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While some previous investigations have been made into the effects of vegetation structure on the probability of brood parasitism in reed passerines, the effects of vegetation management remain unclear. Furthermore, we possess little information on how vegetation density influences the probability of brood parasitism in wide-surfaced reed-beds. The aim of this study was to test how vegetation density and reed management by burning influence the probability of cuckoo (Cuculus canorus) brood parasitism in great reed warbler (Acrocephalus arundinaceus) nests in a wide-surfaced reed-bed with pure reed stands. We found that the probability of parasitism was highest in nests constructed in low reed density, with low annual variation of reed density and low annual variation of nest height. Reed management had no effect on the probability of parasitism. Our results suggest that, in wide-surfaced reed-beds with pure reed stands, nests in sparser reed are more exposed to brood parasitism than those concealed in dense reed. Furthermore, low spatio-temporal variation in reed density and nest height benefit brood parasitism, as it provides a relatively constant number of host nests in a similar spatial distribution in the reed-bed from year to year. Vegetation structure was suggested to have an important role in adaptation of hosts' defence against brood parasites. [ABSTRACT FROM AUTHOR]

The 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-effects modelling revealed no year effect 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 affected 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. [ABSTRACT FROM AUTHOR]

We surveyed five reed habitats (mining pond, sand pit, large canal, small canal, and lowland river) in north-western Vojvodina (Serbia) between 2009-2011 to study habitat use and to estimate nesting success in an understudied region of the breeding range of the Great Reed Warbler ( Acrocephalus arundinaceus). Data from 174 nests showed that habitat use differed considerably between habitat types but was not related to the area of the study site or the reed bed. Higher than expected numbers of nests along the small canal and the river suggested that Great Reed Warblers preferred these to other habitats for nesting. Habitat use was closely linked to the availability of reed edges and the quality of the reed stand. Overall Mayfield nesting success was 43%, slightly lower than in northern and western Europe. Nesting success was low along the small and large canal, where brood parasitism by Common Cuckoos ( Cuculus canorus) and nest predation were high because of the nearby presence of tree lines that provided perching sites for cuckoos and predators. Nesting success was intermediate at the mining pond because of high predation pressure and adverse weather, and nesting success was highest in the sand pit (despite high cuckoo parasitism) and the river (despite relatively high predation). Our results suggest that canals can function as ecological traps, which attract edge-preferring Great Reed Warblers but are highly accessible to predators and brood parasites. In contrast, sand pits can be perceptual traps because they provide good resources for nesting but were less attractive to Great Reed Warblers than other habitats. Habitat use in relation to habitat availability thus depends primarily on the availability of reed edges and the quality of the reed stand, whereas nesting success also depends on the characteristics of the surroundings and weather conditions. [ABSTRACT FROM AUTHOR]

In this study, the breeding ecology and behaviour of the Great Reed Warbler, Acrocephalus arundinaceus, was studied at Poyrazlar Lake, Turkey. The breeding period started in the first week of May. The incubation period lasted 14 days. As clutch size increased, the diameter of the nests became larger (r = 0.65). Diameters of nests containing different clutch sizes varied significantly from one another (P < 0.01). However, their height did not change (r = 0.24). There was no significant height difference between nests containing different clutch sizes (P > 0.05). As the nests became farther from the shore, the clutch size and the egg weight increased, because mature adults built their nests on the reeds in deeper areas (r = 0.59, r = 0.73). On the other hand, young breeders showed no location preference in their choice of nest site. The number of the nests showed a positive correlation with the height of reeds (r = 0.80). In all nests, 4 different behaviours (Nest Empty, Sitting, Edge of Nest Waiting, Feeding Nestlings) were observed from the appearance of the first egg until the female left the nest. On average, a given female spent 38.11% of her time away from the nest, 51.84% of her time in incubation, 0.91% of her time around the nest, and 9.24% feeding her nestlings per day. [ABSTRACT FROM AUTHOR]

Many hosts have evolved diverse cognitive mechanisms to recognize and reduce the cost of social parasitism. For example, great reed warblers Acrocephalus arundinaceus can accurately reject closely mimetic eggs of brood parasitic common cuckoos Cuculus canorus. Yet, these same hosts are less effective at identifying and rejecting parasitism when the clutch is parasitized by multiple cuckoo eggs, suggesting a role for discordancy (the rejection of the egg type in the minority of the clutch) and/or online self-referent phenotype matching (the simultaneous viewing of cuckoo and own eggs in the nest) to reject foreign eggs. We tested whether the presence of host’s own eggs is required for the discrimination of foreign eggs by dyeing hosts’ own eggs with one of several colors so that clutches contained (a) 1 dyed and 4 unmanipulated eggs, (b) 3 dyed and 2 unmanipulated eggs, or 5 eggs dyed either (c1) differently or (c2) similarly. Rejection rates of dyed eggs varied widely between different colors and were highest in treatment (a), with 1 dyed egg, compared with treatments with the majority (b) or all (c1 and c2) dyed eggs. However, relative rejection rates of dyed eggs were also consistent among specific colors across treatments, including (c1) and (c2), where no unmanipulated own eggs were available for viewing and irrespective of whether eggs were dyed all different colors (c1) or the same colors (c2). We conclude that these hosts can rely on comparisons of foreign egg colors against an internal recognition template of acceptable (own) egg phenotypes. [ABSTRACT FROM PUBLISHER]

