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The recovery of some predator species in recent decades has intensified conflicts between humans and predators. To mitigate these conflicts, knowledge of predator-prey relationships is needed. The aim of this study was to estimate the predation rate of common buzzards Buteo buteo on young brown hares Lepus europaeus and to compare the magnitude of this predation between two areas that differ in the type of agricultural landscape, i.e. the size of crop fields. In the years 2005–2014, the composition of buzzard diet was studied in western Poland by analysing pellets and prey remains of nestlings and adult birds (7971 prey items identified) and estimating the abundance of buzzards (searching for and observing their nests) and hares (spotlight counts) in two adjacent areas (75 km2 in total) with small and large fields. The diet of common buzzards was dominated by common voles Microtus arvalis, and the frequency of hares ranged from 1.1% of prey items in the nestling diet to 0.2% in the diet of post-breeding individuals. The total number of hares consumed by buzzards during the spring-summer season in the whole study area amounted to 2.94 per km2, which is equal to 7.8–15.3% of the young hares born per km2. However, the predation rate estimated based on the nestling food was 2.6 times lower in small fields than in large fields. Thus, this study suggests that reducing buzzard predation on young hares can be achieved by habitat management, i.e. the creation of agricultural landscapes with numerous field boundaries. [ABSTRACT FROM AUTHOR]

The increasing number of roads is an important threat to living organisms on a global scale, although research describing the influence of roads on the immune response of birds is lacking. The main purpose of this study was to examine the effect of distance from the road on the chicks' immune function. The research was conducted in the Krzyszkowice Forest near Krakow (S Poland) in spring 2012. Two common bird species: Great Tit and Eurasian Blue Tit bred in new nest boxes installed on trees with various distances from the road. In half of the nests, adult females were challenged with the antigen sheep red blood cells (SRBC) to check whether this experiment and the neighbourhood of road - both potentially lowering the immune response of nestlings - together cause an interactive effect. Nestling immune response was measured by the phytohaemagglutinin (PHA) skin-testing technique. Nestlings in nest boxes closer to the road showed a weaker reaction to PHA than those farther away. This effect was, however, noticed only in Great Tits' nests where the breeding female was not immune challenged. In both species, chicks raised by SRBC-challenged females had a low immune response irrespective of road distance. This research is the first one showing the relationship between indirect maternal effect, distance from the road and nestling immune response differing in two species. [ABSTRACT FROM AUTHOR]

Several types of rare behaviour patterns occurring during the post-fledging period were observed in young Marsh Harriers (Circus aeruginosus L.; Aves, Accipitridae). The studies were carried out in natural and anthropogenic habitats in Eastern Poland. Out of 23 monitored nests, 17 individually wing-tagged fledglings from 6 broods were observed during the post-fledging period. We observed cases of kleptoparasitism between fledglings and adults, siblings, and unrelated young birds. Some of them were unsuccessful trials to steal prey. Moreover, mutual roosting of young from different nests was noticed. Intruding birds roosted together with local fledglings for up to 150 minutes. Kleptoparasitism and mutual roosting have been rarely observed in raptors before. We discussed the role of this behaviour in the context of increasing the independence of fledglings and the ability to recognize offsprings by adult birds. [ABSTRACT FROM AUTHOR]

Haematological indices have been frequently used to investigate the physiological condition of wild birds. In this respect, among many blood parameters, haematocrit has been considered to be a valuable indicator. Many studies, mostly conducted on adult birds, have discussed possible causes of haematocrit variation, pointing out several factors both natural and anthropogenic as being crucial. In this study, we examined the level of haematocrit for Blue Tit Cyanistes caeruleus nestlings in relation to habitat type and inter-year sources of variation. We found that the haematocrit of Blue Tit nestlings varied significantly between study years, showing an increasing trend. We explain this variation by changeable weather conditions, pointing out that temperature is a possible factor. The increase in haematocrit in subsequent study years was accompanied by a decline in the ambient temperature. No significant effect of habitat type was noted in the haematocrit variation. We also found that haematocrit values tended to be positively associated with fledging success. All this confirms that haematocrit may be reasonably used as a one of the indicators of nestling condition. [ABSTRACT FROM AUTHOR]

Several studies have previously proposed that blood hemoglobin concentration in nestling passerines is a reliable index of individual condition and nutritional state. In this paper we present results concerning variation in hemoglobin concentration in the blood of ca. 14-day-old nestling great tits Parus major in central Poland in an 11-year-long period, 2003–2013, in two distinct habitat types: urban park and deciduous forest. The most important findings of the study were: (i) variation in hemoglobin concentration was consistent within broods, (ii) hemoglobin concentration of nestlings varied markedly across years, (iii) hemoglobin concentration was significantly higher in the forest study site which is richer in terms of food abundance during the short period of tits breeding season and (iv) high hemoglobin level was a predictor of nestling survival from hatching to fledging. [ABSTRACT FROM AUTHOR]

