acting on the early developing embryo.
Marcel Honza - One of the best experts on this subject based on the ideXlab platform.
-
Within-season dispersal does not protect re-nesting great reed warblers (Acrocephalus arundinaceus) from repeated common cuckoo (Cuculus canorus) parasitism
Behavioral Ecology and Sociobiology, 2020Co-Authors: Kateřina Sosnovcová, Marcel Honza, Petr Prochazka, Milica Požgayová, Jaroslav KolečekAbstract:The co-evolutionary arms race between brood parasites and their hosts involves stepwise adaptive changes on the side of the parasites as well as hosts. In response to avian brood parasitism, host females may eject a parasitic egg, bury the parasitized clutch or desert it. After nest desertion, females commonly re-nest and may move further to avoid being parasitized again. Here we tested whether and under which conditions the within-season re-nesting prevents brood parasitism in the great reed warbler ( Acrocephalus arundinaceus ). We analysed 78 re-nesting events of 58 naturally parasitized host females that deserted their nests in response to the common cuckoo ( Cuculus canorus ) parasitism. The parasitism rate in the replacement nests of these females was 60%. Most of these females built their replacement nests less than 143 m from the previous nests. The probability for replacement nests to be parasitized increased with increasing instantaneous parasitism rate but not with the re-nesting distance or timing of the replacement clutch. We explain this by the high level of cuckoo parasitism across the whole study site during the major part of the breeding season. To better understand the patterns and consequences of host re-nesting behaviour, further studies in other host populations with different levels of cuckoo parasitism would be desirable. Significance statement Although various factors affecting avian breeding dispersal have been studied, little is known about the relationship between the within-season re-nesting distances and fate of replacement nests. Moreover, there is a lack of studies focusing on the consequences of re-nesting dispersal in response to brood parasitism and, to our best knowledge, this is the first study investigating this topic in a host of an evictor parasite.
-
Caught on camera: circumstantial evidence for fatal mobbing of an avian brood parasite by a host
Journal of Vertebrate Biology, 2020Co-Authors: Michal Šulc, Petr Prochazka, Milica Požgayová, Kateřina Sosnovcová, Gabriela Štětková, Jan Studecký, Marcel HonzaAbstract:Hosts have evolved a multiplicity of defensive responses against avian brood parasites. One of them is mobbing behaviour which often includes direct contact attacks. These aggressive strikes may not only distract the parasites but may also be fatal to them, as documented by cases of dead brood parasite females found near host nests. Here, we present the first video-recording of a great reed warbler (Acrocephalus arundinaceus) host whose vigorous nest defence appears to directly lead to the death of a female common cuckoo (Cuculus canorus). We suggest that the chance of parasite death probably rises with the presence of unfavourable factors, such as water below the nest. Our observation supports previous suggestions that hosts may pose a lethal danger to their parasites.
-
Great Reed Warbler singing behavior and conspicuous song structures are not nest-location cues for the Common Cuckoo
Journal of Ornithology, 2017Co-Authors: Miroslav Capek, Marcel Honza, Petr Prochazka, Tereza Petrusková, Zuzana Šebelíková, Jesús Campos Serrano, Milica PožgayováAbstract:Drosselrohrsänger ( Acrocephalus arundinaceus ): Weder ihr Singverhalten, noch auffallende Strukturelemente in den Gesängen dienen dem Kuckuck ( Cuculus canorus ) als Hinweise auf den Standort der Nester Es gibt Fälle, in denen Brutparasiten von akustischen oder visuellen Signalen, die mit der Brutaktivität des Wirts verbunden sind, angezogen werden. Wir untersuchten eine Population des Drosselrohrsängers ( Acrocephalus arundinaceus ), in der jedes Jahr 30–50% der Nester vom Kuckuck ( Cuculus canorus ) parasitiert werden. Hierfür beobachteten wir die Wirts-Männchen und quantifizierten ihre mit dem Singen verknüpften Verhaltenselemente, inklusive der mit Singen verbrachten