We documented the composition and structure of the breeding bird assemblage in the primeval temperate forest of the Białowieża National Park (BNP), during 2010–2014, and used 40 years of data to assess patterns of its diversity. We applied an improved version of the mapping technique (a combined mapping method) for forest birds in seven plots located in three old-growth forest types: ash-alder riverine, oak-hornbeam, and mixed coniferous. The composition of the breeding avifauna and species richness remained basically unchanged. Jointly 67 (79% of 40-year total) breeding species were recorded in 2010–2014. Overall 49 (57%) of all species bred in the study plots in more than 35 years, they formed c. 97% of the pairs in the breeding assemblage. The composition of the group of dominants changed slightly; Phylloscopus sibilatrix became much less numerous in comparison to the earlier periods. Anthus trivialis ceased to breed — possibly due to disappearance of its habitat. The numbers of Sylvia atrica...

An overlap in attributes of nest cavities used by Great Tit Parus major across Eurasia suggests similar nest site preferences within the geographical range, although the drivers of these preferences are unclear. To determine whether preferred cavities provide conditions enhancing successful reproduction, we investigated the breeding performance of Great Tits in relation to tree cavity characteristics using data collected during 2008–2011 in primeval conditions (Białowieża National Park, Poland). Here, tree cavities are diverse and superabundant but nesting birds are at risk from a variety of predators. According to expectations, nest losses were high (60 % of Great Tit nests failed), mostly due to predation (69 % of nest failures). The risk of nest failure varied with nest cavity attributes. Compared to successful nests, failures were situated higher above the ground and placed closer to the cavity entrance. Very deep cavities with narrow entrances and strong livings walls provided effective protection against larger predators (e.g., martens, woodpeckers), unable to enter the cavity or pull out the contents. Yet, such holes were no barrier for the smallest predators (e.g., Forest Dormouse Dryomys nitedula), which were able to enter any Great Tit nest cavity and destroyed most of the nests. Avoiding small predators would give a selective advantage to the birds, but this seems hardly possible to achieve. We conclude that tree cavities preferred by the tits show a combination of properties which are a compromise for avoiding predation (the strongest selective pressure) and providing the minimum requirements (sufficient nest illumination, microclimate, protection against nest soaking) for development and growth of young.

Knowledge of the breeding ecology of the Great Tit Parus major is vast, but almost exclusively concerns birds using nest-boxes. Information on birds nesting in natural conditions is scant. Here, we present the results of the first thorough study on natural nest-sites of the Great Tit. The data, including descriptions of nest-cavity location and dimensions, were collected during 39 breeding seasons in the primeval forest of Białowieża National Park (BNP), Poland. With an excess of available tree-cavities providing a diverse choice of nesting options, Great Tits nested mainly in non-excavated, very deep and spacious cavities with elongated, narrow openings, placed at intermediate heights in living tree trunks. Different sets of tree species were used in different habitats. The pattern of nest-site utilisation by Great Tits in BNP overlapped with that recorded in other areas, but showed niche separation from other non-excavating hole-breeders in BNP. This indicates that Great Tits have core nest-site preferences, which have probably evolved in response to selective forces such as, e.g., risk of predation, flooding, sufficient nest illumination and/or efficient air ventilation. Natürliche Nistplätze der Kohlmeise in einem Urwald (Białowieża Nationalpark, Polen) Das Wissen über die Brutökologie der Kohlmeise (Parus major) ist sehr groß, bezieht sich aber fast ausschließlich auf Vögel, die in Nistkästen brüten. Informationen über Vögel, die unter natürlichen Bedingungen brüten, sind rar. Hier stellen wir die Ergebnisse der ersten umfassenden Untersuchung vor, die sich mit natürlichen Nistplätzen der Kohlmeise beschäftigte. Die Daten, darunter Beschreibungen der Lage und Dimension der Nisthöhlen, wurden während 39 Brutzeiten im Urwald des Białowieża Nationalparks (BNP) in Polen gesammelt. Bei einem Überschuss an verfügbaren Baumhöhlen, der eine vielfältige Auswahl von Nistmöglichkeiten zur Verfügung stellte, brüteten die Kohlmeisen hauptsächlich in natürlichen, sehr tiefen und geräumigen Höhlen mit länglichen, schmalen Öffnungen, in mittlerer Höhe von Stämmen lebender Bäume. In unterschiedlichen Habitaten wurden andere Baumarten gewählt. Das Muster der Nistplatzwahl der Kohlmeisen im BNP überlappte mit dem in anderen Gebieten aufgezeichneten, zeigte aber eine Nischentrennung von anderen Höhlenbrütern, die in natürlichen Höhlen brüteten. Das zeigt, dass Kohlmeisen grundlegende Nistplatzpräferenzen haben, die sich wahrscheinlich als Antwort auf einen Selektionsdruck entwickelt haben, wie zum Beispiel Prädationsrisiko, Überschwemmungsgefahr, ausreichende Ausleuchtung der Bruthöhle und/oder Ventilation.

