Bialowieza National Park Research Articles

Foraging Behaviour of the Great Spotted Woodpecker Dendrocopos major in Relation to Sex in Primeval Stands of the Białowieża National Park

The Great Spotted Woodpecker Dendrocopos major in spite of its broad food niche may prefer some trees or places on them during foraging. Different preferences for foraging sites can also be found in males and females, which may minimize competition for food between them. The main goal of our study was to define sex-specific use of foraging sites of the Great Spotted Woodpecker, in the primeval oak-hornbeam-lime forest of the Bialowieza National Park, E Poland. This forest has never been logged and is distinguished by the structure of great vertical and horizontal diversity, high amount of dead wood and trees which reach large dimensions. Therefore, there are a large number of potential foraging sites, and some trees, due to their species or condition, may be particularly preferred in this respect. Our study revealed that the foraging sessions of woodpeckers were longer on the dead parts of trees than on alive ones which were especially noticeable in the case of females. The longest foraging sessions were found on dead parts of Norway Spruce Picea abies for both sexes. The males foraged the longest at high altitudes (> 20 m above the ground) on thin parts of trees (diameter 5–10 cm) whereas females on sites above 15 m and on thicker parts of tree (diameter 10–20 cm). Moreover, the duration of foraging session of females increased with increasing of trunk diameter at breast height, which was not revealed in males.

Multi-scale settlement patterns of a migratory songbird in a European primaeval forest

The drivers of animal settlement are core topics in ecology. Studies from primaeval habitats provide valuable but rare insights into natural settlement behaviour, where species are unconstrained by habitat fragmentation and modification. We examined whether territorial male songbirds (wood warblers Phylloscopus sibilatrix) exhibited clustered distributions when settling in extensive primaeval forest. We tested whether settlement patterns were consistent between years, the influence of habitat preference and the spatial extent of these processes. Remote sensing (airborne LiDAR and satellite multi-spectral) and field survey data were combined to investigate settlement at the landscape (tens of km2), plot (46–200 ha) and microhabitat (20 m diameter) scales, by sampling across 5.9 × 4.5 km of the Bialowieza National Park (Poland) during 2018–2019. We assessed bird distribution patterns using nearest neighbour analyses, and habitat preference with generalized linear mixed models. Variation in bird density between plots and years was suggestive of large-scale clustering at the landscape scale. At the local plot scale, any clustering was masked by territoriality, with birds appearing dispersed or randomly distributed. At the microhabitat scale within territories, birds preferred a tall, closed canopy forest structure and avoided a dense herb layer of wild garlic patches. Settlement appeared unconstrained by the availability of preferred habitat at the plot scale, which remained unsaturated. Wood warbler settlement apparently involved hierarchical decisions at multiple spatial scales, compatible with potential social attraction, territoriality, habitat preference or predator avoidance. Selecting an appropriate scale of analysis is an important consideration when assessing the clustering of territorial species. Many songbirds settle in clusters of breeding territories, possibly reflecting patchy habitat quality and/or social attraction. Studies of territory clustering generally come from fragmented, modified habitats, such as secondary forest, which might bias or limit bird distribution. We studied settlement patterns of male wood warblers in an extensive, primaeval forest, where they could exhibit natural behaviour. Spatial analyses of satellite, airborne and field survey data revealed a series of settlement decisions at multiple spatial scales. We found evidence supporting large-scale clustering across the forest, but at the local scale any such clusters were masked by the spacing of birds within territories. A tall forest structure was preferred within the territories, but at larger scales, some birds seemed to compromise habitat quality to settle within a cluster. The results highlight that settlement decisions of animals must be considered at appropriate spatial scales.