Zeit, ihrer räumlichen Bewegungsmuster und der Zeit, die sie singend in ganz bestimmten Körperstellungen an einem Schilfhalm zubrachten. Wir sagten vorher, daß Nester von stärker exponierten Männchen (z. B. jenen, die mehr Zeit mit Singen verbrachten, beim Herumhüpfen größere Entfernungen zurücklegten und mehr Zeit auf ein und demselben Schilfrohr hockten) eher parasitiert würden als weniger exponierte Männchen. Zusätzlich maßen wir die Längen derjenigen charakteristischen Gesangselementen, die am klarsten herauszuhören und damit für die Kuckucke potentiell am auffälligsten waren. Wir zählten die Anzahl der Kara-Silben pro Gesang und bestimmten deren Frequenzspitzen. Da diese Gesangselemente eher niedrigere Frequenzen aufweisen und somit über längere Entfernungen zu hören sind, mutmaßten wir, dass Männchen, die mehr Kara-Silben produzierten, oder mehr solche mit niedrigeren Frequenzen, häufiger parasitiert würden. Wir fanden jedoch heraus, dass weder das Sing-Verhalten der Männchen, noch auffällige Gesangsmuster signifikante Prädiktoren für Parasitismus waren. Einzig die Sichtbarkeit der Wirts-Nester für die Parasiten, von uns als Kovariante behandelt, stellte sich als signifikant heraus. Leicht sichtbare Nester wurden häufiger als versteckte Nester parasitiert. Unsere Ergebnisse legen nahe, dass Kuckucks-Weibchen die Nest-Sichtbarkeit oder aber Verhaltensweisen der Wirte, die nichts mit dem Gesang der Männchen zu tun haben, als Mittel benutzen, Nester von Wirten zu finden. In some systems, brood parasites may be attracted by vocal or visual signals connected with host breeding. We studied a Great Reed Warbler ( Acrocephalus arundinaceus ) population where annually 30–50% of nests are parasitized by the Common Cuckoo ( Cuculus canorus ). We observed host males and quantified their song-related behaviors, including time spent singing, distance of movements and time spent singing in particular positions on a reed stem. We predicted that nests of more exposed males (i.e., those spending more time singing, moving a larger total distance, and spending more time on the top of stems) would be more likely to be parasitized than the nests of less exposed males. Additionally, we measured male song characteristics that we assumed to be most audible, and thus potentially the most conspicuous to the Common Cuckoo. We counted the number of “kara” syllables per song and measured their peak frequencies. Since these song structures are of low frequency and thus might be audible at longer distances, we predicted that males producing more kara syllables or uttering kara syllables of lower peak frequencies would also be more parasitized. However, we found that neither male singing behavior nor conspicuous song characteristics were significant predictors of parasitism. Only the visibility of host nests to the parasite, which we treated as a covariate, proved to be significant. Visible nests were more often parasitized than hidden nests. Our findings indicate that the Cuckoo females use nest visibility, or host behavior other than male singing, as the cue to locate host nests.
-
Experimental enlargement of nest size does not increase risk of predation or brood parasitism in the Great Reed Warbler Acrocephalus arundinaceus
Ibis, 2015Co-Authors: Václav Jelínek, Petr Prochazka, Marcel HonzaAbstract:We assessed whether nest size affects the probability of nest loss using dyads of large and small (large being twice the size of small) inactive Great Reed Warbler Acrocephalus arundinaceus nests placed at similar sites in Great Reed Warbler territories. Large nests were not predated significantly more frequently than small nests. Experimentally enlarged active Great Reed Warbler nests suffered non-significantly higher predation compared with non-manipulated control nests. Our experiments did not support the nest-size hypothesis and suggested that nest size does not appear to be a factor affecting the risk of nest predation in this species. The probability of brood parasitism by the Common Cuckoo Cuculus canorus was also unaffected by experimental nest enlargement, supporting the commonly accepted hypothesis that the Common Cuckoo searches for suitable host nests by host activity during nest building rather than nest size.
