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Stable isotope analyses can detect interactions between different stages of the annual cycle in migratory animals. We used carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) isotopes to identify non-breeding environments, the strategy of nutrient allocation to eggs, and potential carry-over effects from wintering areas in Red-necked Grebes Podiceps grisegena breeding in eastern Poland. Strongly positive isotopic signatures in adult grebe feathers compared to freshwater food webs and feathers of locally fledged young suggested that most adults had moulted in marine areas. Enriched isotopic values in the breast muscles of spring-arriving grebes pointed to transfer of marine-derived nutrients to freshwater breeding sites. Isotopic mixing models revealed that egg nutrients were mainly acquired locally. Endogenous nutrients were to some extent mobilised for the formation of albumen (25–26%, 95% credible interval, three-isotope model) and lipid-free yolk (17–18%, two-isotope, δ13C and δ15N model) in early laid clutches, but were little mobilised, if at all, in clutches of females that delayed laying. The non-breeding trophic feeding level, as indexed by δ15N in feathers of grebe females, was related to laying initiation date (greater enrichment, earlier egg production), indicating cross–seasonal effects on reproduction. Both endogenous nutrient transfer to eggs and a high-quality non-breeding diet may facilitate early breeding, which is advantageous in species constrained by short breeding seasons. [ABSTRACT FROM AUTHOR]

Summary: From 1995 to 1998 seven cases of prolonged incubation of unhatchable eggs by Red-necked Grebes (Podiceps grisegena) were observed in south east Poland, all of relatively constant duration (34–36 days). The regular occurrence of prolonged incubation can be attributed to low hatchability rates. It is argued that the failure in assessment of the current egg viability is a by-product of excessive nest attendance as a primary adaptation to irregularities in hatching spreads. [ABSTRACT FROM AUTHOR]

Red-necked Grebe (RNG) breeding numbers have been declining in parts of Europe for more than 10 years. We have examined population trends and estimated, for the first time, survival rates of RNGs in a population in eastern Poland in order to explore the mechanisms behind the decline. We counted nesting pairs and recorded breeding success of RNGs nesting on fish ponds. Since 1996 we marked 91 adults and 79 young individually with colour rings and collected resightings of the marked birds. We estimated apparent survival with a Cormack-Jolly-Seber model and used estimates to create a Leslie matrix model for the study population. The population dropped from an estimated 69 breeding pairs in 1995 to a minimum of 12 pairs in 2010, and subsequently remained at 13-16 pairs until 2015. Average annual apparent survival was 0.16 in first-year females and 0.76 in adult females, or 0.18 and 0.79 for sexes pooled, respectively. Site fidelity was high only in adults. Matrix models based on the observed survival rates predicted the observed population decline until 2010. A stable model population was only reached when we increased first-year survival to 0.5. While winter severity had a strong influence on annual survival, low recruitment despite sufficient breeding success was the most important mechanism in this decline. Our observations suggest that natal dispersal, which was not compensated for by immigration, is likely the main proximate mechanism behind the decline. [ABSTRACT FROM AUTHOR]

Knowledge about interactions between habitat quality and individual condition is vital for understanding ecological processes. We examined variation in commonly used hematological indices and body mass in incubating and chick-rearing Red-necked Grebes (Podiceps grisegena) in Poland breeding under contrasting foraging conditions in ponds used for aquaculture. Grebes used either ponds with low prey availability in the early breeding period and abundant food in the brood-rearing stage (high-quality habitat), or ponds stocked with fish attractive as prey to spring-arriving adults yet later unavailable to chicks due to size constraints (low-quality habitat acting as an ecological trap). Parental effort, measured as the proportion of time allocated to food acquisition and provisioning of chicks, was greater in the low-quality habitat, although adult grebes spent less time foraging there than in the high-quality habitat early in the season. Scaled body mass was higher in incubating grebes than in brood-rearing grebes, regardless of habitat quality. Breeding stage by habitat interactions were significant for hemoglobin, erythrocyte count (RBC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH), with greater MCV and MCH values (by 20-34%, on average) during brood-rearing than during incubation in the low-quality habitat, and the opposite pattern (by 15-16%) in the high-quality habitat. These hematological responses signify changes in physiological stress associated with parental workloads. Higher MCV and MCH levels (by 22-31%) during the chick-rearing stage in the low-quality compared with the high-quality habitat indicate that parents incurred physiological costs of breeding under ecological trap conditions. No significant effects were found on leucocyte indices (total leucocyte count and heterophil/lymphocyte ratio). We consider the hemoglobin- and RBC-related parameters to be promising indicators of habitat-driven stress associated with prolonged physical exertion, especially when multiple metrics are employed. [ABSTRACT FROM AUTHOR]

