Three-toed Woodpecker Picoides Tridactylus Research Articles

Densities of Eurasian Three-toed Woodpecker Picoides tridactylus and sap trees correlate across a latitudinal gradient in Sweden

Densities of Eurasian Three-toed Woodpecker Picoides tridactylus and sap trees correlate across a latitudinal gradient in Sweden

Foraging Behaviour of the Eurasian Three-Toed Woodpecker Picoides tridactylus in Its Peak Abundance After Wildfire

In the boreal biome, forest fires are the most important natural disturbance influencing tree substrate availability and quality for a range of specialized species. This includes the Eurasian Three-toed Woodpecker Picoides tridactylus, which is known to promptly utilize burned forest habitats. However, there are no studies addressing the foraging behaviour of this woodpecker in forests affected by wildfire. Such knowledge could assist the development of efficient post-fire management strategies which are in line with biodiversity conservation objectives. This study describes the foraging behaviour of the Eurasian Three-toed Woodpecker during the breeding season in a forest area of 13,100 ha in southcentral Sweden affected by a major wildfire in 2014. During the second breeding season after fire, we used instantaneous sampling where we observed the foraging behaviour of 28 individuals during a total of 1681 observation minutes. Our results suggest that Norway Spruce Picea abies and larger diameter trees (DBH > 25 cm) are important foraging substrates. However, data on time spent foraging on the different substrates suggest that Scots Pines Pinus sylvestris also are important. In particular, we identified the importance of the root collars, where excavation into sapwood was the main foraging method. Our study was performed during a clearly visible peak of Eurasian Three-toed Woodpecker abundance and this may suggest that the level of food resources available was very high which led to observed foraging patterns not necessarily observed in other types of habitats.

Densities of the Eurasian Threetoed Woodpecker Picoides tridactylus calculated from sap row surveys are on par with estimates from fixed route bird censusing

Species-specific tracks animals can be an effective way of mapping species that are hard to find even if they are present. We used observations of sap rows on trees to calculate densities of Eurasian Three-toed Woodpeckers Picoides tridactylus. We surveyed 14 fixed routes in northern Sweden below the montane forest for sap rows during the autumn of 2020. We used our observations of fresh sap rows together with average home range and proportion of active territories per year derived from the literature, to calculate large-scale woodpecker population density. The density based on sap rows was 0.19 pairs per km2. Densities from fixed route bird observations for different parts of Västerbotten County below the montane forests were 0.13–0.14 pairs per km2, in relative agreement with the estimates from sap rows. We also calculated the population density from fixed route observations in the montane forests, and these were almost three times higher. Our density calculations correspond to 7,900 pairs in Västerbotten County. These results indicate that systematic counts of sap rows can quickly provide credible population density estimates of Eurasian Three-toed Woodpeckers.

Keystone role of Eurasian beaver Castor fiber in creating the suitable habitat over the core breeding range for forest specialist species the three-toed woodpecker Picoides tridactylus

The European breeding range of the three-toed woodpecker Picoides tridactylus overlaps with the distribution range of coniferous and mixed forests with domination of Norway spruce Picea abies or European silver fir Abies alba. The paper describes a new breeding site of the three-toed woodpecker in the Sobibór Forest, eastern Poland outside the distribution range of these two tree species and its relationship with Eurasian beaver Castor fiber. The birds occurred in dead alder forests and were recorded 3–4 years after forest started to decline due to the high level of surface waters associated with the keystone role of the beaver. The decaying cycle of trees was possible because the area settled by woodpeckers was protected as a nature reserve.

How Important are Nest Cavities Made by the Three-Toed Woodpecker Picoides tridactylus for Cavity-Nesting Forest Bird Species?

Woodpeckers are important primary excavators that produce nest-sites that are also used by several other cavity-nesting animals. However, the value of nest sites produced by different woodpecker species for other cavity-nesters is not generally known. We studied old Three-toed Woodpecker Picoides tridactylus cavities to examine their importance for other cavity-nesting forest bird species. Over a 31-year period (1987–2017), we annually monitored the occupancy of 655 cavities excavated by the Three-toed Woodpecker in 86 territories of the species in a 170-km2 area in southern Finland. Eight bird species used old Three-toed Woodpecker cavities for breeding, and the occupancy of these cavities by all secondary users was 21.3%. The expected mean number of lifetime occupancies by secondary cavity-nesters for a single cavity was 2.03. This is equivalent to a mean of two cavities occupied per territory per year, if we assume that Three-toed Woodpeckers produce a new cavity every year. The actual numbers of annually occupied cavities by secondary cavity-nesters can be substantially lower especially in territories that are not constantly occupied by the Threetoed Woodpecker. Based on the use of old cavities and densities of secondary cavity-nesting bird species, we conclude that cavities made by Three-toed Woodpeckers are most significant for the species itself, which accounted for 23.3% of nests in old Three-toed Woodpecker cavities. When Three-toed Woodpeckers reused an old cavity rather than occupy a freshly excavated cavity, 93% of cavities selected were originally excavated by Three-toed Woodpeckers. In addition, old cavities are important for the Pygmy Owl Glaucidium passerinum — up to 26–31% of breeding attempts were in old Three-toed Woodpecker cavities. The importance of old cavities for other hole-nesting bird species like the Pied Flycatcher Ficedula hypoleuca or the Great Tit Parus major was rather minor considering their densities within woodpecker territories.

