Grzegorz Hebda

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 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.ZusammenfassungNatürliche 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.

40 years of breeding bird community dynamics in a primeval temperate forest (Białowieża National Park, Poland)

Abstract. 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 atricapilla reached the highest ever level, and those of Columba palumbus and Dendrocopos medius equalled the maxima observed during 40 years. The overall breeding densities did not change significantly but they were substantially lower than in the peak year (2001). Crown insectivores, crown nesters and short-distance migrants remained the most numerous foraging, nesting and migratory groups, respectively. The earlier observed density gradient across habitats — highest in the riverine, lowest in the coniferous stands — was retained. Overall composition of the breeding avifauna did not change during 40 years, and no colonization of forest areas by a new species, nor extinction of a formerly widespread species, except A. trivialis, were observed. Some local changes of species richness occurred, however. Large-scale changes in coniferous habitats due to die-back of Picea abies and appearance of canopy gaps were followed by the increase in species richness there, while disappearance of former sharp forest edges reduced the number of species breeding in the “edge” plots. We suggest that the high constancy of species composition of the breeding bird assemblage in BNP results largely from the interplay of two factors: 1) long-term stability of the forest habitats, causing places suitable in one year to remain so over many seasons, and 2) cross-generational reproducibility of the selection criteria used by the birds in their settlement decisions.

Disappearance rates of old nest material from tree cavities: An experimental study

Abstract Numerous forest organisms critically depend on availability of tree cavities. Some birds and rodents fill their cavities with bulky nests, which – if not removed – could accumulate and render cavities unusable, as recorded in nest-box studies. Data from earlier studies indicate that old nests can disappear from tree cavities so fast that practically no remnants are detectable the following spring. Rapid decomposition of nests in situ, augmented by physical removal of nest material by the cavity-users have been proposed as possible causative mechanisms. We tested these hypotheses in cavities used by tits (Parus major L., Poecile palustris L.) in the Białowieża National Park (E Poland). To mimic typical components of their nests – moss and mammalian hair – we inserted into cavities litter-bags filled with either cellulose or fleece of sheep. After 9,5 months of exposure a third of bags were missing from cavities, and 92–100% of cellulose and 84–98% of hair disappeared from the remaining ones. These results confirm that the rapid decomposition of the tit nests in cavities reinforced by material removed by vertebrates would suffice to “clean” the cavities between the consecutive seasons. To conclude, accumulation of litter in natural nests holes does not seem to affect nest hole availability.

Nest-site competition between bumblebees (Bombidae), social wasps (Vespidae) and cavity-nesting birds in Britain and the Western Palearctic

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. 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. 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. 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). 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.

Decomposition rate of old nest material in tree holes

Abstract. We experimentally tested whether old nest material could decompose fast enough to clear tree holes between the consecutive seasons. To mimic the nest material we filled litter-bags with either 1 g of cellulose, or with 0.5 g of dog moulted hair. In August 2009 we placed pairs of these bags in 23 tree holes used by breeding birds in a deciduous forest in SW Poland. For reference, we placed the same sets of bags in the litter, at 23 random sites in the forest. The bags were removed in March 2010. After seven months of exposure almost all cellulose (median 92%) and most of hair (median 57%) disappeared from bags in the holes. These values were as high as (for cellulose) or even higher than (for hair) as in the litter samples. Additionally, some bags disappeared from almost every second hole, which suggests their removal by larger animals. The high decomposition rates alone would suffice to clear holes between consecutive seasons but, in the study area, this process was apparently enhanced by mechanical cleaning.

Morphology, geographical variation and the subspecies of Marsh Tit Poecile palustris in Britain and central Europe

Capsule All British Marsh Tits belong to subspecies Poecile palustris dresseri, being smaller than nominate P. p. palustris of central Europe. Aims Determining the subspecies of Marsh Tit in Britain to test whether ssp. P. p. palustris occurs in northern England and Scotland, by assessing regional variation in size compared with central European birds. Methods 1147 wing length and 250 tail length measurements from 953 Marsh Tits were compared between eight British locations to test for regional variation. Biometrics were compared between birds from Britain and six locations within the continental European range of ssp. palustris. Results There was no regional variation in wing or tail lengths among British Marsh Tits, indicating that all resident birds belong to ssp. dresseri. There was no evidence supporting the existence of ssp. palustris in northern England. British birds were significantly smaller than those from continental Europe, with proportionately shorter tails, consistent across all age and sex classes. Conclusion All British Marsh Tits should be considered as ssp. dresseri, with ssp. palustris being limited to continental Europe. With no evidence of regional variation in size within Britain, reliable sexing methods based on biometrics could be applied in demographic studies throughout the country.

Inter-specific nest re-use by barn swallows Hirundo rustica

ABSTRACT Capsule: Reports of inter-specific nest re-use by Barn Swallows Hirundo rustica in Europe and North America are reviewed. Inter-specific nest re-use was rare but appeared opportunistic, possibly functioning as a time-saving mechanism or as a result of limited nest sites.

Nest Sites of a Strong Excavator, the Great Spotted Woodpecker Dendrocopos 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 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. tremula, and in all habitats Norway Spruce Picea abies and Small-leaved Lime Tilia cordata were clearly avoided. The woodpeckers generally excavated in large trees (median diameter at breast height: 50 cm), high above the ground (median 11 m), mostly in the trunks (83%) of living trees (67%). Overall, 21.7% of entrance holes were facing downwards. This pattern of hole placement is similar to that reported from other mature forests in Europe. We stress that despite very high plasticity in this species, it seems to use a distinct set of criteria for nest site selection that is related to predation risk, microclimate and mechanical damage of the place of excavation.

Decomposition of Nest Material in Tree Holes and Nest-Boxes Occupied by European Starlings Sturnus vulgaris: An Experimental Study

Abstract. Numerous bird species depend on the availability of tree cavities, and most non-excavators fill their cavities with considerable amounts of nest material. If not removed, this material can accumulate and render cavities unusable, as recorded in some nest-box studies. Data from earlier studies of tree cavities, however, showed that nest material can decrease mostly due to in situ decomposition, but the relative difference between nest decomposition in tree holes and nest-boxes is still unknown. We undertook parallel studies of decay in tree holes and nest-boxes used by European Starlings Sturnus vulgaris in oak-hornbeam stands (SW Poland). We inserted into its tree holes and nest-boxes litter-bags filled with cellulose and wool. After 7.5 months of exposure we detected much greater decomposition in tree holes than in nest-boxes. In tree holes a median 75% of cellulose and 26% of wool disappeared, whilst in nest-boxes a median of only 2% of cellulose and 14% of wool. These results are the first to document the relative difference between natural and artificial breeding cavities in the extent of nest decomposition. We also discuss the effect of nest material accumulation in tree holes and nest-boxes on the different nesting conditions available for hole-nesting birds. Taken together with: microclimate, nest safety, competition with social insects and presence of ectoparasites, the physical accumulation of nest material appear to be distinctive feature that differentiates the natural and artificial sites of tree-hole-nesting birds.

Cohabitation of tree holes by ants and breeding birds in a temperate deciduous forest

ABSTRACT A previously unknown association of ants with birds breeding in tree holes is described. Ants Lasius brunneus Latreille (Hymenoptera: Formicidae) were found in c. 15% of nests of Parus major L. and Poecile palustris L. (Paridae) breeding in tree holes in the primeval deciduous forest located in the Białowieża National Park (Poland). The ants preferably used holes located higher above the ground. As such holes are warmer than the unused holes or other nest sites, it is suggested that the ants cohabit holes utilized by the tits to gain thermal benefits.