Thomas Oliver Mérő

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.

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.

Factors influencing the appearance of spider (Araneae) and beetle (Coleoptera) assemblages in nests of great reed warbler Acrocephalus arundinaceus

The appearance of spider (Araneae) and beetle (Coleoptera) assemblages found in nests of great reed warbler Acrocephalus arundinaceus was studied, firstly to investigate breeding success and the amount of precipitation as potential factors which might affect the abundance and species richness of both groups. In addition, we compared the diversity of spider and beetle assemblages between nests found in different reed habitats, and considered the position of nests (above water or dry ground). In this study we selected five different randomly chosen reed habitats: two mining ponds, two small canals and one large canal. Great Reed Warbler nests were collected either shortly after fledging, or after the clutch had failed. Altogether, 12 species of spider and 19 species of beetle were collected. In both groups there was no significant difference in abundance between successful, lost and cuckoo-parasitized nests; however, there was a significant difference in species richness between the three nest categories in spider assemblages, which was not the case in beetle assemblages. The amount of precipitation did not affect beetle or spider abundance; only the species richness of spiders showed significant growth. Furthermore, we found no significant relationship between vegetation cover and the species richness and abundance of spiders and beetles. The diversity of both groups differed significantly according to reed habitat: beetle assemblages were most diverse by the large canal and spiders at the mining ponds.

Unusual Fishing Behavior of the Eurasian Sparrowhawk (Accipiter nisus)

The Eurasian Sparrowhawk (Accipiter nisus; hereafter sparrowhawk) is a generalist predator (Quinn and Cresswell 2004), feeding primarily on birds (over 90% of prey items in most studies; Newton 1986, Zawadzka and Zawadzki 2001, Bujoczek and Ciach 2009). Sparrowhawks occur frequently in human-altered landscapes, including residential areas, where some individuals overwinter (e.g., McGrady 1991, Mér} o and Žuljević 2010). Hunting success can be higher at low temperatures, and lower when precipitation is present and the wind is strong (Hilton et al. 1999, Quinn and Cresswell 2004). Under unfavorable conditions, sparrowhawks can alternatively consume other small prey, such as small mammals (Tomešek and Čermák 2009). We here report on unusual prey selection and hunting behavior of the sparrowhawk. Our observation took place in Debrecen (462 km), the third largest city in Hungary, where the sparrowhawk is one of the most common raptors (Bozsko and Juhász 1985). During a walk in the Botanical Garden of the University of Debrecen (47833.49N, 21837.29E, 126 masl) on 18 January 2017, we spotted a subadult (2 yr old; SY) sparrowhawk engaged in several short, quick, low flights above the nonfrozen part of a koi (Cyprinus carpio haematopterus) pond (water garden). These apparent predation attempts on koi usually started with hovering flight similar to that of the Eurasian Kestrel (Falco tinnunculus), followed by quick, sharp turns as if in pursuit of a fish, followed by immersion of the sparrowhawk’s feet into the water (Fig. 1). Each predation attempt took up to several seconds. Resting time between predation attempts lasted about 3 min while the sparrowhawk stood on the edge of the ice, intently watching the water. The bird always rested on the opposite side of the previous resting point. While the sparrowhawk was ‘‘fishing,’’ we approached from 20 m to 4 m so that we could take better photographs. Although the sparrowhawk noticed us immediately, it continued its activity, and made a total of 15 unsuccessful attempts before being disturbed by a man walking near the pond. To our knowledge, no such fishing behavior has previously been reported for the sparrowhawk. The part of the koi pond where this sparrowhawk attempted to fish was not frozen because of a water circulation system in constant operation, and perhaps because of feeding activity of Mallards (Anas platyrhynchos). Our observation started at 0950 H and lasted until 1045 H. The weather was clear and sunny with mild gusts of wind; the temperature was 18C and the relative humidity was 61% (both measured at 2 m above the ground). The average daily temperature had been consistently below 08C since mid-December, and the average depth of snow cover had been approximately 4 cm since late December. We suggest three possible explanations for the fishing behavior of this sparrowhawk. First, the most common fish species in the koi pond were goldfish (Carassius auratus auratus) and koi. Swimming slowly near the surface, white, orange, or red koi may appear to be easy prey. Aquarists have reported that avian predators such as herons and kingfishers easily catch koi or goldfish (Stickley 1990). The garish coloration and slow swimming of koi and goldfish near the surface might have attracted the sparrowhawk. A second possible explanation might be the prolonged presence of snow cover that year. Our previous experience observing and trapping sparrowhawks suggests that avian prey may more easily detect a hunting sparrowhawk against a white background (snow cover) than against other background colors. This may reduce hunting success in winter, prompting sparrowhawks to hunt alternative prey. A third explanation may be related to the age of the observed sparrowhawk. Prey such as the slowly swimming, garishly colored koi may trigger innovative hunting attempts among subadult and inexperienced, but motivated individuals. 1 Email address: mester.bela@okologia.mta.hu

The effects of reed density, surface and management on the probability of cuckoo (Cuculus canorus) parasitism on great reed warbler (Acrocephalus arundinaceus) nests

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.

