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Relatively little information exists on the effects of mercury on terrestrial wildlife populations. We analyzed 38 free-living small rodent females (Myodes glareolus, Microtus agrestris, and Apodemus flavicolis), of which 11 were pregnant, for total mercury concentrations in combined liver and kidney samples. Using a single-purpose atomic absorption spectrometer for mercury determination, the measured mercury values ranged from 0.006 to 0.079 mg/kg. Pregnant females had significantly (P<0.041) higher mercury levels in liver and kidney than did nonpregnant females. Our results suggest that during mercury biomonitoring studies it is necessary to consider the pregnancy of the analyzed animals. [ABSTRACT FROM AUTHOR]

Vocal activity is one of the main attributes that enables assessment of the presence and abundance of animal populations. However, the factors affecting vocal activity are rarely studied, especially in owls. We studied the vocal activity of Boreal Owl (Aegolius funereus) using acoustic monitoring in relation to environmental factors in Central Europe (Czech Republic), over an area of 100 km². We analysed a total of 1,310 hours of sound recordings collected over two years (2015 and 2016) at the turn of March/April and April/May. The frequency of sampling points in which we recorded Boreal Owl vocalizations varied from 0.17 to 0.59 and was higher in the year of increased prey abundance(2015) and earlier in the breeding season (March/April). The duration of Boreal Owl vocal activity varied from 1 to 60 minutes per hour and was related to temporal factors. In particular, the duration of Boreal Owl vocalization increased late in the breeding season (April/May) and in the year of higher prey abundance (2015), and it showed two peaks of vocal activity during the night. Weather conditions, the occurrence of nesting Boreal Owl pairs, and the vocalization of other owl species had no effect on the duration of Boreal Owl vocalization. These findings highlight the importance of between-year, seasonal, and within-night variability in the Boreal Owl vocal activity and document that acoustic monitoring based on sound recorders works well for monitoring of nocturnal bird species. [ABSTRACT FROM AUTHOR]

Genetic methods enable to reveal cryptic parental contributions in reproduction, especially in socially monogamous species. The rate of extra-pair paternity is generally low in raptors and owls and its presence in some species is tightly associated with sequential polyandry which can rarely occur in years with high food availability. In this study we investigated the mating system of the Tengmalm's owl (Aegolius funereus) in the Ore Mountains (Czech Republic). In this area, the species usually nests in high breeding densities which could increase an opportunity for extra-pair copulations. In total, 297 individuals (54 females, 47 males and 196 juveniles) from 46 nest boxes were genotyped at seven microsatellite loci. We present results of a five-year study and four extra-pair nestlings (2.3 %) were detected which did not result from sequential polyandry. [ABSTRACT FROM AUTHOR]

Camera recording and video analysis have emerged as a successful non-invasive method for collecting a wide range of biological data on many different taxa of animals. However, camera monitoring has rarely been applied to long-term surveillance of cavity or box-nesting species and ordinary off-the-shelf cameras are employed., We present methodology and data on the effectiveness of nest box monitoring using a camera system embedded in four 'smart nest boxes' ( SNBoxes). We applied the SNBoxes to eight Tengmalm's owl ( Aegolius funereus) nests in the Czech Republic during a 5-month period in 2014. Each SNBox consisted of a pair of cameras with infrared lighting, an event detector, a radiofrequency identification reader, auxiliary sensors and a 60 Ah 12 V battery to power the whole system. All devices used were centrally managed by an embedded computer with specifically developed software., Using four SNBoxes, we observed owl nesting continually during the incubation, nestling and fledgling phases, in total 309 days, resulting in 3382 owl video events. Batteries were changed every 6·5 days. A memory of 4 GB was found sufficient to store monthly data. We identified 12 types of male and female parental activities and their timing, the diet composition and frequency of prey delivery, the manner of prey storage, the light intensity at the time of each parental activity, the temperature inside the clutch and outside the box and the duration of nestling period of each young. We also produced a video on owl nesting for the general public., The SNBox and related methodology show enormous potential as a non-invasive tool for monitoring animals using boxes or natural cavities. The main advantage of the SNBox is the possibility to study both nocturnal and diurnal animal species and great flexibility in use of the software and hardware for different tasks. As a result, the SNBox provides an opportunity for novel insights into the breeding, roosting, hibernating, and food storage activities of a wide range of cavity-living birds, mammals and reptiles. [ABSTRACT FROM AUTHOR]

