Variation in clutch size in relation to nest size in birds

Peer reviewe

Foraging behaviour of the Great Spotted Woodpecker (Dendrocopos major) in the Białowieża National Park: Comparison of breeding and non-breeding seasons

Although the Great Spotted Woodpecker (Dendrocopos major) is the most common of the European woodpecker species, there are no studies detailing its foraging behaviour in the breeding and non-breeding seasons. Our research, conducted in the primeval oak-lime-hornbeam forest of the Białowieża National Park in 1999–2011, compared foraging sites and foraging techniques used by this species in these two seasons. Great Spotted Woodpecker predominantly foraged on standing trees, while lying trees and the ground were occasionally used as foraging sites, but almost exclusively in the breeding season. European hornbeam (Carpinus betulus) and small-leaved lime (Tilia cordata) were the most frequently used for foraging in the breeding season, whereas Norway spruce (Picea abies) and pedunculate oak (Quercus robur) were used in the non-breeding season. Great Spotted Woodpecker foraged more frequently on dead and large trees in the non-breeding season. In the breeding season, Great Spotted Woodpecker collected food mainly from living substrates, predominantly sites on large diameter trunks and at low height, while in the non-breeding season it collected food from thin, dead and upper branches. Searching for food and gleaning it from the tree surface was the most common foraging technique used in the breeding season, whereas seed extraction from cones dominated in the non-breeding season. The percentage of foraging time spent on this type of food was positively correlated with the index of Norway spruce seed production. Our study showed that the foraging behaviour of the Great Spotted Woodpecker in the two seasons differs significantly due to changes in food resources

How woodpeckers can save the Białowieża Forest?

Economic benefits of woodpecker watching at the Białowieża Forest Białowieża Forest (BF) is very famous for bison, beautiful old-growth stands and rich avifauna (e.g., woodpecker, owls, birds of prey, flycatchers). That's why this place attracts a lot of tourists who are interested in nature. Among people visiting the BF birdwatchers are the most important group consisting about 1/3 of tourists. The goal was to estimate the value of the White-backed Woodpecker Dendrocopos leucotos (WBW) and the Three-toed Woodpecker Picoides tridactylus (TTW) at BF, i.e., calculating how much money the visiting tourists leave to see these birds. The results were compared to the benefits derived from wood production. We conducted surveys among birdwatchers visiting BF in 2016. We asked them about bird species they wanted to see the most and about their costs of staying in Białowieża. Data on timber production we obtained from State Forest. Birdwatchers the most frequently indicated WBW and TTW. People who wanted to see at least one of these two species spent in Białowieża a total of 5.5 million euro, which is 34% of the total amount spent annually by all tourists. The woodpeckers are considered as indicator species associated with other natural features of the forest. As many as nine woodpecker species breed in BF, but their densities are rather low and the number of some rare species decrease. The most sensitive to habitat changes due to forest management (logging, removal of dead trees) are WBW and TTW. In 2017, as much as 170,000 m3 of wood was removed from the BF. In many cases, logging was conducted along forest roads and tourist trails (dozens of kilometers). This worsened: 1) of woodpecker habitats, and 2) possibility to explore the forest by birdwatchers. It is worth to stress that, revenues from birdwatchers interested in WBW and TTW were higher than revenues from logging. Moreover, revenues from that kind of tourism goes to hundreds of local people (guides, shops, restaurants and rooms owners etc.), while revenues from timber production goes to big state company employing relatively small group of people. Significant money from birdwatchers could convince lawmakers that constant protection of all old stands in the entire BF can be more beneficial for both, the local community and nature. peerReviewe

Foraging Site Selection of the Middle Spotted Woodpecker (Leiopicus medius L.) in Primeval Oak-Lime-Hornbeam Forest of the Białowieża National Park: Comparison of Breeding and Non-Breeding Seasons

The distribution of the Middle Spotted Woodpecker (Leiopicus medius) is restricted to mature deciduous forests with large trees, mainly oaks (Quercus spp.). Intensive forest management resulted in the loss of many suitable habitats, thus resulting in a decline in the population of this species. This study aimed to identify the parameters of foraging sites in the breeding season (April to June) and in the non-breeding season (other months). The research was conducted in the primeval oak-lime-hornbeam forest of the Białowieża National Park, where foraging woodpeckers were observed and detailed parameters of foraging sites were recorded. During the breeding season woodpeckers foraged primarily on European hornbeams (Carpinus betulus L.), but in non-breeding season the use of this tree species decreased by a factor of two, whereas the use of Norway spruces (Picea abies L.) increased more than twice. The most preferred tree species as a foraging site in both seasons was pedunculate oak (Quercus robur L.). In the non-breeding season, woodpeckers foraged at sites located higher, and the foraging session was longer compared with the breeding season. In both seasons, woodpeckers preferred dead and large trees and prey gleaning from the tree surface was their dominant foraging technique. Our results confirmed the key role of oaks and large trees, but also revealed the importance of European hornbeams and Norway spruces as foraging sites for the Middle Spotted Woodpecker