A refined genome-wide association study of posthitis in lowland Białowieza population of the European bison (Bison bonasus)

Necrotic inflammation of the prepuce (NIP, posthitis) is probably the most serious threat to the males of European bison (Bison bonasus) population living in the Bialowieza National Park. Approximately 6% of the males have been affected every year. The aim of this study was to explore genetic regions potentially affecting this disease. The population was divided into two groups: healthy (25) and affected by posthitis (112). All individuals were genotyped with the Illumina BovineHD BeadChip. Tests performed on a single-locus mixed model (EMMAX) resulted in one SNP on the 25th chromosome (rs134172402) showing statistically important association with the posthitis incidence. The closest candidate gene located near this SNP was the periplakin (PPL) coding protein associated with skin development and some autoimmunity skin diseases such as pemphigus foliaceus or atopic dermatitis. Therefore, we conclude that PPL might be the candidate gene for posthitis, but further studies are necessary to confirm its expression and role in affected tissues.

Food of Nuthatch Sitta europaea Young in a Primeval Forest: Effects of Varying Food Supply and Age of Nestlings

Information on nestling diet composition is crucial for understanding the variation in birds breeding seasons at both the ultimate and proximate levels. We studied Nuthatch nestling food composition along with availability of its presumed main food resource — folivorous caterpillars — in a primeval forest, free from direct human impact (Bialowieza National Park, Poland), in 1998–2004. Food brought to young during 4281 feeding visits (235 broods) was recorded. Nestlings were fed mostly caterpillars (53% of visits), but winged insects (14%), beetles (11%) and spiders (10%) were also regularly provided. The proportion of caterpillars increased with increasing caterpillar availability (measured by frassfall), with a maximum around the seasonal peaks and a later decline. The proportion of caterpillars in the diet was lower on days when frassfall was low (< 0.1 g/0.25 m2/day), irrespective of the temporal distance from the frass peak, while the proportion of winged insects increased on such days. Above the 0.1 g frassfall threshold, the proportion of caterpillars regularly exceeded 50%, reaching 90% on individual days. As in the majority of years the ‘caterpillars’ remained above the 0.1 g level over long periods, this could account for a comparably small interyear variation in the proportion of caterpillars in the diet, despite nearly tenfold differences in caterpillar abundance across years. ‘Caterpillars’ were brought significantly less often to the smallest, 5-day old, nestlings (52%), than to older ones (64%, 71% and 72% for 10-, 15- and 20-days old young, respectively). Spiders were most often provided to the smallest nestlings.

Occupation of wood warbler Phylloscopus sibilatrix nests by Myrmica and Lasius ants

Bird nests can provide habitats for various invertebrates, including ectoparasites, scavengers, and predators. Records of ants associating with active bird nests mostly involve the insects searching for food, with some exceptional records of ants raising their broods (eggs, larvae or pupae) within songbird nests in nest-boxes or tree cavities. We present data for a previously undocumented, but apparently regular, occurrence of ants and their broods within the active nests of a songbird, the wood warbler Phylloscopus sibilatrix (Bechstein, 1793), which builds domed nests on the ground in European forests. Systematic recording found ants, mostly Myrmica ruginodis Nylander, 1846, in 43% of 80 wood warbler nests in the primary forest of Bialowieza National Park (Poland) during the springs of 2016–2017, including ant broods in 30%. Ad hoc records from this site in 2004–2015 found ants in a further 29% of 163 nests, including broods in 20%, indicating a regular association. However, examination of 37 nests from secondary forest in Switzerland and Great Britain founds ants in only 14%, and broods in just 5%. We discuss the potential drivers and mechanisms of the observed association between breeding wood warblers and ants, including the apparent difference in frequency between the primary and secondary forests.