Tree Sap as an Important Seasonal Food Resource for Woodpeckers: The Case of the Eurasian Three-Toed Woodpecker (Picoides tridactylus) in Southern Finland

The Eurasian three-toed woodpecker Picoides tridactylus is considered to be a specialist and obligatory insect-feeder, but the significance of other food sources for its survival and reproduction is unclear. We investigated the importance of tree sap as an alternative food source. We found that three-toed woodpeckers spent up to 33% of their foraging time and 38% of foraging events obtaining phloem sap from coniferous trees in spring before the start of their breeding. Sap use was most common in April and early May, and decreased significantly during nesting in late May and June. The woodpeckers made large numbers of new rows of sap holes in trees in the spring, the maximum being 399 fresh rows in 17 trees during one spring within a single territory. The sap trees were mostly at mature forest edges with rows oriented towards southern open areas indicating that woodpeckers utilized beneficial thermal conditions to obtain sap. These patterns suggest that sap is of high importance especially during the critical period of gaining energy for the start of nesting. We conclude that sap use is an important adaptation that may buffer variation in the availability of insect food in spring, and may increase the probability of three-toed woodpeckers commencing successful breeding.

Three-toed Woodpecker cavities in trees: A keystone structural feature in forests shows decadal persistence but only short-term benefit for secondary cavity-breeders

Abstract Primary cavity-producers like woodpeckers are often considered as keystone species, because they produce nest-sites also for several other cavity-nesting animals and, thus, maintain ecological webs of cavity-breeders. However, the detailed temporal dynamics of cavities and their lifetime occupancy rates and survival are not usually known which makes it difficult to assess the actual significance and full impact of primary cavity-breeders. In this study, we monitored cavities in a large forest landscape, covering the full lifetime of cavities. We focused on a mature and old-growth forest specialist cavity-breeder, the Three-toed Woodpecker Picoides tridactylus. The data include the annual occupancy history of 655 old cavities of the Three-toed Woodpecker in 86 territories in a 170-km2 area in southern Finland during 1987–2017. The study area included both managed and natural forest types. The median survival time of a cavity was 10 years, but there were significant differences between forest area types with a range of 7–13 years. The occupancy in all cavities was 21.3%, and the cavities were available for secondary cavity-breeders each year. There was a significant negative correlation between the occupancy and the age of the cavity. The first five years of a cavity were important for the total occupancy, and 86% of occupancies took place before the median age of the cavities. In cavities older than 15 years the occupancy was only 7%. The pattern was similar in all types of forests. Our results show that cavities made by Three-toed Woodpeckers have rather long lifespan but also that their active use by other cavity-breeding species is restricted mostly to few years only. The result indicates that new, fresh cavities are needed continuously in a forest landscape, in order to maintain the role that Three-toed Woodpecker has as a keystone species.

Predator discrimination and anti-predator behaviour by wintering parids: an experimental study

Even though birds’ perceptions of risk are biased towards starvation avoidance in winter, recognition of the level of threat of a predator is an important precondition. To investigate the ability of three tit species (Blue Cyanistes caeruleus , Great Parus major and Willow Tits Poecile montanus ) to recognise dangerous and harmless objects, I studied their mobbing reaction and the latency of the tits to return to the feeder after being exposed to life like models of Eurasian Sparrowhawk Accipiter nisus , Siberian Jay Perisoreus infaustus and Three-toed Woodpecker Picoides tridactylus , birds similar in size (about 30 cm) but differing widely from each other in feeding. The mobbing level was higher and the latency time of each of the tit species were significantly longer after presenting the Sparrowhawk than the Siberian Jay, whereas the woodpecker aroused no specific reaction. The tits apparently recognised the individual predator species and made decisions on their perceptions of the threat level.

The Importance of Nesting Cavity and Tree Reuse in the Three-Toed WoodpeckerPicoides tridactylusin Dynamic Forest Landscapes

Cavity-nesting birds can save time and energy by reusing old cavities. We studied cavity reuse and its connections to nesting success and timing in the three-toed woodpecker Picoides tridactylus in a 170-km2 area in southern Finland during 1987–2015. The data include 520 nest trees, 645 nest cavities and 833 nestings in 86 territory sites, including 211 cases of cavity reuse. Twenty-five percent of nestings was in previously used cavities. Twenty-eight percent of cavities and 25% of nest trees were used more than once. Reuse improved nesting success and facilitated early nesting in the year following first nesting. Reuse of nest trees with several cavities was observed in 15% of nest trees, and 62% of reused cavities were in those multi-cavity trees. Cavity reuse and multi-cavity trees were most abundant in long-term territories with stable habitats. In boreal forests, cavity and tree reuse can be an important adaptation allowing efficient nesting during a short breeding season.

Indicators of Forest Biodiversity: Which Bird Species Predict High Breeding Bird Assemblage Diversity in Boreal Forests at Multiple Spatial Scales?