The development of nestlings depends on both biological and weather factors. However, their combined effect differs among bird species. In this study, the impacts of three temperature variables, precipitation, wind speed, timing of breeding, brood size and hatching order on the growth of Eurasian bittern Botaurus stellaris chicks were analysed. Measurements of 183 nestlings from 57 nests were made at fishpond complexes in eastern Poland. Relative growth rates (RGR) were calculated on the basis of tarsus length and body mass. Generalised linear mixed models showed that brood size, hatching order and precipitation were the most important factors. Nestlings in broods of two and three grew faster than those from broods of four and five. In the largest broods, the fifth-hatched chicks had lower growth rates; this also applied to the oldest chicks in all brood-size categories. Nestlings from late-season nests showed enhanced mass and tarsus growth, while heavier precipitation and strong winds depressed growth rates. The study emphasises that even among bitterns breeding in food-rich habitats like fishponds, the chicks in largest broods run the risk of lower growth rates. [ABSTRACT FROM AUTHOR]

In this study, we examined heavy-metal concentrations in feathers of nestling great tits Parus major and blue tits Cyanistes caeruleus at two different sites (urban parkland vs. deciduous forest) located in the Łódź agglomeration in relation to interyear variation. We found that tit species did not differ significantly in lead and cadmium concentrations. Zinc concentration was significantly higher in blue tits. We also found that lead and cadmium levels in blue tit nestlings and the level of lead in great tit nestlings were higher in the parkland site than in the woodland site. We explain habitat variation in heavy-metal concentrations in feathers of nestlings by different levels of contamination at study sites. For both tit species, significant variation in heavy-metal amounts accumulated by nestlings was found between years with the lowest value in a year with the lowest value of rainfall. We suggest that the interyear variation may be accounted for by differences in rainfall, thus influencing quantities of trace elements bioavailable in the environment. [ABSTRACT FROM AUTHOR]

In most of colonial avian species, central parts of the colonies offer higher safety in terms of predatory pressure. However, in heterogeneous habitats, nest sites of high physical quality are likely to offer effective protection against predators or adverse weather conditions regardless of their location within the colony. The aim of this paper was to investigate whether nest site selection in a tree-nesting waterbird, the Great Cormorant Phalacrocorax carbo sinensis, depends on the within-colony location of sites, their physical quality or a combination of these components. The study was conducted during 2010-2011 in a cormorant colony in central Poland. We found that early-breeding individuals preferred nest sites in the central parts of the colony and located high off the ground. The high quality of pairs nesting in these locations was confirmed with good body condition of nestlings, measured by their body masses and plasma concentrations of glucose and urea. A similar spatial pattern was found for the daily nest survival rate and reproductive success. It was found that the central nesting sites associated with high nesting densities were better protected against predators, while the physical quality of nesting sites determined the probability of nest collapse before the conclusion of breeding activities. The two-way process of assessing nest site attractiveness (nest site location vs. physical quality) suggests that, under the limitation of the most attractive nesting sites (good-quality central sites), tree-nesting waterbirds may trade central nesting locations for the high-quality sites at the peripheries of the colony. [ABSTRACT FROM AUTHOR]

Altricial birds nesting in places with a favourable microclimate would be able to maintain the proper temperature of eggs or nestlings with less effort and thus reproduce more successfully. Tree cavities provide relatively safe nesting sites, but their microclimate is hardly known. Here we present the first data on air temperature and humidity in natural cavities used by Great Tits nesting in protected primeval forest in the Białowie a National Park (Eastern Poland). We checked what microclimatic conditions existed in cavities selected by Great Tits, how the construction of a nest changed the microclimate in a cavity and to what extent cavity localisation and cavity dimensions modified the microclimate of the breeding cavities. Great Tits used cavities in the living trees which were characterised by cool but relatively stable temperatures and very high relative humidity. Such conditions appear to be typical for cavities in living trees in general. Cavities with Great Tit broods were warmer and drier that the unused ones. The microclimate did not appear to constitute the major factor determining Great Tit usage of cavities in living trees, but it could exert a modifying effect on the pattern of cavity use by them. By choosing cavities of appropriate dimensions and placing the nest at an appropriate distance from the entrance, Great Tits could modify the cavity microclimate. However, their options were probably constrained by necessity to meet other important requirements, such as nest safety and illumination. [ABSTRACT FROM AUTHOR]

Concentration of minerals (sodium, potassium, calcium [Ca], magnesium, iron [Fe], copper, zinc [Zn], manganese [Mn], and cobalt) as well as toxic metals (cadmium [Cd], lead [Pb]) were determined in five tissues (liver, lung, kidney, muscle, and bone) of nestling rooks ( Corvus frugilegus; 1 to 13 days old) found dead in seven breeding colonies in eastern Poland. Cd concentration in all analyzed tissues was in the narrow range of 17.0-17.2 mg/kg dry weight (dw) Cd, which in the light of the literature data indicates acute contamination by this toxic metal. Similarly, we found increased levels of Pb, which in all tissues ranged between 5.0 and 6.2 mg/kg dw. Results of multivariate general linear model (GLM) testing of the effect of three variables (tissue type, colony, and nestling age) on tissue concentrations of various metals showed significance for Fe, Cu, Zn, and Mn. Only concentrations of Ca, Fe, and Zn differed significantly between the analyzed tissues. GLM analysis did not show any statistically significant differences in tissue levels of minerals and both toxic metals among examined rookeries, which indicates the widespread presence of nonpoint Cd and Pb pollution linked to agricultural activity and similar levels of these inorganic contaminants on crop fields (feeding grounds) around breeding colonies. We concluded that high levels of both toxic metals, Cd and Pb, probably resulting from the diet of nestling rooks, are based mainly on a diet of ground-dwelling beetles gathered on crop fields. [ABSTRACT FROM AUTHOR]

