Impacts of grazing,selective logging and hyper‐aggressors on diurnal bird fauna in intact forest landscapes of the Brigalow Belt,Queensland

The impact of forest management on diurnal bird assemblages and abundance was investigated in contiguous tracts of eucalypt forest in the Brigalow Belt Bioregion, south central Queensland. Sites were located across three levels of livestock grazing intensity and three levels of selective logging intensity within the most extensive habitat type, Corymbia citriodora‐dominant forest. We recorded a high rate of incidence and large numbers of the hyper‐aggressive noisy miner Manorina melanocephala (Passeriformes: Meliphagidae) at the majority of our survey sites, a phenomenon rarely reported in non‐cleared landscapes. As shown by numerous studies in fragmented landscapes, the distribution of this species in our study had a substantial negative effect upon the distribution of small passerine species. Noisy miners exerted the strongest influence upon small passerine abundance, and masked any forest management effects. However, key habitat features important for small passerines were identified, including a relatively high density of large trees and stems in the midstorey. Selective logging appeared to exert a minimal effect upon noisy miner abundance, whereas grazing intensity had a profound, positive influence. Noisy miners were most abundant in intensively grazed forest with minimal midstorey and a low volume of coarse woody debris. Higher road density in the forest landscape also corresponded with increased numbers of noisy miners. Reduction in grazing pressure in Brigalow Belt forests has the potential to benefit small passerine assemblages across large areas through moderating noisy miner abundance. The strong relationship between noisy miners and small passerines suggests that noisy miner abundance could act as an easily measured indicator of forest condition, potentially contributing to monitoring of forest management outcomes.     

Environmental pollution affects genetic diversity in wild bird populations

Many common environmental pollutants, together with nuclear radiation, are recognized as genotoxic. There is, however, very little information on pollution-related genetic effects on free-living animal populations, especially in terrestrial ecosystems. We investigated whether genetic diversity in two small insectivorous passerines, the great tit (Parus major) and the pied flycatcher (Ficedula hypoleuca), was changed near point sources of heavy metals (two copper smelters) or radioactive isotopes (nuclear material reprocessing plant). We measured concentration of heavy metals and nucleotide diversity in mitochondrial DNA in feather samples taken from nestlings in multiple polluted areas and at control sites. In both species, heavy metal concentrations - especially of arsenic - were increased in feathers collected at smelter sites. The P. major population living near a smelter showed significantly higher nucleotide diversity than a control population in an unpolluted site, suggesting increased mutation rates in a polluted environment. On the contrary, F. hypoleuca showed reduced nucleotide diversity at both smelter sites but increased nucleotide diversity near the source of radioactivity. Our results show that heavy metal pollution and low level nuclear radiation affect the nucleotide diversity in two free-living insectivorous passerines. We suggest that the different response in these two species may be due to their different ability to handle toxic compounds in the body.     

Variations of Abundance and Community Structure of Ammonia Oxidizers and Nitrification Activity in Two Paddy Soils Polluted by Heavy Metals

While microbial nitrogen transformations are sensitive indicators of trace metal toxicity in soils, studies that quantify the impacts of heavy metal pollution in polluted rice soils on microbial communities and their activities remain limited. We examined changes in the abundance, composition and activity of ammonia oxidizing communities in two paddy fields that have been polluted by metal mining and smelting activities for more than three decades. The results showed a shift in the community structure of ammonia oxidizing archaea (AOA) and, to a lesser extent, of ammonia oxidizing bacteria (AOB) under metal pollution in the soils. All the retrieved AOB sequences in this study belonged to the genus Nitrosospira. Among them, the species in Cluster 3 a.1 seemed to be more sensitive to heavy metal pollution. Both AOB abundance and nitrification activity were not affected by heavy metal pollution in the two sites; whereas, AOA abundance increased. Our results suggested an effect of metal pollutants on communities of ammonia oxidizers, the degree of which varied in accordance with the amount of metal pollution. Therefore, it is difficult to quantify the relationship between the AOB/AOA communities and nitrification activity in the polluted soil.     