Indicator species have been proposed to be used for revealing common status of ecosystems and their biodiversity. We studied breeding forest birds in southern Finland. Our aim was to find bird species combinations that would predict species richness of forest bird assemblages at several spatial scales. We evaluated statistical models that included 1–5 indicator candidate species, and ranked them according to the Bayesian information criterion. The red-breasted flycatcher Ficedula parva, the pygmy owl Glaucidium passerinum and the three-toed woodpecker Picoides tridactylus were found to be the best multiscale indicators. Models at smaller spatial scales, including several indicator species better explained the total variation in species richness. The indicators mostly revealed properties of the forest site rather than variation in species richness caused by species interactions. Our results show that a suitable set of indicator species may be a useful and quick method for the evaluation of bird diversity in forest environments.

北海道におけるミユビゲラ<i>Picoides tridactylus</i>の観察記録

北海道におけるミユビゲラ<i>Picoides tridactylus</i>の観察記録

Classical polyandry found in the three-toed woodpecker Picoides tridactylus

We report two cases of simultaneous, social polyandry in the three-toed woodpecker Picoides tridactylus found in Berchtesgaden National Park, Germany during an 11-year study. The first case was between two neighbouring pairs in 2003. A female incubated both of her clutches during a period of at least 8 days. The second case was in 2004 between a widowed male and a female of a neighbouring pair. This time, a female divided parental care between her two clutches during a period of at least 27 days. We hypothesise that social polyandry in the three-toed woodpecker may be linked to the parental quality of the first male.

Förekomst av tretåig hackspett Picoides tridactylus på bestånds- och landskapsnivå

The Three-toed Woodpecker Picoides tridactylus has declined with at least fifty percent in most of Sweden since the 1970s. This study was made in an area of 150 km2 in the eastern part of the province of UppIand in order to explain the habitat requirements of the species at the levels of both forest stand and landscape. The amount of dead wood was strongly correlated with the occurrence of the woodpecker. The stage of decay of the tree seemed to be more important than the tree species, both for feeding and nest site selection. All breeding sites were surrounded by continuous forests of 100–400 ha characterized by low management intensity (trees older than normal final felling age, little thinning, and several features typical for a "natural" forest). In control areas of similar size but with normal management regimes, we found the Three-toed Woodpecker rare or absent. We also found that a high proportion of swamp forest partly could compensate shortage of dead wood in other forests. The species is able to respond rapidly when suitable habitats with many dead or dying trees appear after a disturbance such as storm felling, insect attack, fire or flooding.

The Significance of Protected Areas for the Land Birds of Southern Finland

Protected areas (nature reserves) cover 0.7% of the land area in southern Finland (162,000 km2), which belongs to the south- and mid-boreal coniferous forest zones. The value of these areas in preserving land birds was studied on the basis of quantitative censuses. The numbers of bird pairs were estimated in nature reserves and in the whole of southern Finland, and the significance of the reserves was evaluated based on how large a proportion of the total population in southern Finland was found in them. Forest habitat generalists and species of coniferous forests occurred in protected areas as expected by the proportion of these areas in southern Finland. Specimens of these species groups comprise two thirds of all the country’s land birds. Species of old-growth forests and open peatlands clearly preferred protected areas, whereas species of bushes, and lush and deciduous forest were scarcer in protected areas than elsewhere in southern Finland. The latter fertile habitats are poorly represented in protected areas, even though due to their disappearance or alteration elsewhere several species confined to these habitats have declined and are even threatened. Drainage of open peatlands and clearcutting of old-growth forests has caused a decrease in the area of these habitats in southern Finland during the past decades. Therefore, protected areas have a high significance in preserving bird species preferring these habitats. Protected areas are particularly important for decreased species of old-growth forests, such as the Three-toed Woodpecker Picoides tridactylus and the Siberian Jay Perisoreus infaustus, as about 10% of their total population in southern Finland was estimated to breed in protected areas. The future protection of both old-growth and deciduous forests is important if we are to preserve bio-diversity of land birds in Finland. Las areas protegidas (reservas naturales) cubren 0.7% del area del sur de Finlandia (tamano 162.000 km2) que pertenece a las zonas de forestas de coniferas sud- y mesaboreales. Se estudio el valor de estas areas en la preservacion de aves terrestres sobre la base de sensos cuantitativos. Se estimaron los numeros de parejas de aves en las reservas naturales y en todo el sur de Finlandia, y se evaluo la importancia de las reservas basandose en la proporcion de la poblacion total del sur de Finlandia que representaban las aves que se encontraban en las reservas. Generalistas de habitats de forestas y especies de bosques de coniferas se encontraron en areas protegidas tal como era esperado en base a la proporcion de estas areas en el sur de Finlandia. Los especimenes de estos grupos de especies comprenden dos tercios de todas las aves terrestres del sur de Finlandia.

Stratification in Winter Feeding of the Great Spotted Woodpecker Dendrocopos major and the Three-Toed Woodpecker Picoides tridactylus

Stratification in Winter Feeding of the Great Spotted Woodpecker Dendrocopos major and the Three-Toed Woodpecker Picoides tridactylus