Capsule: There is no evidence of widespread significant nest-site competition in Britain or the Western Palearctic between cavity-nesting birds and bumblebees or social wasps.\ud Aims: To investigate competition between cavity-nesting birds and bumblebees and wasps, particularly the range-expanding Tree Bumblebee, Saxon Wasp and European Hornet in Britain, and review evidence throughout the Western Palearctic.\ud Methods: We compared field data from English and Polish studies of tits and woodpeckers breeding in nest-boxes and/or tree holes to assess nest-site competition with bumblebees and wasps. We reviewed the literature quantifying nest-site competition between birds and these insects in the Western Palearctic.\ud Results: Bumblebees and wasps are capable of usurping small passerines from nests. In England, these insects commandeered a mean annual 4.1% of tit nests initiated in nest-boxes; occurrence of hornets showed a long-term increase, but not other wasps or bumblebees. Across the Western Palearctic, insect occupation of nest-boxes was generally low, and was lower in England than in Poland. No insects were discovered in tree cavities, including those created by woodpeckers (Picidae).\ud Conclusion: Nest-site competition between cavity-nesting birds and bumblebees and wasps appears to be a ‘nest-box phenomenon’, which may occasionally interfere with nest-box studies, but appears negligible in natural nest-sites

Warmer winters may lead to changes in the hibernation behaviour of bats, such as the barbastelle Barbastella barbastellus, which prefers to hibernate at low temperatures. The species is also known for its large annual fluctuations in the number of wintering individuals, so inference about population trends should be based on long-term data. Prior to 2005, analyses indicated stable or even increasing barbastelle population in Poland. We analysed the results of 13 winter bat counts (2005–2017) of the species from 15 of the largest hibernacula, and additional site of 47 small bunkers, in Poland. The total number of wintering individuals remained stable during the study period, because the barbastelle is not a long-distance migrant, this likely reflects the national population trend. On the basis of mean winter air temperatures we divided the country into four thermal regions. Analyses of barbastelle abundance in hibernacula in the four regions revealed a 4.8% annual mean increase in numbers in the coldest region, where mean winter temperatures were below -2°C, annual mean declines of 3.3% and 3.1% in two warmer regions of western Poland, but no trend in the region of intermediate mean winter temperatures of between -1°C and -2°C. Overall, there was a significant, but weak, negative correlation between the abundance of hibernating individuals and the mean winter temperature. On the other hand, the number of individuals hibernating in small bunkers increased, even though the site was located in one of the warm regions. The results indicate a warming climate will likely reduce the use of large, well-insulated winter roosts by species that prefer colder conditions–and that this is already happening. For forest-dwelling bats, such as the barbastelle, for which monitoring schemes are primarily based on winter surveys of large hibernacula, estimations of population trends may consequently become less reliable.

In managed forests, birds that create their own breeding holes in trees have limited access to substrates in which they can excavate. Therefore, nest site use in these forests possibly reflects availability of substrates more than species preferences. We analysed data on nest sites of Great Spotted Woodpeckers Dendrocopos major collected during 1987–2013 in the strictly protected part of Białowieża National Park in East Poland. The woodpeckers excavated breeding holes in 11 tree species, but species used in individual habitats varied greatly: Alder Alnus glutinosa was almost the only species used in the riverine forest; Aspen Populus tremula, Hornbeam Carpinus betulus and Pedunculate Oak Quercus robur were used most often in oak-lime-hornbeam forest, whereas Scots Pine Pinus sylvestris and P. tremula were used most in coniferous habitat. In oak-lime-hornbeam habitat, the birds strongly preferred to excavate in P. tremula and Q. robur, in the coniferous habitat the birds preferred P. sylvestris and P. trem...