Growth and mortality of nestling great tits (Parus major) and pied flycatchers (Ficedula hypoleuca) in a heavy metal pollution gradient

We studied nestling growth, growth abnormalities, mortality and breeding success of two hole-nesting passerines, the great tit (Parus major) and the pied fly-catcher (Ficedula hypoleuca), at 14 study sites around a copper smelter complex in Harjavalta, south-west Finland in 1991–1993. The main pollutants in the area are heavy metals and sulphuric oxides. Exposure of birds to heavy metals was shown by measuring their faecal concentrations. Copper, nickel and lead contents of nestling faeces were high near the factory and decreased with distance away from the pollution source. F. hypoleuca nestlings suffered high mortality very close to the factory complex, but did relatively well at all other sites. Breeding success of P. major was below background levels up to 3–4 km from the pollution source and nestlings grew poorly close to the factory. Growth abnormalities of legs and wings in F. hypoleuca nestlings were significantly more common near the factory than farther away. In contrast, F. hypoleuca nestlings grew equally well at all distances. The poor breeding success of F. hypoleuca close to the factory complex is probably related to the high amount of heavy metals in its diet, and low availability of calcium-rich food items may enhance this effect. We suggest that the poor breeding success of P. major is related to habitat changes that have taken place around the factory. The different responses of these two bird species are probably due to their different diet. Our results show convincingly that species-specific differences in response should be carefully considered when planning schemes for air pollution monitoring.     

三峡库区磷化工厂点源污染对陆生植物群落组成和物种多样性的影响

2006年4月中旬至6月下旬, 采用典型取样法, 在三峡库区某磷化工厂周围污染源区与对照区设置样方, 进行常规群落学调查, 分析点源污染对陆生植物群落种类组成以及物种多样性的影响。结果表明: (1) 所有样方中共计出现284种植物, 其中乔木35种, 灌木139种, 草本110种。仅在污染区中出现的物种数量远低于仅在对照区中出现的物种数量; (2) 可分出4种基本的群落类型: 马尾松(Pinus massoniana)林、柏木(Cupressus funepris)林、栓皮栎(Quercus variabilis)林和马尾松+栓皮栎林, 各群落特定层次的物种丰富度指数以及Pielou均匀度指数在污染区与对照区之间存在显著差异; (3)污染胁迫下, 物种在群落中的生态优势度发生了变化, 反映了群落中不同物种相互替代的过程, 这种物种的替代可为今后受损生态系统人为恢复过程中物种的筛选提供一定的理论参考; (4)对群落中主要物种更新的调查发现: 栓皮栎林对污染不敏感; 柏木林污染区与对照区幼苗数量及分布格局均有明显差异, 污染条件下群落未来演替受到严重干扰。综上所述, 我们可以看出, 在点源污染影响下, 群落的组成和结构发生了显著变化, 但这种变化对群落的长期影响仍需要进一步的深入研究。     

Do miners (Manorina spp.) affect bird assemblages in continuous savanna woodlands in north‐eastern Australia?

Overabundant native species can have a significant cascading effect on other components of wildlife, and those that deplete other species, often promoted by anthropogenic change to vegetation cover and habitat, are called reverse keystone species. Birds in the genus Manorina are widely reported as being such species, and in highly disturbed or fragmented environments, and some intact environments, noisy miners Manorina melanocephala can have a strong negative effect on small passerine species via hyper‐aggressive mobbing. The tropical savannas of northern Australia consist of largely unmodified woodlands, and two species of Manorina occur naturally in this region: the noisy miner and the yellow‐throated miner Manorina flavigula. Therefore, what effect do these species have on bird assemblage in predominantly continuous habitats, relative to other typical determinants of avifauna assemblage such as vegetation structure? We used data collected from bird surveys at 511 sites across northern Queensland (179 noisy miner M. melanocephala sites, 332 yellow‐throated miner M. flavigula sites) between 1998 and 2010. We examined the variation in bird composition at each site due to increasing abundance of Manorina spp. using uni‐ and multivariate techniques. We found total bird richness was significantly lower in sites where noisy and yellow‐throated miner abundances were highest, and passerine species seemed most affected. For species, 45 species varied significantly in abundance with increasing miner numbers, and the overall effect of yellow‐throated miners on other birds seemed more pronounced. However, vegetation structure was generally an equal or more important predictor of avifauna richness and abundance. We conclude that despite the superficially intact nature of northern Australian woodlands, pastoral intensification or poor land management might create disturbances that facilitate increases in the abundance of Manorina, causing localized overabundance and a compounding negative effect on other native bird species.     