Spatial niche segregation between bird species in the Białowieża primeval forest (NE Poland)

Drivers of bird niche separation in temperate primeval forests have not yet been determined, due to the low number of intact forest sites. Here, we analyzed the general patterns of niche usage on trees by birds’ assemblages. We tested how tree species affect the sharing of space in an assemblage of birds and their level of specialization. We conducted our study in the Białowieża primeval forest (NE Poland). During two breeding seasons, we observed bird positions on trees, divided into three vertical and six horizontal zones in 768 observation points. Based on the interaction networks framework we calculated the Kullback-Leibler distance d′ as a metric of species specialization and the resource range RR index, which estimates the species’ specificity based on the fraction of space utilized with a non-zero performance. The d′ index was the highest in the lower understory for all parts of the tree on the basis of the position from the trunk. The RR index was the highest in the lower understory for all parts based on the position from the trunk. Regarding the tree species, the lowest d′ index was observed in all tree species together, and hornbeam, whereas the highest in oak. At the tree species level, the RR index was the lowest for hornbeam. We show tree species importance in forest space sharing in the case of bird assemblages. Hornbeam, alder, and spruce are universal species that were used by birds almost entirely. In contrast, oak, lime, and maple were only partially used. Tree species with less complex structures could shape bird assemblages, as they could offer birds much fewer niches to realize. Therefore, we showed that high specialization and niche separation are drivers of high bird diversity. Consequently maintaining a diverse stand structure is crucial for biodiversity conservation

Early post-fire bird community in European boreal forest: Comparing salvage-logged with non-intervention areas

Salvage logging after disturbances in forests substantially modifies vegetation structure and dead wood availability, but empirical evidence on its impact on biodiversity, especially in European boreal forest, is sparse. In this study we investigated the short-term effect of post-fire salvage logging on species richness and abundance of birds in recently burned mixed coniferous forest. Using point counts we estimated local species composition at 49 salvaged sites and 55 non-intervention sites (burnt forest left for natural regeneration) that were not logged after a fire in south-central Sweden. Local species richness, abundance and Simpson's species diversity index were significantly higher at non-intervention sites compared to salvaged sites. Forest birds that rely on structurally complex forest stands, such as tits (Parus major, Lophophanes cristatus, Poecile montanus), robin (Erithacus rubecula), mistle trush (Turdus viscivorus) and tree-toed woodpecker (Picoides tridactylus) were mainly associated with non-intervention sites, while species that are typically linked to farm- or shrublands, such as whinchat (Saxicola rubetra), white wagtail (Motacilla alba), red-backed shrike (Lanius collurio), and meadow pipit (Anthus pratensis) were more common at salvaged sites. These results are consistent with the idea that post-fire salvage logging has an immediate impact on the bird species composition and abundance in boreal forest. We conclude that although post-fire salvage logging may be beneficial for birds occurring in open landscapes, it has negative effects for forest bird species richness and abundance, at least over the short term. To protect typical forest communities with many forest specialists of high conservation concern, we recommend reducing the extent of post-disturbance salvaging in forests of high conservation value and updating the existing management policy to restore the amount of woody debris and facilitate long-term structural complexity and biodiversity in densely stocked conifer stands. Keywords: Natural disturbance, Forest management, Salvage logging, Forest fire, Boreal forest, Bird communitie

Characteristic of tree cavities in sal <i>Shorea robusta</i> forest, Nepal

<p>Tree cavities are one of the key structures that influence abundance and diversity of cavity-dependent organisms in forests. The natural processes that lead to cavity formation and regulate the abundance of cavities are poorly understood, especially in subtropical regions of Asia. Surveys of tree cavities suitable for breeding birds were conducted in southern Nepal in sal <i>Shorea robusta</i> dominated forest. A cavity was defined as a hole in a tree trunk or a limb with a minimum entrance diameter of 2 cm × 2 cm, interior space, depth at least 2 cm and a solid bottom with a minimum diameter of 5 cm. Within 50 sample plots, we found 104 tree cavities. The mean height of cavity entrances (6.8 m above the ground) varied across tree species from 3.4 m in <i>Dillenia pentagyna</i> to 10.3 m in <i>S</i>. <i>robusta</i>, and was positively correlated with DBH of tree. The entrance exposures were most often to the south (38.2%), and located mainly in trunks (74.0%). Cavity entrances were very different in size, with mean smallest diameter 7.7 cm, the average depth of the cavity was 25.7 cm. Mode of cavity production (excavated or non-excavated) was best predicted by a model including diameter of cavity tree (DBH), cavity height and their interaction. Single check of cavities showed signs of use by birds in 21% of them. Excavated cavities accounted for 27.9% of all cavities, indicating that role of woodpeckers as cavity providers might be of importance for secondary users in sal forest.</p