Patterns of louse infestation in waterbirds deserve attention due to potential impacts on host populations. Red-necked Grebes ( Podiceps grisegena) were visually examined for the presence of amblyceran chewing lice during the 2000-2015 breeding seasons in eastern Poland. Only one species of lice ( Pseudomenopon dolium) was recorded. Amblyceran prevalence was low; four young birds (2.7%) were found infested out of 147 banded individuals (66 adults and 81 chicks). However, all infested Red-necked Grebes bore heavy parasite loads. Negative consequences of infestation for physiological condition were indicated by low hemoglobin and total protein values when compared with same-age non-infested birds. The low infestation rate can be related to the biology of the host (a diving species undergoing molt at sea, solitary breeder) and the apparent high pathogenicity of P. dolium, which left numerous holes in feathers and bleeding bites in all parasitized birds. [ABSTRACT FROM AUTHOR]

To identify optimal habitat for the Aquatic Warbler Acrocephalus paludicola, a flagship species of fen mires, we related numbers of singing males to habitat variables in all core breeding sites in eastern Poland. The density of male Aquatic Warblers increased with increasing ground cover by water and mosses and litter layer height, and was highest where vegetation was 60-90 cm tall. Male densities also increased with the biomass of arthropods > 10 mm length, estimated by sweep netting, and with the abundance of spiders, estimated by pan trapping. We suggest that habitat management should take into account species-specific morphological adaptations, nest safety and arthropod productivity. Prevention of vegetation succession is a conservation priority for open fen mires. However, modern management practices to achieve this, especially mowing using tracked vehicles, should be evaluated and optimized to ensure that such practices do not adversely affect the long-term development of moss cover and litter structure. [ABSTRACT FROM AUTHOR]

Wildlife occurring at aquacultural sites can ignite conflicts over resources managed by humans. A telephone survey concerning nuisance wildlife occurrence, perceptions of inflicted damage, and use of preventive measures at pond fisheries was conducted in 2003-2004 in eastern Poland. Significant economic losses to wildlife were reported by 80% of the respondents, with 41% claiming severe losses to more than one species. Serious damage was attributed primarily to otters Lutra lutra (56% of farms), cormorants Phalacrocorax carbo (26%), grey herons Ardea cinerea (23%), and beavers Castor fiber (21%). Two alien species, mink Neovison vison and muskrat Ondatra zibethicus, were widespread, but rarely blamed for causing substantial harm. Lethal controls were the most popular means of damage reduction and were more likely to be deployed at fish farms reporting significant losses. Cormorants, shot at half of the farms visited, were the most widely persecuted. Both otters and beavers were culled, notwithstanding their protection status and compensation payments available for beaver damage to ponds. The survey indicated poor cooperation between conservation authorities and fish farmers in managing wildlife concerns. Monitoring conflict interactions, i.e., wildlife occurrence and alleged damage at fish farms vs damage management processes, is an essential step toward conflict alleviation. Considering the wide range of species interacting with fisheries, adoption of more flexible policies to address the conflicts than a single-species conservation approach is recommended. [ABSTRACT FROM AUTHOR]