Numerical and functional responses of breeding passerine species to mass occurrence of geometrid caterpillars in a subalpine birch forest: a 30-year study

In northern Fennoscandia, the geometrid moths Epirrita autumnata and Operophtera brumata have cyclicities in density with mass occurrence at 10‐year intervals. The larvae of Epirrita and Operophtera attain a size of 2–3 cm and 1.5–2 cm, respectively, and are nutritious food items for passerine birds. To examine whether these larvae have any numerical and/or functional influence on a passerine bird community (mountain birch forest in Budal, central Norway) during a 30‐year period (1972–2001), I estimated their abundance (number of larvae per 100 sweeps) in the birch canopy, and the densities of breeding birds in the passerine community. In addition, from 1972 to 1998, I monitored the nesting success of five of the bird species. The foraging pattern of the most abundant bird species and their gizzard contents (adults and nestlings) were examined in 1972–78 (covering population peaks of both the geometrids). Population peaks of Epirrita occurred in 1975–76, 1985–86 and 1996, and of Operophtera in 1976–77, 1986–87 and 1997–98. The passerine community consisted of eight species that were territorial in all 30 years, one species in 26 years, three species in 14–21 years and three species in 1–4 years. Only the Brambling Fringilla montifringilla population responded numerically to the fluctuations of Epirrita and Operophtera. Brambling was also the only species whose mean clutch size varied between years, and this correlated positively with the density of Epirrita. The mean annual nesting success of Willow Warbler Phylloscopus trochilus, Bluethroat Luscinia svecica and Common Redpoll Carduelis flammea tended to be higher in years with mass outbreaks of Epirrita, but was significantly so only for Reed Bunting Emberiza schoeniclus. The abundance of Operophtera larvae showed no influence on the nesting success of any bird species. The passerines foraged more frequently in the birch canopy in the Epirrita outbreak years (1975–76) than in the years before or after. Gizzard analyses of five adult passerine species and their nestlings showed that Epirrita was the main food item in 1974–76. Even though Operophtera occurred in large numbers in birch trees in 1976 and 1977, only a few larvae were found in the gizzards of the passerines. None of the passerines showed an increase in their population density in the year following the larval outbreaks, but the densities of Willow Warbler and Bluethroat increased in the succeeding year, indicating a higher return rate for these species. The study shows the existence of a dietary response and also indicates a reproductive response to the changes in the abundance of Epirrita in mountain birch forest. The lack of numerical response in the passerines (except the Brambling) to the fluctuation in Epirrita contrasts with the pattern described for passerine communities in northern temperate deciduous forests in North America, where Lepidoptera caterpillars periodically have mass outbreaks.     

Breeding biology of the Cattle Egret Bubulcus ibis in southwest Spain

The ecology of passerines using saltmarshes in winter is poorly known. The distribution and abundance of passerines on the Taff/Ely saltmarshes were studied between October 1983 and March 1984. Twenty-two species of passerine were recorded. Their numbers fluctuated irregularly throughout the winter. The four most abundant species, Skylark, Chaffinch, Meadow Pipit and Reed Bunting, showed preferences for certain plant communities. Skylarks shifted from the Asteretum community to Spartinetum, and Chaffinches from the Asteretum to a mixed-species community as winter progressed. Faecal analysis showed that both species consumed seeds from similar plants but took them in different proportions.     

Abundance,Composition and Activity of Ammonia Oxidizer and Denitrifier Communities in Metal Polluted Rice Paddies from South China

While microbial nitrogen transformations in soils had been known to be affected by heavy metal pollution, changes in abundance and community structure of the mediating microbial populations had been not yet well characterized in polluted rice soils. Here, by using the prevailing molecular fingerprinting and enzyme activity assays and comparisons to adjacent non-polluted soils, we examined changes in the abundance and activity of ammonia oxidizing and denitrifying communities of rice paddies in two sites with different metal accumulation situation under long-term pollution from metal mining and smelter activities. Potential nitrifying activity was significantly reduced in polluted paddies in both sites while potential denitrifying activity reduced only in the soils with high Cu accumulation up to 1300 mg kg⁻¹. Copy numbers of amoA (AOA and AOB genes) were lower in both polluted paddies, following the trend with the enzyme assays, whereas that of nirK was not significantly affected. Analysis of the DGGE profiles revealed a shift in the community structure of AOA, and to a lesser extent, differences in the community structure of AOB and denitrifier between soils from the two sites with different pollution intensity and metal composition. All of the retrieved AOB sequences belonged to the genus Nitrosospira, among which species Cluster 4 appeared more sensitive to metal pollution. In contrast, nirK genes were widely distributed among different bacterial genera that were represented differentially between the polluted and unpolluted paddies. This could suggest either a possible non-specific target of the primers conventionally used in soil study or complex interactions between soil properties and metal contents on the observed community and activity changes, and thus on the N transformation in the polluted rice soils.     