Song ThrushTurdus philomelosand HawfinchCoccothraustes coccothraustesExhibit Non-Random Nest Orientation in Dense Temperate Forest

Patterns of bird nest orientation in dense forest interiors are relatively unknown. Using data collected in primeval temperate forests at the Bialowieza National Park in Poland, we found that two arboreal nesting species, the Song Thrush Turdus philomelos and the Hawfinch Coccothraustes coccothraustes, located significantly more of their nests in the southern half of tree crowns than in the northern half. Nest orientation also depended on nest height: the higher Song Thrush and Hawfinch nests were in the crowns of trees, the stronger preference both species had for locating their nests toward the south. For the Song Thrush, tree species interacted with the date of clutch initiation to influence patterns of nest orientation: Song Thrushes located more of their nests on the ‘south-facing’ sides of live Norway Spruces Picea abies as the nesting season progressed. Spring temperature during the nest construction period affected Hawfinch nest orientation, with significantly more ‘south-facing’ nests during colder springs. The directional orientation patterns we observed may be viewed as a response of nesting birds to weather conditions during nest site selection and nest construction periods, when exposure to solar radiation could help regulate nest temperatures during cold mornings or days.

Effects of Wild Boar (Sus scrofaL.) Rooting on Seedling Emergence in Białowieża Forest

The wild boar is an omnivorous animal, and by foraging (rooting) disturbs the top soil layer. In some regions of Poland and Europe seasonal fluctuations in rooting have been observed. Wild boars not only eat plants, but also strongly modify their habitat. In Bialowieza National Park wild boar most frequently visit oak-hornbeam forests on fertile soil. On sites where the forest floor is covered with dense vegetation the germination of seeds is difficult, and wild boar rooting can promote the removal of diaspores from deeper layers of the soil seed bank. Within a 3-year observation on 30 subplots about 10,000 seedlings emerged representing 38 species. Our study revealed that rooted patches are characterised by a very rich and diverse flora of seedlings representing mostly forest species, but their density is low. The dominant species germinating in the disturbed ground vegetation is Urtica dioica, a species forming the persistent soil seed bank. There is a possibility that seedlings of herbaceous plants emerging on permanently rooted patches are of exogenous origin, since the seeds germinating there were in many cases damaged by repeatedly rooting animals and had no chance for further growth and reaching the generative phase. However, the soil seed bank in the rooted area has to be analysed to confirm this theory, that they have exogenous or endogenous origin. Seedling density in a repeatedly rooted oak-hornbeam forest is determined by factors other than those related to rooting. In this context the present study did not demonstrate a negative impact of rooting intensity on seedling emergence.

Failed predator attacks: A direct test of security of tree cavities used by nesting Marsh Tits (Poecile palustris)

ABSTRACT Birds that nest in tree cavities, despite being relatively safe, are still threatened by predators, which not only can destroy broods but also can kill the parents. Therefore, using safe cavities is crucial for the survival of parents and nestlings. Safe cavities should simultaneously have the smallest entrance (yet large enough to admit the cavity occupant), walls made of hard wood, and depth sufficient for the nest to be placed beyond the reach of predators. I studied nests of Marsh Tits (Poecile palustris) that were attacked by predators and compared cavity features of nests that survived the attack with those that did not. Observations were gathered in pristine conditions (Bialowieza National Park, Poland) over 30 yr. There was no direct human interference, and cavities were superabundant. I observed 169 attacks on Marsh Tit broods by a diverse set of predators. Nests survived ∼30% of these attacks. Only 10% survived when a predator entered the cavity, but 29% survived if the predator attemp...

A Non-Soil Seed Bank Dependent on the Size of Clonal Plants: The Case ofCarex cespitosa, a Guerrilla Species in an Unmown Meadow

ABSTRACT Long-lived clonal plants provide an optimal place for the natural storage of seeds as a ‘non-soil seed bank’. We tested the hypothesis that the size and species diversity of a non-soil seed bank deposited within the clonal plant Carex cespitosa depends mainly on the plant's size. To verify this hypothesis, an experiment was conducted on an unmown meadow in the Bialowieza National Park. The emerging seedlings of different species originating from C. cespitosa tussocks of different size (large and small) were observed under greenhouse conditions for four years. The size of a non-soil seed bank was evaluated based on the number of seedlings. Significant differences in the seedling number were found between large and small sedge tussocks (Mann-Whitney test Z = 3.96, P < 0.001). However, the number of recorded species was independent of tussock size. Both types of tussocks were dominated by meadow, forest and swamp species (in decreasing order). Some of these species are no longer present in the studi...

