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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] more...

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] more...

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] more...

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] more...