Zbigniew Kasprzykowski

Micro-habitat nest preferences of the great bittern, Botaurus stellaris, on fishponds in central-eastern Poland

The nest-site requirements of the great bittern Botaurus stellaris females in relation to habitat availability were studied in 2003–2006 at fish-pond complexes located in the Lublin and Podlasie regions (eastern Poland). The structure of emergent vegetation and water depth were measured and described in 230 control squares and 98 squares with occupied nests. Water depth, vegetation cover, the height and diameter of reed shoots, the number of flowering shoots, the density of old (dry) and new (green) reed shoots were measured. Great bittern females nested in all available types of emergent vegetation and most of the nests were located in reedbeds. Using the logistic regression model it was shown that when choosing the place for nesting the great bitterns preferred reedbeds with a high density of old-reed stems.

Metal interactions within and between tissues of nestling rooks Corvus frugilegus

We analyzed interactions of concentrations of 11 essential and nonessential elements, including toxic metals within and between internal organs (liver, kidney and lung), muscles and bones of nestling rooks Corvus frugilegus with acute cadmium contamination and elevated level of lead. The number of statistically significant (P ≤ 0.05) metal-metal relationships (positive/negative) within particular tissues was the highest in the kidney (7/6), following in the bone (9/2), liver (6/4), lung (5/2) and muscle (5/2). We found eight significant interactions of lead with other metals, and only two of cadmium (only with lead and cobalt, which probably mirrored a greater ability of lead (than in the case of cadmium) to functional and kinetic interaction with other metals, and/or inhibiting effect of lead or cadmium in co-accumulation. Furthermore, a positive relationship between concentration of cadmium and lead in the kidney could hint at the key importance of this organ in detoxification of both toxic metals. Analyses of relationships of individual metals between examined tissues show only positive results in the case of copper (n = 8), following potassium (n = 3), zinc and iron (in both cases n = 2) and a single ones for calcium and magnesium. We concluded that the lack of significant relationships of individual toxic metals (cadmium or lead) between analyzed tissues could result from high levels of these metals, which destroyed detoxifying capacity of kidney, and ultimately enabled a rapid bioaccumulation of these inorganic contaminations in all tissues of examined nestlings. An explanation of concentration of toxic metals in tissues of animals, especially in the case of their high level, require an identification of the actual level of essential elements associated with physiological status of organism.

Residues of chromium, nickel, cadmium and lead in Rook Corvus frugilegus eggshells from urban and rural areas of Poland.

We examined the concentrations of chromium (Cr), nickel (Ni), cadmium (Cd) and lead (Pb) in Rook Corvus frugilegus eggshells from 43 rookeries situated in rural and urban areas of western (=intensive agriculture) and eastern (=extensive agriculture) Poland. We found small ranges in the overall level of Cr (the difference between the extreme values was 1.8-fold; range of concentrations=5.21-9.40 Cr ppm), Ni (3.5-fold; 1.15-4.07 Ni ppm), and Cd (2.6-fold; 0.34-0.91 Cd ppm), whereas concentrations of Pb varied markedly, i.e. 6.7-fold between extreme values (1.71-11.53 Pb ppm). Eggshell levels of these four elements did not differ between rural rookeries from western and eastern Poland, but eggshells from rookeries in large/industrial cities had significantly higher concentrations of Cr, Ni and Pb than those from small towns and villages. Our study suggests that female Rooks exhibited an apparent variation in the intensity of trace metal bioaccumulation in their eggshells, that rapid site-dependent bioaccumulation of Cu, Cr, Ni and Pb occurs as a result of the pollution gradient (rural<urban), and that Cd levels are probably regulated physiologically, even though these were relatively high, which could be treated as an overall proxy of a heavy Cd load in the soil environment.

The effect of weather conditions on the breeding biology of the Eurasian Bittern Botaurus stellaris in eastern Poland

Numerous studies carried out on different bird species have shown that weather conditions can modify their breeding biology at various stages in their reproduction. Directly or indirectly, meteorological factors can affect breeding success by modifying brood survival and the availability of food resources. The present study examined the relationships between weather conditions and selected breeding parameters in the Eurasian Bittern. It was carried out in 2003–2009 on extensively farmed carp ponds located in eastern Poland. With the aid of multiple regression models, we analysed the effect of the mean ambient temperature, mean daily temperature range, mean daily minimum temperature, total precipitation and mean wind speed on the number of eggs in a clutch, egg size, and partial losses of eggs and chicks. A significant adverse relationship between the sum of rainfall in the laying period and the mean egg volume in a clutch was found. Greater mortality among young Eurasian Bitterns was also correlated with strong rains and winds during the chick-rearing period. There were two critical periods in the population we studied – before the first egg was laid, and the chick-rearing period – which were particularly sensitive to changes in the weather.

Nest location within the tree and breeding parameters of Rooks Corvus frugilegus

Capsule The position of a nest in the tree influences some parameters of reproduction. Aim To determine breeding parameters in relation to the spatial distribution of nests in trees. Methods In 2000–02 a total of 177 Rook nests were studied in seven colonies situated in eastern Poland. Breeding parameters of Rooks were compared between vertical and horizontal zones of the tree canopy. Results The vertical distribution of Rook nests in trees affected the number of hatchlings and, after eliminating a variable describing horizontal distribution, also the clutch size. The horizontal distribution of nests, their number in a vertical zone or in a tree did not affect breeding parameters. Differences in laying dates of the first eggs between vertical zones were not statistically significant. In the lowest zone (C) both mean clutch size and mean number of hatchlings were significantly lower than those in the highest vertical zone (A) and the middle zone (B). Breeding success was higher in zones A and B, while the greatest losses during incubation and feeding of nestlings were observed in zone C. However, the numbers of fledglings in the smaller proportion of nests in zone C that did produce young were similar to the numbers in nests in zones A and B. Therefore, differences between the zones in the numbers of fledglings were not significant. Conclusion Rook nests in the top zone of the tree canopy have larger clutch sizes and numbers of hatchlings at the beginning of the nesting cycle. However, in spite of the clearly lower values of these parameters and higher total losses in broods in the lowest zone, the number of fledglings was similar in all zones.