Polygyny typically has negative fitness consequences for secondary females, but may equally impose costs on primary females or even on polygynous males. We investigated how polygynous and monogamous great reed warbler, Acrocephalus arundinaceus, males assist their mates with aggressive nest defence against the common cuckoo, Cuculus canorus, and whether the females adjust their nest defence intensity according to male investment in aggression. Additionally, we investigated whether host social mating status affects host vulnerability to parasitism. We presented taxidermic cuckoo mounts at nests of primary, secondary and monogamous females, and recorded aggressive responses of nest owners. We found that monogamous males defended their nests most aggressively while polygynous males allocated their nest protection effort unevenly between their two mates, responding more vigorously on the primary than secondary nests. In contrast, nest defence intensity of females did not differ with respect to their social status, indicating that females of polygynous males did not compensate for low levels of male aggression. Similarly, we found no differences in natural cuckoo parasitism rates between monogamous, primary and secondary nests. Our results thus suggest that while monogamous females receive more assistance with nest defence than females of polygynous males, this has no effect on the probability of parasitism. [Copyright &y& Elsevier]

When two naturalists with the same name have lived and recorded birds in the same area, confusion must arise. This paper attempts to separate the ornithological contributions of the unknown Thomas Robson from those of his namesake, author of Birds of the Derwent Valley (1896). [ABSTRACT FROM AUTHOR]

The article offers information on a study that explored the role played by weather conditions such as temperature and rainfall in affecting egg colouration in the great reed warbler Acrocephalus arundinaceus. The study found the effect of temperature on some egg colour characteristics with increased eggshell brightness due to increased temperature at laying. It downplays the effect of rainfall on eggshell colouration. Further testing the hypothesis that weather may have an effect on egg appearance through the food availability is proposed in other bird species.

Reproductive success of brood parasites varies considerably both among and within host species, mainly due to differences in host egg-rejection rates and survival of parasitic chicks. Here, we investigated the breeding success of the cuckoo ( Cuculus canorus) in one of its major hosts, the great reed warbler ( Acrocephalus arundinaceus), with respect to host social mating status. In this passerine, polygynous males provide less parental care to their young per nest than monogamous males. Consequently, their less-assisted females may fledge lower numbers of nestlings than monogamous females. This may be especially true for secondary females, which often receive limited or no paternal help with young at all. Based on these findings, we expected higher cuckoo reproductive success in nests of socially monogamous than polygynous great reed warbler males. More specifically, we predicted lower fledging success of cuckoo young in nests of secondary than primary or monogamous females. In line with the prediction, we found higher cuckoo fledging success in nests of monogamous than polygynous males, monogamous nests being more than twice as successful as secondary nests. We detected, however, only a tendency to lower cuckoo success in primary compared to monogamous nests and no differences between primary and secondary nests. Moreover, neither parasitism nor host egg-rejection rates differed among the nests of different status. Our results show, for the first time, that the social mating status of a host may influence the overall reproductive success of a brood parasite and thus should be considered in further studies. [ABSTRACT FROM AUTHOR]

Abstract: Chicks of the brood parasitic common cuckoo (Cuculus canorus) typically monopolize host parental care by evicting all eggs and nestmates from the nest. To assess the benefits of parasitic eviction behaviour throughout the full nestling period, we generated mixed broods of one cuckoo and one great reed warbler (Acrocephalus arundinaceus) to study how hosts divide care between own and parasitic young. We also recorded parental provisioning behaviour at nests of singleton host nestlings or singleton cuckoo chicks. Host parents fed the three types of broods with similar-sized food items. The mass of the cuckoo chicks was significantly reduced in mixed broods relative to singleton cuckoos. Yet, after the host chick fledged from mixed broods, at about 10–12 days, cuckoo chicks in mixed broods grew faster and appeared to have compensated for the growth costs of prior cohabitation by fledging at similar weights and ages compared to singleton cuckoo chicks. These results are contrary to suggestions that chick competition in mixed broods of cuckoos and hosts causes an irrecoverable cost for the developing brood parasite. Flexibility in cuckoo’ growth dynamics may provide a general benefit to ecological uncertainty regarding the realized successes, failures, and costs of nestmate eviction strategies of brood parasites. [Copyright &y& Elsevier]

