Katalin Varga

Distribution of the Eastern knapweed fritillary (Melitaea ornata Christoph, 1893) (Lepidoptera: Nymphalidae): past, present and future

Climatic change during the Quaternary resulted in periodical range restrictions and expansions in most temperate species. Although some repetitive patterns have been supported, it became obvious that species’ responses might be rather specific and may also depend on habitat preferences of the species in question. Distribution of Melitaea ornata, a little known fritillary species is analysed on different time scales using MaxEnt software. Using the results of genitalia morphometry and the predicted potential refugia during the Last Glacial Maximum (LGM), we reconstructed probable re-colonisation routes. We also predicted changes in the potential area for 2080. The present distribution fits well the known occurrence data except for the Iberian Peninsula and North-Africa where the species is missing. Based on our predictions, temperate areas seem to be less suitable for the species. We proposed two hypotheses to explain this pattern: a less probable recent extinction from Iberia and a more supported historical explanation. Predicted distribution during the LGM mainly fits to widely accepted refugia. Europe was probably re-colonised from two main sources, from the Apennine peninsula and from the Balkans which was probably connected to the Anatolian refugia. Populations of the Levant region and in the Elburs Mts. do not show any significant expansion. Further studies are necessary in the case of the predicted Central Asian refugia. Predictions for 2080 show a northward shift and some extinction events in the Mediterranean region. Core areas are identified which might have a potential for expansion including southern Russia, Hungary and possibly Provence in France. Predicted northward area shifts are only possible if the potential leading edge populations and habitats of the species can be preserved.

Nest-site characteristics and breeding density of Magpie Pica pica in Sombor (NW Serbia)

Nest-site characteristics and breeding density of Magpie Pica pica in Sombor (NW Serbia) In March 2009, active Magpie Pica pica nests were censused in the town of Sombor (Vojvodina, NW Serbia) to study nest-site characteristics, breeding density and spatial distribution. The area of the town can be divided into two parts according to different urban landscapes, i.e. the town centre (150 ha) and the residential area (2,224 ha). In total, 222 Magpie nests were found and their height, tree species and nest-site type determined. Nests were found in 25 tree and two shrub species, the most of them (31.1%) being placed in the commonest tree species in the town, the Common Hackberry Celtis occidentalis. The majority of the nests were found in tree avenues (39.6%) and groups of trees (31.5%). Nests in the town centre with a mean height (± SD) of 15.2 ± 4.05 m were significantly higher than those in the residential area with a mean height (± SD) of 11.4 ± 5.13 m. The mean distance of nests from the top of the canopy (± SD) was 1.5 ± 1.33 m, demonstrating the Magpies tendency to place its nests in the very tops of trees in the urban areas. In the residential area, nests were present in every height class, while in the town centre they were not found lower than 5 m. This difference can be explained by denser human population in the town centre and hence greater disturbance (e.g. pedestrians), as found in several other studies, but also by the negative effect of high buildings that prevail there. Thus, the height of surrounding buildings, too, might play an important role in nest-site selection in Magpies breeding in urban habitats, especially in densely built-up areas. Breeding density of Magpie in Sombor was 0.94 pairs/10 ha, with almost twice as high in the town centre as in the residential area. The findings of this study are compared to those obtained in other studies in Serbia and abroad. Značilnosti gnezdišč in gnezditvena gostota srake Pica pica v Somboru (SZ Srbija)

Habitat use and nesting success of the Great Reed Warbler (Acrocephalus arundinaceus) in different reed habitats in Serbia

ABSTRACT 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.