-
Within‐ and between‐season repeatability of eggshell colouration in the great reed warbler Acrocephalus arundinaceus
Journal of Avian Biology, 2012Co-Authors: Marcel Honza, Petr Prochazka, Milica PožgayováAbstract:While avian eggshell colouration has attracted biologists for decades, little is known about its variation within individuals. Th e main goal of this study was to explore within- and between-season repeatability of eggshell appearance in the great reed warbler Acrocephalus arundinaceus . To achieve this, we measured eggshell refl ectance of fi rst and replacement clutches of individual females within one breeding season, and the refl ectance of their fi rst clutches in two following breeding seasons. As environmental conditions may aff ect egg colouration, repeatability was estimated from linear mixed-eff ects models where we initially included temperature and rainfall during egg laying, as well as year, clutch order and egg-laying date as fi xed eff ects, and clutch identity nested in females as random eff ects. Eggshell appearance within clutches showed moderate repeatability, while both within- and between-season repeatability in clutch colouration for individual females was low. Our fi ndings indicate that low intra-clutch variation may have a function within the context of brood parasitism, i.e. in facilitating host recognition of alien eggs. With variable eggs between successive clutches, however, host females may need to relearn the appearance of their eggs with every clutch they lay. Th is could represent a signifi cant constraint for host egg-discrimination abilities. Yet, whether environmental or intrinsic physiological factors are responsible for the variation in eggshell colouration between successive clutches of the same females still remain to be discovered.
Csaba Moskát - One of the best experts on this subject based on the ideXlab platform.
-
anti parasitic egg rejection by great reed warblers Acrocephalus arundinaceus tracks differences along an eggshell color gradient
Behavioural Processes, 2019Co-Authors: Mikus Abolinsabols, Csaba Moskát, Daniel Hanley, Tomas Grim, Mark E HauberAbstract:Abstract One of the most effective defenses against avian brood parasitism is the rejection of the foreign egg from the host’s nest. Until recently, most studies have tested whether hosts discriminate between own and foreign eggs based on their absolute differences in avian-perceivable eggshell coloration and maculation. However, recent studies suggest that hosts may instead contrast egg appearances across a directional eggshell color gradient. We assessed which discrimination rule best explained egg rejection by great reed warblers Acrocephalus arundinaceus , a frequent host to an egg-mimetic race of common cuckoos Cuculus canorus . We deployed 3D-printed model eggs varying in blue-green to brown coloration and in the presence of maculation. Using visual modeling, we calculated the absolute chromatic and achromatic just-noticeable differences (JNDs), as well as directional JNDs across a blue-green to brown egg color gradient, between host and model eggs. While most model eggs were rejected by great reed warblers, browner eggs were rejected with higher probability than more blue-green eggs, and the rejection probability did not depend on maculation. Directional egg color discrimination shown here and in a suite of recent studies on other host species may shape the cognitive decision rules that hosts use to recognize foreign eggs and affect the course of evolution in parasitic egg mimicry.
-
multiple parasitism reduces egg rejection in the host Acrocephalus arundinaceus of a mimetic avian brood parasite cuculus canorus
Journal of Comparative Psychology, 2019Co-Authors: Thomas J Manna, Csaba Moskát, Lainga Tong, Zachary Aidala, Mark Erno HauberAbstract:A host that has been targeted by an avian brood parasite can recover most of its potential fitness loss by ejecting the foreign egg(s) from its nest. The propensity for some hosts to engage in egg rejection behavior has put selective pressure on their parasites to evolve mimetic eggshells resembling the host's own shell colors and maculation. In turn, hosts have counterevolved increasingly more sophisticated detection methods such as narrowing visual egg acceptance thresholds or using social cues to recognize parasitism. However, multiple cognitive mechanisms acting simultaneously could theoretically interfere with one another and ultimately decrease egg rejection accuracy, especially if these heuristics yield differing targets for rejection. By painting hosts own eggs, we studied a host species of the common cuckoo Cuculus canorus, the great reed warbler Acrocephalus arundinaceus, and tested its responses to the presence of "foreign" eggs of varying quantity, colors, and uniformity. Using reflectance spectra of egg background coloration and avian perceptual modeling, we then estimated the sensory thresholds triggering egg rejection by this host for each treatment. As previously reported, rejection rates were positively related to the perceptual distance between own and foreign eggs in the nests in all treatments. However, rejection thresholds were more permissive (error prone) both with greater proportions of foreign eggs per clutch and/or when the suite of foreign eggs was perceptually more variable within the nest. These results suggest that parasites, through multiple parasitism, can partially overcome the evolution of hosts' recognition of mimetic parasite eggs. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