Habitat preferences of granivorous passerine birds wintering on farmland in eastern Poland

Capsule Fallow land, manure heaps and stubble were the most important habitats for birds wintering in low-intensity farmland in eastern Poland. Aims To describe habitat types and to determine the preferences of granivorous passerines in open farmland in eastern Poland. Methods Small passerines were counted along ten 1-km-long transects in three seasons from 2003 to 2006 in open, strongly fragmented farmland in eastern Poland. Results Birds were recorded in eight habitat types of different significance for particular species. More than 50% of individuals and the highest number of species were recorded on stubble and fallow land. The glm model showed the influence of fallow areas and the presence of the other habitats on bird species numbers. The preference index was significantly higher for manure heaps than for other habitats. Conclusion The open agricultural landscape in eastern Poland provides attractive habitats for wintering granivorous birds, such as stubble and fallow land. These birds also use the manure heaps that are a feature of traditional, low-intensity farmland.

The significance of cereal stubble and manure heaps for birds wintering in the farmland of eastern Poland

Summary. The presence of wintering birds on manure and stubble was studied in the open farmland of eastern Poland. Among the 34 species recorded during transect surveys, 13 were on manure heaps and 16 in stubble fields. Species diversity did not differ significantly between these habitats but there were differences in the densities of individuals. Snow depth had a positive influence on the birds observed on manure heaps but had a negative impact on those associated with stubble. Logistic regression analysis showed that birds selected manure heaps with larger surface areas and larger areas of fresh manure, but that the duration of manure heaps did not affect their choices. This habitat can be used as an alternative food source and roosting site during long-lasting snow cover. This has been particularly important for the yellowhammer Emberiza citrinella, whose Polish breeding population is one of the largest in Europe.

Effects of Weather Conditions, Time of Breeding, Brood Size and Hatching Order on Eurasian Bittern Nestling Growth in a Food-Rich Fishpond Habitat

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.

Reproduction Parameters of the Great Bittern Botaurus stellaris in the Fish Ponds of Eastern Poland

Abstract. Reproduction of the Great Bittern Botaurus stellaris was studied in fishponds in eastern Poland from 2003 to 2009. Study areas were surveyed from March to early July, and the booming period of the Great Bittern was from March to July, varying between 58 to 108 days. The start of booming activity was linked to climatic factors. We visited 143 active nests in the study population, with the majority of females starting to lay eggs at the end of April to the beginning of May. The mean clutch size was 4.8 ± 0.8 (n = 109, range 1–6). There was no significant difference in clutch size between years or within years as the season progressed. Hatching success was high 92% (n = 78 broods). For all years of the study the breeding success (measured as a proportion of successful broods to all broods) was 51% (n = 120). The mean number of fledglings (15-days old chicks) per breeding female was 1.5 (SD ± 1.7, n = 116) and the mean number of fledglings per successful female was 3.0 (SD ± 1.2, n = 58). The main mortality factor for eggs and nestlings was mammalian predation. The high breeding parameters obtained for this population were probably due to extensive fish management and the good and stable food resources in the fishponds surveyed. Long-term monitoring and study of the population structure and breeding parameters of the Great Bittern in relation to known environmental factors are an essential tool for the conservation and management plans for this threatened species.

Relationships between stomach content and concentrations of essential and non-essential elements in tissues of omnivorous nestling rooks Corvus frugilegus: Is the size and composition of stomach content relevant?

Abstract. Soil-invertebrate feeding birds can be exposed to high doses of toxic metals through their diet. Recently, we have shown that nestling rooks Corvus frugilegus from several rookeries in Poland have a cadmium (Cd) tissue level diagnostic for acute contamination as well as an elevated level of lead (Pb). To explain the potential pathway of bioaccumulation of 11 essential and non-essential elements, including two metals of primary concern (Cd and Pb), in target tissues of these nestlings, we analyzed the relationships between the dietary characteristics of stomach content (mass of digesta, number of cereal grains, plant and animal items, and grit particles) and concentrations of these elements determined in the liver, kidneys, lung, muscles and bones. Our analysis showed in total 17 (8 negative and 9 positive) statistically significant relationships between the five analyzed dietary characteristics of stomach content and concentrations of metals in the liver, kidneys, muscles and bone. We found a significant positive relationship between the number of animal food items and Cd-level in kidneys; and a negative relationship between the number of plant items and Pb-level in the liver, and between the number of grit particles and Pb-level in kidneys. Despite the limitations of our study due to the different degree of digestion of some food items, our findings suggest high bioavailability of Cd from animal food items and a low level or reduced gastrointestinal absorption of Pb from plant food (mainly cereals). We urge further research on absorption of Cd and Pb from different dietary components and application of diet analysis to explain the complex nature of bioaccumulation of anthropogenic contaminants in the internal organs and tissues of birds and other species of animals, especially in species with a mixed plant-animal diet.