Diet of Marsh TitPoecile palustrisNestlings in a Primeval Forest in Relation to Food Supply and Age of Young

Composition of Marsh Tit Poecile palustris nestling food was studied in the Bialowieza National Park (E Poland). The birds relied exclusively on natural food sources. Repeated visual observations of food brought to young in over 500 broods, during 14 seasons (1993–2007), showed that Marsh Tit used a highly specialised diet in rearing young. Soft-bodied, folivorous caterpillars typically composed > 80% of the nestling diet both in riverine and oak-hornbeam habitat. Spiders formed the second most important prey type (c. 12%). Diet composition fluctuated across years but the proportion of caterpillars in the diet remained high (70–90%) despite more than hundredfold variation in the caterpillars' supply across years. Within years, diet composition changed with nestling age and the broods' synchronisation with the seasonal peak of caterpillars availability. Young that were fed within 15 days before and 10 days after the peak received a high (> 80%) proportion of caterpillars, independent of their age. The share of caterpillars in the diet dropped only outside of that period. In most seasons, Marsh Tit young appeared in nests more than two weeks before the caterpillar peak; consequently, the share of caterpillars fed to small young in the earliest broods was lowest (c. 62% on average). Marsh Tits strove to collect caterpillars even when they were scarce, rather than switch to alternative food types. Spiders were brought in highest numbers (up to 20%) to the youngest (1–7 days old) nestlings. This suggests that spiders contained specific nutritional ingredients required by the small young.

New insight on the role of melatonin receptors in reproductive processes of seasonal breeders on the example of mature male European bison (Bison bonasus, Linnaeus 1758)

Melatonin receptors (MT1 and MT2) were shown to regulate proper functioning of reproductive system, especially in seasonally breeding animals. European bison is a unique endangered seasonal breeder and knowledge of the molecular mechanisms of its reproduction is crucial for the survival of the species. The aim of this study was to assess gene expression, protein synthesis and immunohistochemical localization of MT1 and MT2 receptors in testicular and spermatic cord vessels tissues collected in pre-rut (June) and post-rut (December) seasons from adult male European bisons in Bialowieza National Park. We confirmed the highest expression of MT1 and MT2 mRNA and protein levels in testis in December, while in spermatic cord gene expression was also highest in December, but protein amounts were comparable in both analyzed periods. Furthermore, immunohistochemical staining revealed the same amount of both receptors in arteries and veins of spermatic cord in both periods and increased amounts in December in Leydig, Sertoli and germ cells. The high level of testicular melatonin in December confirms the inhibition of spermatogenesis and increased anti-oxidant and anti-inflammatory protection. In spermatic cord vessels, it may prevent from age-related changes due to the overexploitation and ensure a constant temperature regardless of changing environmental conditions. This knowledge can contribute to finding a solution of problems associated with male infertility in general and also further explore the mechanisms regulating the proper functions of the male reproductive system.

Nest Sites of a Strong Excavator, the Great Spotted WoodpeckerDendrocopos major, in a Primeval Forest

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 Bialowieza 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...

Spider Assemblages of Hummocks and Hollows in a Primeval Alder Carr in the Białowieża National Park — Effect of Vegetation Structure and Soil Humidity

We studied the species richness, diversity, abundance and guild composition of spider assemblages on the hummocks and in the hollows of the alder carr in the Bialowieza National Park. We also assessed the effect of vegetation structure and soil humidity on spiders settled in these two microhabitats. The spiders were collected from 10 May until 27 October 2001 by pitfall trapping. The main factor which differed between the hummocks and the hollows was soil humidity. In the case of vegetation cover we found some differences between the microhabitats but it was particularly evident in the case of litter, which was higher on the hummocks. Spider species diversity was significantly higher on the hummocks than in the hollows, but the number of individuals captured in both microhabitats was similar. The collected spiders belonged to six guilds and the proportion of spider individuals in particular guilds was significantly different between the hummocks and the hollows. The most abundant guild in both microhabitats was ‘ground hunters’ and the most numerous species was Piratula hygrophila. Our analyses showed that soil humidity positively affected the number of spider species and the number of individuals. Sampling date strongly influenced the number of collected species and spider individuals. Vegetation and litter cover did not have a significant impact on the spider assemblages. Our findings suggest that research conducted only on hummocks in the alder carr does not reveal the real structure of spider assemblages.