Responses of arthropods to plant diversity: changes after pollution cessation

Data collected from three different polluted sites in the vicinity of a phosphate fertilizer factory that was closed in 1990 are used to test with Mantel tests and smoothing techniques whether the rapid increase of plant species richness following cessation of pollution enhanced associated arthropod assemblage diversity. 132 plant species (between 1990 and 1999) and 66 413 individuals of 680 arthropod species (using sweep net sampling between 1990 and 1996) were recorded. Using top soil pH as a representative pollution parameter we detected an increase of plant species richness, effective diversity and evenness of plant community with decreasing pH both in space and time. While the richness of all studied functional groups of herbivores increased with plant species richness, only the richness of one carnivore functional group showed a similar pattern. Plant species richness was significantly correlated to the abundance patterns of two herbivore and two carnivore groups. But contrary to theoretical predictions consumer abundance tended to decrease with increasing plant diversity only between a plant species richness range of 10 to ca 35. Our results support the findings of previous studies that highlight how increased plant species and functional group richness may result in higher herbivore species richness, and that carnivore richness may be influenced by herbivore and detritivore richness. The functional group approach used in this study has enabled us to detected the very individual interaction patterns that occur between different groups within the same trophic level.     

Ant predation ofEriocrania miners in a polluted area

We tested the hypothesis that air pollution may affect population densities of birch-feeding leafminers via changes in ant predation. Foraging activity of three ant species (Formica rufa, F. fusca andF. lemani), predation rates and population densities of both solitary and gregariousEriocrania (Lepidoptera: Eriocraniidae) miners were investigated at 13 sites around the Harjavalta copper-nickel smelter, SW Finland. Ant species differed in their distribution patterns relative to pollution. However, the total percentage of birch trees foraged by ants (all species combined) showed no correlation with the distance from the factory complex. As a result, no clear trends in predation rates were apparent in relation to the distance from the pollution source for either solitary or gregariousEriocrania species. Densities of the solitaryEriocrania species tended to increase with the distance from the pollution source whereas densities of the gregariousE. haworthi peaked close to the factory complex. No corresponding differences in predation rates between solitary and gregarious miners were found. Ant predation, thus, did not explain density patterns ofEriocrania miners in the polluted area.     

Distribution and behaviour of passerines around Peregrine Falco peregrinus eyries in western Greenland

This paper describes the distribution and behaviour of passerine birds within 1 km of Peregrine Falcon Falco peregrinus eyries in western Greenland. Passerine populations were censused in 1983 around six cliffs occupied by nesting Peregrines and at six sites on the open tundra, and in 1984 at two unoccupied sites suitable for Peregrine nesting.
Four passerine species accounted for over 90% of birds seen. Within 400 m of Peregrine occupied cliffs, three species, Lapland Longspur Calcarius lapponicus . Northern Wheatear Oenanthe oenanthe , and Common Redpoll Carduelisflammea , were found in lower than average abundance while the fourth, Snow Bunting Plectrophenax nivalis , was found in increased abundance. Our indirect tests suggest that Peregrine presence, rather than direct predation, was responsible for the distributions of the first three species. The Snow Bunting, however, behaviourally adapts to Peregrine presence in order to exploit nesting habitat available at the cliff base.
These results contrast strongly with those reported by other Arctic workers, where increased abundances of potential prey were observed in close proximity to nesting Peregrines.     

Management of reedbeds: mosaic reed cutting does not affect prey abundance and nest predation rate of reed passerine birds

Reed passerine birds are strict habitat specialists inhabiting reedbed habitats. In Europe, many of these species are threatened due to loss and degradation of natural reedbeds. Another important factor that can negatively affect the abundance of reed passerines is commercial reed harvesting. Previous studies have shown negative impacts of large-scale winter reed cutting on passerine breeding assemblages and arthropod communities. The effect of reed cutting on a small scale, however, has not been studied experimentally to date. The aim of this study was to investigate whether and how small-scale, mosaic reed cutting influences prey abundance and nest predation rate of reed passerines. In June, after the reed had reached maturity, we conducted nest predation experiments with artificial nests and arthropod sampling using pan traps in cut reed patches, adjacent uncut reed patches and unmanaged reedbed. We found no differences in the risk of egg predation between three types of reedbeds. In contrast, the abundance of arthropods in cut and adjacent uncut reed patches was significantly higher than that in unmanaged reedbed. We assume this was caused by habitat heterogeneity, small size of cut patches and their rapid recolonization by arthropods from adjacent uncut patches. Our results suggest that in contrast to large-scale reed cutting, small-scale, mosaic reed cutting has no negative effect on nest survival and food abundance of reed passerine birds. However, given that we performed all experiments in June, i.e., when the reed was mature, our findings cannot be generalized to whole breeding period of all reed passerine birds. Therefore, temporal variation in nest predation rate and arthropod abundance in managed and unmanaged reedbeds during the entire breeding season should be examined in future studies.     