-
common cuckoos cuculus canorus affect the bacterial diversity of the eggshells of their great reed warbler Acrocephalus arundinaceus hosts
PLOS ONE, 2018Co-Authors: Nikoletta Geltsch, Zoltan Elek, Lászlo Manczinger, Csaba Vágvölgyi, Csaba MoskátAbstract:The common cuckoo (Cuculus canorus) is an avian brood parasite, laying its eggs in the nests of other bird species, where these hosts incubate the parasitic eggs, feed and rear the nestlings. The appearance of a cuckoo egg in a host nest may change the bacterial community in the nest. This may have consequences on the hatchability of host eggs, even when hosts reject the parasitic egg, typically within six days after parasitism. The present study revealed the bacterial community of cuckoo eggshells and those of the great reed warbler (Acrocephalus arundinaceus), one of the main hosts of cuckoos. We compared host eggs from non-parasitized clutches, as well as host and cuckoo eggs from parasitized clutches. As incubation may change bacterial assemblages on eggshells, we compared these egg types in two stages: the egg-laying stage, when incubation has not been started, and the mid-incubation stage (ca. on days 5-7 in incubation), where heat from the incubating female dries eggshells. Our results obtained by the 16S rRNA gene sequencing technique showed that fresh host and cuckoo eggs had partially different bacterial communities, but they became more similar during incubation in parasitized nests. Cluster analysis revealed that fresh cuckoo eggs and incubated host eggs in unparasitized nests (where no cuckoo effect could have happened) were the most dissimilar from the other groups of eggs. Cuckoo eggs did not reduce the hatchability of great reed warbler eggs. Our results on the cuckoo-great reed warbler relationship supported the idea that brood parasites may change bacterial microbiota in the host nest. Further studies should reveal how bacterial communities of cuckoo eggshells may vary by host-specific races (gentes) of cuckoos.
-
no change in common cuckoo cuculus canorus parasitism and great reed warblers Acrocephalus arundinaceus egg rejection after seven decades
Journal of Avian Biology, 2015Co-Authors: Aniko Zolei, Csaba MoskátAbstract:Th e coevolutionary process among avian brood parasites and their hosts involves stepwise changes induced by the antagonistic selection pressures of one on the other. As long-term data on an evolutionary scale is almost impossible to obtain, most studies can only show snapshots of such processes. Information on host behaviour, such as changes in egg rejection rates and the methods of rejection are scarce. In Hungary there is an interesting case between the common cuckoo Cuculus canorus and the great reed warbler Acrocephalus arundinaceus, where the level of parasitism is unusually high (around 50%). We compared host rejection rates and methods of rejection from within our own project to that of an early study carried out and published almost 70 yr ago in the same region. Our comparisons revealed high and stable rates of parasitism (range: 52 – 64%), and marked fl uctuations in the ratio of multiply parasitized nests (range: 24 – 52%). No difference was revealed in egg rejection rates after 7 decades (34 – 39%). Linear mixed-eff ects modelling revealed no year eff ect on the type host responses toward the parasitic egg(s) during the years of study (categorized as acceptance, ejection, burial, and nest desertion). Cuckoo egg rejection was primarily aff ected by the type of parasitism, as more cuckoo eggs were rejected during single parasitism than from multiply parasitized nests. Our comparison did not reveal any directional changes in this cuckoo – host relationship, except a slight decrease in the frequency of multiple parasitism, which is likely to be independent from coevolutionary processes.
-
Naïve hosts of avian brood parasites accept foreign eggs, whereas older hosts fine-tune foreign egg discrimination during laying
Frontiers in Zoology, 2014Co-Authors: Csaba Moskát, Mark Erno HauberAbstract:Background Many potential hosts of social parasites recognize and reject foreign intruders, and reduce or altogether escape the negative impacts of parasitism. The ontogenetic basis of whether and how avian hosts recognize their own and the brood parasitic eggs remains unclear. By repeatedly parasitizing the same hosts with a consistent parasitic egg type, and contrasting the responses of naive and older breeders, we studied ontogenetic plasticity in the rejection of foreign eggs by the great reed warbler (Acrocephalus arundinaceus), a host species of the common cuckoo (Cuculus canorus).