The article presents a study on the weak correlation between the hematocrit and hemoglobin concentration of nestling Blue Tits Parus caeruleus and Great Tits P. major. The researchers performed the study during the breeding season of 2010 as part of a long-term research project on the breeding biology of tits in Poland. They also used intra-class correlations to calculate within-brood repeatability. They found a significant positive correlation between hematocrit value and hemoglobin concentration for the nestlings of both species.

The article presents the conducted study on the sex-specific nestling-feeding behavior of the parents of the red-breasted flycatcher, Ficedula parva. In the study carried out in the Bialowieza National Park in Poland, a generalised linear mixed model (GLMM) was employed to estimate the nestling-feeding frequency and relative feeding effort based on the sex of the parents and the age and number of nestlings. Based on the study, the age of the nestlings is the main predictor in determining the feeding frequency of the parents.

The article presents a study which analyzes the stomach contents of dead Rook Corvus frugilegus nestlings at several breeding colonies in Poland, and the relation of their weight to the number of minerals plants and food items found in their stomachs. It explains that determination of food composition is important in conservation efforts for a species since food is important in the determination of size and distribution of rookeries. Collected nestlings were weighed before the food items in their stomach were identified and divided into animal, plant and mineral categories. Results reveal that the stomach contents of the nestlings are composed of 46.5% animals, 12.2% plants, and 41.2% mineral, and that the larvae of Coleoptera are the most common prey of the nestlings.

This article deals with a study which investigated the influence of ambient temperature, variation in ambient temperature and rainfall on the breeding performance of the red-backed shrike Lanius collurio in eastern Poland. The study site was an 855-hectare (ha) agricultural landscape. Multiple regression method was adopted in this study to analyse the influence of weather conditions on breeding performance. Results of the study showed that there were large differences in the variance of ambient temperature and total rainfall between subsequent clutches. The study also cited 0.4 eggs per clutch as the mean size of losses between the number of fertile eggs laid and the number of hatched nestlings.

The breeding performance of the Red-backed Shrike ( Lanius collurio) in relation to the territory characteristics was investigated. The study was conducted in an area of high agricultural land use, characterised by small field size, a more mosaic habitat and low use of mineral fertilisers in comparison to Western European countries. The influence of habitat structure and composition in the territory on the date of clutch initiation, nest predation and clutch size in the Red-backed Shrike was not found, but such an influence on the number of nestlings was shown. The minimum adequate model explained 18.3% of the variation between territories in nestling’s number. The number of fledglings was positively correlated with the area of pastures, meadows, orchards and fallows within territories, and negatively correlated with length of overhead transmission lines. The number of fledglings was correlated with food abundance within territories, based on to the results from pitfall traps. There was no correlation between territory food abundance and the size of clutch. The presence of pastures, meadows and fallows, which are foraging places, thus seems to be crucial for the protection of the Red-backed Shrike. [ABSTRACT FROM AUTHOR]

We looked for evidence of a cost of reproduction in the Marsh Tit Parus palustris living in the last fragments of primeval temperate forest (Białowieża National Park, eastern Poland). Potential nest-holes were superabundant but the birds had to cope with a diverse set of predators, dangerous both to broods and to parents. Taking advantage of the natural variation in realized reproductive investment that this caused in terms of the loss of nests or mates, we expected to find differences in survival and future fecundity between birds which had lost broods (reduced effort), had reared young (controls) or were either provisioning young single-handed or had laid replacement clutches (increased effort). Despite 13 years of observation, even during seasons with very strenuous conditions, we have failed to demonstrate that the observed range of variation in parental investment caused any demographic cost of reproduction. Incubating females were regularly killed on the nest, which could indicate the existence of a cost operating in the earlier stages of the breeding cycle. Overall, these results suggest that the reproductive rate in Marsh Tits is not controlled proximately by reproductive cost. [ABSTRACT FROM AUTHOR]

The effectiveness of tartar emetic in causing forced regurgitation was tested in hooded crow ( Corvus corone cornix) nestlings from a protected area in western Poland. Tartar emetic was highly effective in causing regurgitation. In 84 of 98 cases (85.7%), nestlings responded by vomiting reflexes, producing 81 food samples (82.6% of all cases). After the procedure no bird was observed to develop negative symptoms. Survival of the birds subjected to forced regurgitation was higher than in the control group (no emetic), which is probably related to the administration of glucose to the birds after enforced regurgitation. Even repeated administration of tartar emetic was without negative effects on the nestlings. The use of tartar emetic does not require frequent visits at the nests, limiting the probability of cannibalistic behaviour and nest predation. [ABSTRACT FROM AUTHOR]