Offspring sex in birds is maternally determined, thus females are expected to vary brood sex ratio adaptively in response to various environmental and/or genetic conditions preferring one sex to the other sex. However, recent studies provide controversial evidence showing mixed support for adaptive sex manipulation theory. One problem may lie in the fact that only sex ratios at fledging have been used in many of these studies, ignoring post-hatching sex-biased mortality. To validate these results, some authors call for replication of previous researches. Here we examined hatchling sex ratio variation in relation to female mating status in a local population of facultatively polygynous great reed warblers Acrocephalus arundinaceus in Central Europe. In agreement with results of previous works, we found that monogamous and primary females had a higher proportion of sons in their broods than secondary females. These results provide further evidence that great reed warbler females manipulate the sex ratio of their offspring in response to their social status. [ABSTRACT FROM AUTHOR]

One group of commonly found parasites in birds, for which fitness consequences and effects on life history traits have been much debated are Haemosporidian blood parasites. In a long term study population of great reed warblers Acrocephalus arundinaceus in Sweden, previous studies have shown that the Haemosporidian blood parasites are in their chronic phase during the breeding season and that the fitness of infected and non-infected birds are similar. In the present study, we quantified parasite intensity (parasitemia) in 718 adults great reed warblers sampled between 1987 and 1998 for the three most common parasite species; Haemoproteus payevskyi (lineage GRW1), Plasmodium ashfordi (GRW2 ) and Plasmodium relictum (GRW4). We verified that the q-PCR method is accurately quantifying Haemoproteus payevskyi (GRW1) as it was highly correlated with the number of parasites seen under microscope. Frequency of mixed infections with two lineages was significantly higher than expected based on the prevalence of each of the three parasite lineages. The mean level of parasitemia was significantly different for the three lineages and individual birds had repeatable parasitemia levels between years. Females tended to have a higher parasitemia than males for all three parasite lineages combined. Females with higher GRW1 parasitemia tended to arrive later in spring to their breeding sites. There was a negative correlation between parasitemia and number of fledged offspring for GRW1, and a tendency for a negative correlation between GRW2 parasitemia and the proportion of recruiting offspring. Overall our results demonstrate that chronic Haemosporidian infections can have slight but significant effects on host life history traits, and therefore may act as important selective agents in wild bird populations. [ABSTRACT FROM AUTHOR]

The prevalent, and so far most explored, host defense against brood parasitism is egg discrimination. Not only do the hosts differ markedly in their propensity to reject parasitic eggs but rejecters even vary in their egg rejection times. The focus of the present study was to investigate factors potentially responsible for high variation in timing of host egg rejection. As a model species, we chose the great reed warbler Acrocephalus arundinaceus, a cuckoo Cuculus canorus host, with female-restricted egg ejection behavior. We presented a cuckoo dummy near host nests and experimentally parasitized the clutches with a nonmimetic egg. Immediately afterward, we continuously video recorded host behavior to determine egg ejection times accurately. We fitted a regression tree model with the timing of egg ejection as a dependent variable and female-related characteristics (body condition, eggshell coloration, and behavior) as explanatory variables. Only female behavior toward the foreign egg proved to have a significant effect on the timing of egg ejection. Females devoting more time to clutch inspection ejected the egg significantly more quickly than females inspecting their experimentally parasitized clutches only briefly. We discuss our results in the context of known intra- and interspecific differences in host response times toward alien eggs and cognitive mechanisms involved in host egg discrimination processes. [ABSTRACT FROM PUBLISHER]

The great reed warbler, Acrocephalus arundinaceus, is one of the most intensively studied species in the area of vocal behaviour and an important model in studies of sexual selection. We evaluated performance of the whistles produced by different males and examined whether individuals improved their performance over consecutive seasons. Finally, we tested whether the performance of whistles reflected males’ philopatry and harem size. We assessed whistle performance based on duration and consistency. Our analyses showed that great reed warbler males improved the performance of their whistles in subsequent seasons. Whistles became both longer and more consistent from one year to the next. We also found that males’ harem size was significantly related to whistle performance, which in turn reflected philopatry. Subsequent analyses revealed that the performances of polygynous and philopatric males differed significantly from those of monogamous, unpaired and new males. As philopatry is preferred by great reed warbler females, it is in the males’ interest to advertise this feature. Coding philopatry in the songs of individual males seems to be an easy and efficient way of informing females about males’ familiarity with the breeding grounds. The proper performance of difficult double-element whistles, the mastery of which may be time consuming, seems to be a good candidate for indicating males’ philopatry. If so, the quality of whistle syllables may also reflect differences in the general quality of individual males as high performance levels may be associated with both males’ longevity and their ability to learn. [Copyright &y& Elsevier]