Seasonal variation in the abundance, biomass and biodiversity of earthworms in soils contaminated with metal emissions from a primary smelting works

1. Earthworms (Annelida: Oligochaeta) were sampled on four occasions (spring, summer, autumn and winter) at 14 sites along two transects from a primary lead/ zinc/cadmium smelting works at Avonmouth, UK.
2. Total abundance and biomass of earthworms decreased with proximity to the smelter. No worms were collected from the two sites closest to the factory (<0·6 km) and catches were significantly lower than controls at a further five sites (<3 km).
3. Seasonal composition of sampled communities differed only for summer with lower numbers of individuals and species collected at all sites. Reduced catches in the summer sample is a response to drought.
4. Species richness was lowest at sites close to the factory. For example, worms such as Aporrectodea caliginosa (Savigny) and Allolobophora chlorotica (Savigny) that were dominant at relatively clean sites further from the smelter are absent from the most contaminated soils.
5. Reduced species richness resulted in lower Shannon–Weiner diversity and higher Berger–Parker dominance. Multivariate cluster analysis for spring, summer and winter indicated that sites could be split into three groups based upon relative species composition. In autumn, two clusters were identified.
6. The absence of sensitive species from sites close to the smelting works supports the inclusion of earthworms as a key group in a terrestrial prediction and classification scheme for quantifying the effects of pollutants on soil biodiversity. However, sampling should be carried out in spring or autumn to obtain an accurate picture of community structure.     

Soil macroinvertebrates as indicators of pollution by heavy metals

A broad range of soil pollutants were found to decrease with distance from a zinc smelter from 35,000 to 77, 8270 to 40 and from 190 to less than 1 ppm for zinc, lead and cadmium, respectively. Along this gradient, observed species richness of soil macro-organisms seemed to be more affected by the land-use type than by soil pollution--minimum in crops (21), maximum in woody sites (126). IndVal index allowed isolation of 21 indicator species from the 339 morphospecies identified. Most of these indicator species were characteristic of the unpolluted sites: only two diplopods and one gastropod from polluted poplar plantations, and none from the most polluted site. Since soil invertebrates respond to different environmental factors, including direct effect of heavy metals, we suggest there may be some confounding factors generating spurious relationships between the values of species as bioindicators and the pollution status they are supposed to indicate.     

Variations of body mass and immune function in response to food unpredictability in magpies

The effects of food unpredictability on body mass regulation have been studied in a few species of birds. It has been shown that small passerines can counteract variability of food resources by actively regulating their body reserves through an increase of mass. However, it was recently found that, with unpredictable food availability, quails and hooded crows do not adopt an adaptive fattening strategy but lose mass. At present, little is known about the effects of food unpredictability on other body parameters, such as immune functions and blood variables. In this study, we analysed the responses to food abundance and unpredictability by performing two experiments of controlled food administration in the magpie, a passerine intermediate in size between small passerines and crows. Body mass, leukocyte abundance, haematocrit, spleen mass and immune reaction to phytohaemagglutinin (PHA) were assessed during a 15-d period. In the first experiment, the food release was predictable (same amount each day), but the quantity of food varied in four groups of birds. Low food levels induced a greater decrease in mass. In the second experiment, the same average quantity of food was supplied, but with predictable or unpredictable (random) schedules. As previously reported for crows and quails, magpies did not adaptively increase their mass in response to food unpredictability. Furthermore, there was a decrease of haematocrit and immune response to PHA. It appears that a body mass decrease in the magpie can be induced by a reduction of either food abundance or food predictability, and it is accompanied by a worsening of health state.     