Customizing elements of the International Forest Regime Complex in Poland? Non-implementation of a National Forest Programme and redefined transposition of NATURA 2000 in Bialowieza Forest

The International Forest Regime Complex consists of a number of institutional elements aiming to regulate forests. Among them the main line of conflict runs between production-oriented and conservation-oriented elements. Voluntary National Forest Programmes as well as biodiversity conservation policies, such as the Convention on Biodiversity and the EU Natura 2000 policy, reflect the main institutional elements of the forest regime complex. The implementation of such individual regime elements as well as the resulting domestic political customizations and consequences in countries, however, so far received little scrutiny. Before this background, this article aims to analyses the political influence of implementing important production- as well as conservation-oriented elements of the International Forest Regime Complex in Poland alongside with important customizations in both processes. Theoretically, we draw on the framework of four pathways of international influences and combine it with bureaucratic politics theory. Empirically, the current study focuses on qualitative in-depths insights into the so far failed implementation of a National Forest Programme in Poland, as well as the implementation and transposition of the EU NATURA 2000 policy, using Bialowieza Forest as an exemplary case. Our results indicate that the Polish Ministry of Environment has driven both processes. Both regime elements were clearly customized by bureaucratic action during the implementation process. While Nature 2000 triggered international support for protection-oriented interests, the dominant production-oriented bureaucracy overweighed it. The forestry bureaucracy offered to accept additional restrictions of forestry for nature protection, but only because they were linked to a gain in territorial authority over Bialowieza National Park and reduced political expectations about Natura 2000 sites all over the country. This re-definition of a formerly conservation-oriented element into a useful tool for production interests can be seen as an intentional, strategic customization of a regime element. In contrast, the process of creating the National Forest Programme so far failed once and since then is under conflictive negotiation. It was drafted as a detailed, nation-wide management plan, rather than a vague and general symbolic policy document as in most other countries. This exceptional customization of the NFP element in the tradition of management planning eventually threatened the dominant forestry interests and, hence, is seen a case of policy non-implementation.

Nest Sites of Middle Spotted WoodpeckersLeiopicus mediusin a Primeval Forest

Forest management usually reduces the diversity and amount of substrates in which woodpeckers can excavate holes. In such conditions the recorded patterns of nest site selection could reflect a more reduced array of substrates than the species' nest site preferences. We analysed new data on nest sites of Middle Spotted Woodpeckers Leiopicus medius collected during 27 breeding seasons (1987–2013) in the strictly protected fragments of the Bialowieza National Park in Poland. The birds could use diverse excavation substrates, of various statures, that varied in condition from living and healthy to dead and completely rotten. Middle Spotted Woodpeckers used a wide array of tree species, with little overlap in the species used in the riverine habitat (mostly Alnus glutinosa, and Fraxinus excelsior) and oak—hornbeam habitats (Carpinus betulus and Quercus robur). The birds preferred to excavate in Q. robur but avoided Tilia cordata and Picea abies. They placed holes in large trees (median girth at breast height:...

Breeding success of the Great Tit Parus major in relation to attributes of natural nest cavities in a primeval forest

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 (Bialowieza 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.

Morphometry and topography of the coronary ostia in the European bison.