Wing size-related reed habitat selection by Great Reed Warbler (Acrocephalus arundinaceus) males

ABSTRACT In this study we explored the linkage between wing size of Great Reed Warbler males (Acrocephalus arundinaceus) and their habitat selection and relate these linkages to differences in reed habitat quality. We measured the wing sizes of males nesting in 6 different reed habitats. To explain reed habitat selection, we modeled male wing size as a function of 7 predictor variables describing reedbeds: proportion of managed reed; densities of mixed, old, and fresh reed; reed stem diameter; water depth; and fluctuation of water level. Mean wing size was greatest for males at large canals, intermediate at mining ponds and smaller canals, and lowest at marshes and very small canals. The proportion of managed reed and fluctuation of water level were negatively related to wing size, and water depth was positively related to wing size, which suggests that males with larger wings preferred reed habitats with little management in deep water with little fluctuation in water level. We concluded that the availability of stable, deep water and lack of management are primarily important in attracting larger-winged (presumably dominant) males.

Improved land cover mapping using aerial photographs and satellite images

Abstract Manual Land Cover Mapping using aerial photographs provides sufficient level of resolution for detailed vegetation or land cover maps. However, in some cases it is not possible to achieve the desired information over large areas, for example from historical data where the quality and amount of available images is definitely lower than from modern data. The use of automated and semiautomated methods offers the means to identify the vegetation cover using remotely sensed data. In this paper automated methods were tested on aerial photographs and satellite images to extract better and more reliable information about vegetation cover. These testswere performed by using automated analysis of LANDSAT7 images (with and without the surface model of the Shuttle Radar Topography Mission (SRTM)) and two temporally similar aerial photographs. The spectral bands were analyzed with supervised (maximum likelihood) methods. In conclusion, the SRTM and the combination of two temporally similar aerial photographs from earlier years were useful in separating the vegetation cover on a floodplain area. In addition the different date of the vegetation season also gave reliable information about the land cover. High quality information about old and present vegetation on a large area is an essential prerequisites ensuring the conservation of ecosystems

Reed management influences philopatry to reed habitats in the Great Reed Warbler (Acrocephalus arundinaceus)

ABSTRACT Management of reed beds primarily includes controlling water levels and removing vegetation by mowing, burning, or grazing. Although recent studies have demonstrated increased diversity and abundance of wetland specialists after reed bed management, documenting demographic benefits to individual species would add additional support to the advantages of appropriate management. Here, we explore the effects of reed management on the philopatry of Great Reed Warblers (Acrocephalus arundinaceus) over 7 yr. Reed beds were managed in the winter by occasional burning at mining ponds and large canals, infrequent burning in marshes, and frequent mowing of small canals. Based on resightings and recaptures of 1,243 adult and 1,428 nestlings individually marked at 57 sites in 6 different reed habitats, we built Cormack-Jolly-Seber models to estimate the apparent annual survival and encounter probabilities of birds banded as nestlings or as adults. Apparent survival varied in time for both age groups and both sexes, suggesting annual fluctuations in survival, whereas encounter probability remained constant across years. The encounter probability of birds banded as juveniles was higher in reed beds with shallower water. The encounter probability of birds banded as adults was higher in reed beds with deeper water for females, and strongly increased with variation in reed management and less strongly with variation in water depth for males. We also found that the few returning juveniles displayed strong philopatry to the reed habitat occupied in their first breeding season. Our study provides evidence that reed management influences the return rates of juveniles and adult males and females in different ways. Spatially variable reed management by mowing or burning should be applied and water of varying depths should be maintained to maximize return rates of Great Reed Warblers.

Estimation of the mean of multivariate AR processes

In this paper, we show that for autoregressive processes the estimators of mean are consistent if the component of the process is ‘periodical’, and it is not the case if the component is a damping one. In the one-dimensional AR(1) case, the mean cannot be estimated well. In the complex AR(1), where the process behaves periodically, the mean can be estimated well. For an AR(2) process, the mean can be estimated well if the roots of the characteristic equation are complex.

Asymptotic behaviour of the least squares estimator of the mean of AR(1) models

The aim of the paper is to investigate the limit behaviour of the least squares estimator of the shift parameter of nearly unstable, nearly stable, and nearly explosive AR(1) models. Both zero start and stationary cases are treated. Connection with the maximum likelihood estimator of the shift parameter of continuous time AR(1) processes is also discussed.