Negative effect of roosting starlings (Sturnus vulgaris) on clutch survival in the great reed warbler (Acrocephalus arundinaceus)

Abstract This study provides preliminary findings related to whether and how the roosting of starlings (Sturnus vulgaris) in reedbeds influences the survival of clutches of the great reed warbler (Acrocephalus arundinaceus). During the nesting seasons of 2014 and 2015, we surveyed the complete area of a mining pond in Serbia (south-eastern Europe) for great reed warbler nests, and the presence of roosting starlings was also recorded. Using the Mayfield method, we estimated the daily survival rate of great reed warbler eggs and nestlings, and compared these rates between starling roosting and non-roosting areas. Although both egg and nestling survival rates were lower in the Starling roosting than in the non-roosting areas, the differences were not significant, which was also reflected in overall nesting success. However, when only data from the time period when starling roosting occurred, the overall great reed warbler egg survival was significantly lower in roosting areas than in non-roosting areas. Our results suggest that Starling roosting did not influence the clutch survival of the great reed warbler significantly, but that there can be a negative short-term or local effect. Our study implies that a larger number of starlings and a longer roosting period could affect clutch survival more negatively.

The proportion of cropland influences negatively the occurrence of breeding birds in an alkali grassland habitat in NW Serbia

Abstract Grasslands host a high diversity of plant and animal species. In Serbia, most alkali grasslands are located in the province of Vojvodina. The majority are not subject to conservation. The aim of the study was to investigate the relationship between the proportion of croplands and (1) the number of breeding species and (2) the number of breeding pairs in the alkali grasslands of the upper Mostonga River catchment basin (NW Serbia). The size of the study area was 400 ha. Birds were surveyed along seven parallel transects eight times per breeding season. Lengths of the cross sections of both grasslands and croplands were measured. The proportion of croplands per transect was calculated by dividing the total length of cross sections of croplands by the total length of transect. The relationship between the proportion of croplands and the number of breeding pairs and the number of breeding species, respectively, was studied using simple linear regression. We recorded a total of 171 nesting pairs belonging to 23 species in the alkali grassland investigated, with breeding densities between 2.2 and 10.3 pairs per 10 ha. The number of species per transect ranged between 6 and 11. The most abundant species were Skylark Alauda arvensis, Yellow Wagtail Motacilla flava and Corn Bunting Emberiza calandra. The numbers of breeding pairs (F6 = 21.761, P < 0.0001) and of breeding species (F6 = 13.758, P = 0.001) were both influenced negatively by the proportion of croplands. These findings highlight the need for coordinated conservation measures on the alkali grasslands of Vojvodina.

Latitudinal, longitudinal and weather-related variation in breeding parameters of Great Reed Warblers in Europe: A meta-analysis

Capsule Clutch initiation date decreased with longitude, clutch size increased with latitude and decreased with maximum temperature, whereas the number of fledglings increased both with latitude and longitude, and decreased with maximum temperature in 19 European studies of the Great Reed Warbler. Our study confirmed previous findings about the increasing trend in clutch size with latitude, but also found earlier clutch initiation dates and higher number of fledglings longitudinally from west to east, with precipitation closely associated with clutch initiation date and maximum temperature closely associated with the number of fledglings.

Breeding birds of shelterbelts near Sombor (NW Serbia)

Breeding birds of shelterbelts near Sombor (NW Serbia) In 2008, breeding birds were studied in the shelterbelts surrounded by arable land NW of Sombor (Vojvodina, NW Serbia). Seven 500 m long sections of wooded shelterbelts were selected and surveyed for birds six times between May and July. Sampling plots differed in tree species composition and dominance, in height of trees, and presence and composition of shrub and herb layers. 22 breeding species were found with a mean density of 9.86 ± 1.47 pairs/km of shelterbelt. The mean number of species per shelterbelt was 8.3 ± 1.2. Species richness ranged from 4 (shelterbelt G) to 14 (shelterbelt D) species. Similarity, measured by the Sørensen index, showed strong qualitative similarity (over 70%) between the compared communities in only 19% of all possible pairs of shelterbelts. The most abundant breeding species were Golden Oriole Oriolus oriolus and Greenfinch Carduelis chloris, with overall linear densities of 2.9 and 2.6 pairs/km, respectively. Overall linear densities of a further four species (Red-backed Shrike Lanius collurio, Syrian Woodpecker Dendrocopos syriacus, Whitethroat Sylvia communis and Cuckoo Cuculus canorus) exceeded 1 pair/km. The densities of breeding birds are compared to those obtained during other studies in Europe and elsewhere. Gnezdilke drevoredov pri Somboru (SZ Srbija)