The aim of this study was to determine the possibility of using feathers of blue tit nestlings to assess the level of endogenous accumulation of lead. For this purpose we conducted an experiment with lead application to randomly chosen nestlings from eight randomly drawn broods. Five days after the exposure, feathers of lead-treated nestlings had significantly higher lead concentrations than control nestlings. This result suggests that feathers can be used as reliable non-destructive bioindicators to assess the level of heavy metals originating from contaminated food, which is of great significance for comparative studies on ecological consequences of pollution.

Environmental factors affecting trophic conditions act as stressors on nestling altricial birds. Access of parental birds to a sufficient supply of food in a limited period of the nestling stage differ in time and space, depending on nesting habitat, prey density and weather conditions. Heterophil-to-lymphocyte ratio (H/L) is considered as a reliable indicator of prolonged stress reaction in birds. In this study we examine if variation in H/L shows consistent spatio-temporal patterns in nestlings of two parids, blue tit Cyanistes caeruleus and great tit Parus major. We found that blue tit nestlings had on average higher H/L than great tit nestlings, which corresponds with the ecological sensitivity of these species. In both species H/L was higher in a poor parkland habitat than in a high quality forest habitat. In nestling blue tits, higher H/L values occurred in years characterized by more extreme weather conditions and worse caterpillar availability. Such consistent patterns of variation in the H/L ratio of nestling blue tits and great tits suggest that, when age-dependent effects are controlled, the ratio can be used as an indicator of physiological stress that is generated by food-related stressors differing in space and time. In particular, elevated H/L ratios are indicative of human-induced changes in the structure of breeding habitats.

Integration of landscape ecology and conservation physiology has been recommended as a potentially useful way to investigate consequences of human-induced changes in habitats for animal populations. A central goal of this paper was to examine if a simple physiological parameter displays any consistent patterns of spatio-temporal variation. Blood glucose concentration in birds reflects their high metabolic demands and may be influenced by a number of environmental factors. Therefore we present results concerning variation in glucose concentration in the blood of c. 14-day-old nestling blue tits (Cyanistes caeruleus) in central Poland in an 8-year period, 2005–2012, in two landscapes: an urban parkland and a deciduous forest. The most important findings of the study were: (1) mean levels of blood glucose varied markedly among years, most probably due to variable weather conditions, (2) glucose concentrations were significantly higher in the parkland study site than in the forest site, (3) heavier nestlings had lower glucose levels, and (4) high glucose levels were negatively correlated with fledging and breeding success. Thus we have confirmed that a consistent spatio-temporal pattern really exists.

Summary. Numerous studies from different locations in Europe show that nest-box populations of tits in urban areas lay earlier and produce fewer eggs than do tits in rural areas. We collected data on laying dates and clutch size in two great tit Parus major populations nesting in oak deciduous forest and urban parkland areas, only about 10 km apart, in central Poland over 11 years. The abundance of caterpillars, the optimal food of breeding tits, at both breeding areas was also quantified. We analysed long-term trends in the timing of egg laying and clutch size. We focused on the effects of year, habitat type, insect availability and weather conditions shortly before egg laying on the patterns of variation in laying date and clutch size. In general, our study supports earlier generalisations on urban and rural tit populations. In particular, our finding that great tits initiated breeding consistently earlier in the urban site than in the forest area supports earlier studies on urbanised birds. The mean la... Resumen. Muchos estudios en diferentes sitios de Europa han mostrado que las poblaciones de páridos que crían en nidales artificiales en áreas urbanas ponen antes y producen menos huevos que las de áreas rurales. Durante 11 años tomamos datos en el centro de Polonia sobre fechas y tamaños de puesta en dos poblaciones de carbonero común Parus major en bosques caducifolios de robles y parques urbanos, separados por unos 10 km. Además, se cuantificó la abundancia de orugas, el alimento óptimo de los carboneros durante la nidificación. Analizamos las tendencias a largo plazo en fechas y tamaños de puesta, centrándonos en los efectos del ano, tipo de hábitat, disponibilidad de insectos y condiciones climáticas justo antes de las fechas de puesta sobre los patrones de variación en fechas y tamaños de puesta. En general, nuestro estudio apoya las generalizaciones previas sobre páridos urbanos y rurales. Específicamente, nuestro resultado mostró que en el área urbana los carboneros comenzaron consistentemente a p...

A major function of birds’ nests is to protect eggs and offspring against temperature fluctuations. Reproductive performance was found to be closely related to nest characteristics in some species. We present results concerning nest attributes and their impact on breeding characteristics in Blue Tits ( Cyanistes caeruleus) and Great Tits ( Parus major) in central Poland over a three year period, 2012-2014, in an urban parkland and a deciduous forest. In Blue Tits, hatching success was positively affected by the nest lining mass. Clutch size was associated with the lining mass and nest mass, and the number of hatchlings was associated with both the nest mass and lining mass. In Great Tits, hatching success was positively affected by the lining mass and fledging success was positively affected by the nest depth and nest mass. Also, clutch size tended to be related to the nest depth and the number of hatchlings was associated with the lining mass. We found that Blue Tit nests were deeper and heavier than Great Tit nests. There were no differences in nest depth and nest mass between two habitats for both tit species. We conclude that there is a relationship between better quality nests and better breeding performance in both Great Tits and Blue Tits.

The impact of climatic changes on life cycles by re-scheduling the timing of reproduction is an important topic in studies of biodiversity. Global warming causes and will probably cause in the future not only raising temperatures but also an increasing frequency of extreme weather events. In 2013, the winter in central and north Europe ended late, with low temperatures and long-retained snow cover—this extreme weather phenomenon acted in opposition to the increasing temperature trend. In 2013, thermal conditions measured by the warmth sum in the period 15 March–15 April, a critical time for early breeding passerines, went far beyond the range of the warmth sums for at least 40 preceding years. Regardless of what was the reason for the extreme early spring 2013 and assuming that there is a potential for more atypical years because of climate change, we should look closely at every extreme phenomenon and its consequences for the phenology of organisms. In this paper, we report that the prolonged occurrence of winter conditions during the time that is crucial for Blue Tit (Cyanistes caeruleus) and Great Tit (Parus major) reproduction caused a substantial delay in the onset of egg laying in comparison with typical springs.