Coronary vessels have been widely studied in many species of domestic and wild mammals. However, there are no available literature reports describing the morphology and morphometry of the coronary ostia of the European bison (Bison bonasus). The aim of this study was to measure the area of the coronary ostia and assess their localisation in the coronary sinuses of the aortic root in the European bison. The study material comprised 27 hearts from European bison of both sexes (16 males and 11 females), from 3 months to 26 years old, inhabiting the Bialowieza Forest (Bialowieza National Park, Poland). The animals were divided into two age groups: ≤ 5 years (group I) and > 5 years (group II). In all the studied European bison, the aortic valve consisted of three semilunar leaflets, left, right and septal. The ostia of both coronary arteries were located beneath the sinotubular junction. The dimensions of the left coronary ostium were larger than those of the right coronary ostium. They were longer by on average 4.5 mm (95% confidence interval [CI] 3.5-5.6 mm), they were wider by on average 1.6 mm (95% CI 1.0-2.2 mm) and they had a larger area by on average 31.6 mm2 (95% CI 22.7-40.5 mm2). This was evident both in young and in adult bison. After adjusting for age, there were no differences in the ostia dimensions between males and females. There were no differences in the structure of the left and right coronary arteries in nine animals. In the remaining 18 animals, there were variations in the morphology of the coronary ostia or additional ostia. Because of the anatomical similarity between the European bison and other ruminants, the results of this study can be applied to the other species including endangered ones.

Effects of forest management on bird assemblages in the Bialowieza Forest, Poland

Abstract: We examined the effects of different intensities of forest management on bird communities in the Bialowieza Forest, eastern Poland. Stands that had been managed for more than 100 years (cutting, planting, removal of dead wood) and stands that were partially protected in nature reserves (sporadic sanitary cutting, removal of dead wood until 2008) were compared with unmanaged stands in the Bialowieza National Park by surveying the bird community during three breeding seasons (2010-2012). Surveys were conducted within three forest habitats: spruce-pine (Pino-Quercetum), lime-hornbeam (Tilio-Carpinetum) and ash-alder (Fraxino-Alnetum). Results showed that habitat structure significantly affected the avian community. The basal area of live trees had a positive effect on abundance of birds, while the density of live trees had negative significant effect on bird abundance and species diversity. We also found significantly lower abundance of insectivorous birds and cavity-nesters in managed compared to unmanaged stands. Birds’ assembly in the spruce-pine and ash-alder stands were most sensitive to management. These results show both that management can be used to sustain bird communities, including species of conservation concern, and that inappropriate management may harm them.

Natural nest-sites of Great Tits (Parus major) in a primeval temperate forest (Białowieża National Park, Poland)

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 Bialowieza 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.

Dispersal in an extensive continuous forest habitat: Marsh Tit Poecile palustris in the Białowieża National Park

Dispersal is one of the least understood features in the life-history of organisms. Theoretical work concentrates on explaining dispersal of organisms in patchy and heterogeneous landscapes, but there are few predictions of dispersal patterns in stable, spatially extensive and largely homogenous landscapes, such as large forests. It is expected that we should observe short-distance dispersal in such places, that, to avoid competition with parents and siblings and incestuous mating, offspring should leave natal patches (natal dispersal), disperse independently in different directions, and move over distances that efficiently minimise the probability of meeting a sibling. Breeding dispersal should be very limited, site tenacity should prevail. To explore these ideas, I use observations of Marsh Tits Poecile palustris (a small passerine specialist of mature forests) made in the strictly protected part of the Bialowieza National Park (Poland) over 21 years. The birds largely followed expectations: all fledglings left their natal territories and dispersed in different directions, and males moved shorter distances than females (median = 570 vs. 1,720 m). Apart from this difference, no influence of population density, fledgling time or family size was observed. No parent–offspring pairing occurred, with just one case of sibling–sibling pairing. After first breeding, individuals remained site-tenacious, as breeding dispersal distances were very short (median ca. 100 m). Such behaviour renders Marsh Tit poorly adapted to cross barriers and undertake long-distance movements, and this is actually observed in fragmented landscapes. Understanding dispersal patterns of organisms from extensive environments would be thus of value for basic and conservation science alike.