The developmental rate of cuckoo embryos and their hatching size is greater than that of host species, which may require more nutrient resources in the egg and more intensive gas exchange during development. In the present study, we compared various egg characteristics of a brood parasite, the common cuckoo Cuculus canorus, and its frequent host, the great reed warbler Acrocephalus arundinaceus. As maternally-derived testosterone is known to enhance growth rate of embryos and hatchlings, cuckoo eggs are expected to contain higher concentration of testosterone than host eggs. In addition, we expected higher concentration of antioxidants in cuckoo eggs to protect embryos from oxidative stress associated with accelerated growth. Our results showed that cuckoo eggs had thicker shells and higher pore density than great reed warbler eggs. Yolk was significantly heavier in cuckoo eggs and contained higher concentrations of carotenoids and vitamin E, however, yolk androgen and immunoglobulin concentrations were lower in cuckoo eggs as compared to great reed warbler eggs. We also examined whether eggshell colour was associated to egg quality, and detected a positive association between blue-green chroma and yolk antioxidant concentration in both species, suggesting that eggshell colour reflects the antioxidant investment of the female into the eggs. Our results suggest that cuckoo females increase the size, growth rate and competitive ability of their young by providing them with more nutrients and more dietary antioxidants for embryonic development, and not through elevated yolk testosterone or antibody levels. In addition, increased porosity of cuckoo eggshells may allow embryos to develop more rapidly because of a greater capacity of gas exchange. [ABSTRACT FROM AUTHOR]

Eggshell colour patterns play a crucial role in avian host–parasite coevolution. In contrast to many experiments investigating general host egg discrimination abilities, studies testing where specific recognition cues are located on the eggshells (on blunt, sharp or both egg poles) are lacking. Previous studies suggested that discrimination cues might be located at the blunt egg pole, where the shell patterning is typically concentrated. We tested this hypothesis experimentally in species subject to interspecific (great reed warblers Acrocephalus arundinaceus, reed warblers A. scirpaceus), and also intraspecific parasitism (song thrushes Turdus philomelos, blackbirds T. merula). We examined host responses towards two types of intraspecific eggs painted non-mimetic immaculate blue either at blunt or sharp poles. All four species rejected eggs manipulated at the blunt pole at significantly higher rates, indicating that they perceive the critical recognition cues in the same egg part. Thus, the presence of egg recognition cues at the blunt egg pole may be a general phenomenon in birds parasitized by both intraspecific and interspecific parasites. [ABSTRACT FROM AUTHOR]

Quantitative genetic parameters are nowadays more frequently estimated with restricted maximum likelihood using the 'animal model' than with traditional methods such as parent-offspring regressions. These methods have however rarely been evaluated using equivalent data sets. We compare heritabilities and genetic correlations from animal model and parent-offspring analyses, respectively, using data on eight morphological traits in the great reed warbler (Acrocephalus arundinaceus). Animal models were run using either mean trait values or individual repeated measurements to be able to separate between effects of including more extended pedigree information and effects of replicated sampling from the same individuals. We show that the inclusion of more pedigree information by the use of mean traits animal models had limited effect on the standard error and magnitude of heritabilities. In contrast, the use of repeated measures animal model generally had a positive effect on the sampling accuracy and resulted in lower heritabilities; the latter due to lower additive variance and higher phenotypic variance. For most trait combinations, both animal model methods gave genetic correlations that were lower than the parent-offspring estimates, whereas the standard errors were lower only for the mean traits animal model. We conclude that differences in heritabilities between the animal model and parent-offspring regressions were mostly due to the inclusion of individual replicates to the animal model rather than the inclusion of more extended pedigree information. Genetic correlations were, on the other hand, primarily affected by the inclusion of more pedigree information. This study is to our knowledge the most comprehensive empirical evaluation of the performance of the animal model in relation to parent-offspring regressions in a wild population. Our conclusions should be valuable for reconciliation of data obtained in earlier studies as well as for future meta-analyses utilizing estimates from both traditional methods and the animal model. [ABSTRACT FROM AUTHOR]

The article presents a study which aims at analyzing the presence of the Blackheaded Weaver Ploceus melanocephalus in the regions of Iberian Peninsula in its early stages of invasion. According to the research, melanocephalus competes with other native species including the Great Reed Warbler Acrocephalus arundinaceus and the Eurasian Reed Warbler A. scirpaceous.