The role of mobile consumers in lake nutrient cycles: a brief review

Spawning habitats of anchovy Engraulis encrasicolus and sardinella Sardinella aurita were investigated in the Gulf of Gabès by means of two surveys carried out during the summer of 2005 and 2009. The spatial patterns of early developmental stages were analyzed through Lloyd’s patchiness index, single quotient analyses, and principal component analyses. The results showed that Gulf of Gabès is an important area for anchovy and sardinella spawning. Within this area, anchovy and sardinella showed preference for the warmest waters to spawn. The main spawning areas for anchovy were located in the inner parts of the Gulf, and a secondary spawning area was observed offshore. Contrastingly, the main spawning ground of sardinella was found in the center of the Gulf. In both years, early larvae of anchovy showed a greater degree of aggregation than that of sardinella. The developmental stages of both species showed low spatial overlap, indicating that the spawning habitats of these species are spatially differentiated in the Gulf of Gabès.     

Duplication of accelerated evolution and growth hormone gene in passerine birds

We report the discovery of a duplication of the growth hormone (GH) gene in a major group of birds, the passerines (Aves: Passeriformes). Phylogenetic analysis of 1.3-kb partial DNA sequences of GH genes for 24 species of passerines and numerous outgroups indicates that the duplication occurred in the ancestral lineage of extant passerines. Both duplicates and their open-reading frames are preserved throughout the passerine clade, and both duplicates are expressed in the zebra finch brain, suggesting that both are likely to be functional. The estimated rates of amino acid evolution are more than 10-fold higher in passerine GH genes than in those of their closest nonpasserine relatives. In addition, although the 84 codons sequenced are generally highly conserved for both passerines and nonpasserines, comparisons of the nonsynonymous/synonymous substitution ratios and the rate of predicted amino acid changes indicate that the 2 gene duplicates are evolving under different selective pressures and may be functionally divergent. The evidence of differential selection, coupled with the preservation of both gene copies in all major lineages since the origin of passerines, suggests that the duplication may be of adaptive significance, with possible implications for the explosive diversification of the passerine clade.     

Distribution-abundance relationship for passerines breeding in Tunisian oases: test of the sampling hypothesis

The positive relationship between local abundance and distribution of species is a widely recognized pattern in community ecology. However, it has been suggested that this relationship can simply be an artefact of sampling because locally rare species are less detectable then locally abundant ones, and hence their distribution can easily be underestimated. Here, we use count data to investigate the relationship between distribution and abundance of passerines breeding in a sample of oases from southern Tunisia, and we provide a test of the sampling artefact hypothesis. In particular, we checked for a difference in detection probability between localized and widespread species, and we tested if increasing the sampling effort affects the significance of the relationship. A significant positive relationship between the average local abundance of passerine species and the proportion of occupied oases was found. The use of a capture-recapture approach allowed us to estimate and to compare the detection probabilities of localized and widespread species subsets. We found that localized species were locally less detectable than widespread species, which is consistent with the main assumption of the sampling artefact hypothesis. However, increasing the detection probability of species by conducting more counts did not affect the significance of the relationship, which did not give support to the sampling artefact hypothesis. Our work implies that sampling contributed to the distribution-abundance relationship we found, but that it is unlikely that such a relationship could entirely be explained by an artefact of sampling. It also underlines the insight that can be gained by using probabilistic approaches of estimating species number and detection probability when attempting to disentangle sampling from ecological effects in community ecology studies.     

Higher nest predation risk in association with a top predator: mesopredator attraction?

Breeding close to top predators is a widespread reproductive strategy. Breeding animals may gain indirect benefits if proximity to top predators results in a reduction of predation due to suppression of mesopredators. We tested if passerine birds gain protection from mesopredators by nesting within territories of a top predator, the Ural owl (Strix uralensis). We placed nest boxes for pied flycatchers (Ficedula hypoleuca) in Ural owl nest sites and in control sites (currently unoccupied by owls). The nest boxes were designed so that nest predation risk could be altered (experimentally increased) after flycatcher settlement; we considered predation rate as a proxy of mesopredator abundance. Overall, we found higher nest predation rates in treatment than in control sites. Flycatcher laying date did not differ between sites, but smaller clutches were laid in treatment sites compared to controls, suggesting a response to perceived predation risk. Relative nest predation rate varied between years, being higher in owl nest sites in 2 years but similar in another; this variation might be indirectly influenced by vole abundance. Proximity to Ural owl nests might represent a risky habitat for passerines. High predation rates within owl territories could be because small mesopredators that do not directly threaten owl nests are attracted to owl nest sites. This could be explained if some mesopredators use owl territories to gain protection from their own predators, or if top predators and mesopredators independently seek similar habitats.