Environmental variation across space and time can strongly influence life-history strategies in vertebrates. It has been shown that the reproductive success of birds of prey is closely related to food availability. However, relatively little is known about intraspecific differences in reproductive success of birds in relation to varying ecological conditions across environmental gradients. We investigated the reproductive performance of Tengmalm's Owls Aegolius funereus in a temperate (Czech Republic, 50°N) and a boreal (Finland, 63°N) population in relation to long-term variations in the abundance of their main prey (small rodents). Prey densities at the northern site were much higher, but there were also large inter-annual fluctuations and years with steep summer declines of vole densities. Northern owls laid larger clutches but offspring production per nest was similar at both study sites. This resulted from higher nestling mortality in the northern population, especially in nests established later in the season. Despite much greater nesting losses due to predation by Pine Martens Martes martes, productivity at the population level was about four times greater at the temperate site, mainly due to the much higher breeding densities compared with Finland. Tengmalm's Owls at the temperate study site may benefit from relatively stable prey abundance, a more diverse prey community that offers alternative prey during vole scarcity, longer nights in summer that allow more time for foraging, and a lower level of interspecific competition with other vole-specialized predators. [ABSTRACT FROM AUTHOR]

The behaviour of the nestlings of nocturnal cavity-nesting species has relatively rarely been studied in detail because of problems connected with use of the technical devices required to provide long-term monitoring of individuals. However, long-term observation of nestling behaviour is crucial in order to identify different types of behaviour which may be caused by sibling competition at the end of nesting period. We studied behaviour of 43 Tengmalm's owl (Aegolius funereus) nestlings at 14 nests using a camera and a chip system. The nestlings perched at the nest box entrance from an average age of 28 days from hatching (range 24–34 days) until fledging, spending around 2 hours per day here in total, in periods ranging from a few seconds to 147 min (7.6±10.9 min, mean ± SD). We found that individual duration of perching at the nest box entrance was significantly influenced by nestlings' age and wing length and that the duration of perching at the nest box entrance significantly decreased with time of night. However, during daylight hours, time of day had no effect on either probability or duration of nestlings' perching. We suggest daylight perching at the nest box entrance results from nestlings' preparation for fledging, while individuals perching here during the night may gain an advantageous position for obtaining food from the parents; another possibility at all times of day is that nestlings can reaffirm their social dominance status by monopolizing the nest box entrance. [ABSTRACT FROM AUTHOR]

The article assesses the diet composition of Tengmalm's Owls during the breeding season by means of a combination of pellet analysis and camera recordings. Data suggests that the diet of the owls is comprised of voles, mice and shrews, and that their proportion in the diet reflected their local abundances in the field. It speculates that the underestimation of voles may have been a result of their decapitation before delivery to the nest. It notes that the effectiveness of determining prey species to higher taxa was higher for camera monitoring than pellet analyses. It recommends the use of both methods for a more accurate assessment of diet composition of breeding raptors and owls.

The article offers information concerning a study which examines the effects of food abundance, reproductive success and age of nestlings on parental care in female Tengmalm's Owls. Result shows that food abundance and reproductive success were higher in 2004 than in 2006 in the Ore Mountains, Czech Republic. It notes that reproductive success of owls was correlated with both the total number of prey items and the proportional contribution of the females to nestling feeding. Researchers concluded if the ecological conditions are such that the offspring can be raised by a single parent, its mate may abandon the clutch or brood and increase its fitness by sequential polygamy during a single breeding season.

The article presents a study which investigated whether the males of the Tengmalm's owl change their activity patterns under varying food conditions in the Czech Republic. During two breeding seasons, 12 owl nests were continuously monitored by a camera system to collect data on the time of male prey delivery and identification of prey items brought to nestlings. Although the abundance of food supply differed in both years, there was no difference in the number of prey items delivered by males to their nests. It concludes that the results of the study suggest that activity patterns of Tengmalm's owl males in Central Europe do not depend on varying food conditions.