European Woodpeckers Research Articles

Observation of a Middle Spotted Woodpecker Dendrocoptes medius with aberrant, brown-coloured plumage

Abstract Birds with atypical colours in their plumage are not uncommon however, the potential causes of such aberrations have not been widely examined. Aberrant brownish-rufous phaeomelanin is one type of plumage colour that has been recorded in numerous bird species, including those which essentially contain only eumelanin (black) pigments, including several European woodpeckers. A Middle Spotted Woodpecker Dendrocoptes medius with aberrant phaeomelanised plumage observed in the Bükk Hills, Hungary, is detailed here and an evaluation of the possible nature of this form of plumage discussed.

Diversity of cranial shape in European Woodpecker species (Picidae)

Abstract The woodpecker family (Picidae) includes numerous species that vary in size and plumage colouration, but which share many easily recognisable external features. These birds possess pronounced anatomical adaptions that enable them to exploit arboreal habitats and live in niches that are inaccessible to most other birds. The aim of this study was to increase our knowledge on the relationships between skull shape, habitat preference, pecking abilities and foraging habits of 10 European woodpecker species. A geometric morphometric approach was used to analyse two-dimensional cranial landmarks. We used principal component (PC) analyses on those measurements that may be related to habitat preference and foraging habits. The PCs resulted in descriptions of the relative length and width of the bill, variation in its relative size, orientation of the nostrils variation in the elongation of the neurocranium, the relative size and position of the palatine bone, length of the rostrum, and the thickness of the mandible bone. The analysis showed and confirmed the presence of some cranial elements that are strongly associated with habitat preference, pecking behaviour and excavation abilities.

Foraging behaviour of the Great Spotted Woodpecker (Dendrocopos major) in the Białowieża National Park

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.

The Structure and Function of Drumming in the Middle Spotted Woodpecker Dendrocoptes medius

The disputed occurrence of drumming in Middle Spotted Woodpecker Dendrocoptes medius is due to a lack of sufficient, substantive evidence. In order to obtain a more reliable resource for assessing possible use of drumming in this species, breeding pairs were observed close to potential nest holes in south west France over five years. Drumming was heard in two of the six territories identified and sound recordings were made over four breeding seasons. Analysis of the recorded files consisted of counting and measuring intervals between strikes in all instrumental signals consisting of or containing drumrolls. The results showed that a form of drumming was performed but that it was infrequently produced in a discrete roll. It was usually soft and lacked the regularity of pattern found in the territorial drumrolls of other European woodpeckers. There was also a marked lack of consistency in the amplitude of strikes. As an acoustic signal, this study suggests its principal function to be a communication between partners in relation to the location and construction of a nest site.

Detection and identification of European woodpeckers with deep convolutional neural networks

Every spring, European forest soundscapes fill up with the drums and calls of woodpeckers as they draw territories and pair up. Each drum or call is species-specific and easily picked up by a trained ear. In this study, we worked toward automating this process and thus toward making the continuous acoustic monitoring of woodpeckers practical. We recorded from March to May successively in Belgium, Luxemburg and France, collecting hundreds of gigabytes of data. We shed 50–80% of these recordings using the Acoustic Complexity Index (ACI). Then, for both the detection of the target signals in the audio stream and the identification of the different species, we implemented transfer learning from computer vision to audio analysis. This meant transforming sounds into images via spectrograms and retraining legacy deep image networks that have been made public (e.g. Inception) to work with such data. The visual patterns produced by drums (vertical lines) and call syllables (hats, straight lines, waves, etc.) in spectrograms are characteristic and allow an identification of the signals. We retrained using data from Xeno-Canto, Tierstimmen and a private collection. In the subsequent analysis of the field recordings, the repurposed networks gave outstanding results for the detection of drums (either 0.2–9.9% of false positives, or for the toughest dataset, a reduction from 28,601 images to 1000 images left for manual review) and for the detection and identification of calls (73.5–100.0% accuracy; in the toughest case, dataset reduction from 643,901 images to 14,667 images). However, they performed less well for the identification of drums than a simpler method using handcrafted features and the k-Nearest Neighbor (k-NN) classifier. The species character in drums does not lie in shapes but in temporal patterns: speed, acceleration, number of strikes and duration of the drums. These features are secondary information in spectrograms, and the image networks that have learned invariance toward object size tend to disregard them. At locations where they drummed abundantly, the accuracy was 83.0% for Picus canus (93.1% for k-NN) and 36.1% for Dryocopus martius (81.5% for k-NN). For the three field locations we produced time lines of the encountered woodpecker activity (6 species, 11 signals).

Birdwatching, logging and the local economy in the Białowieża Forest, Poland

Birdwatching is one of the fastest growing subsectors of ecotourism, and can contribute substantial income to the local economy in areas with high bird diversity. The Bialowieza Forest (BF) is one of the most popular places to watch birds in Europe and is visited by thousands of birdwatchers every year. They are attracted by its particularly high diversity of bird species, many associated with the BF’s old-growth characteristics, including sizable populations of almost all European woodpeckers. These species are threatened by logging activities that are being undertaken on the assumption that forestry is important for the local economy. Our aim was to compare the revenue from birdwatchers with the revenue from other tourists visiting the BF to counter the economic justification for logging. Based on 165 responses to a structured questionnaire, our results show that one birdwatcher spends USD 64.6 per day on average, compared to USD 38.6 per day by other visitors to the BF. Birdwatchers also stay in the BF longer than other tourists (3.8 and 2.5 days on average, respectively). The total estimated local expenditure of approximately 14,000 birdwatchers in 2016 is almost USD 2.2 million. In contrast, since 2005, forest management and the sale of wood from the BF has led to economic losses each year, which we suggest would be further exacerbated by the impact of continued logging on birds and resultant inevitable decline in income from avitourism.

Differences in Habitat Requirements between Two SisterDendrocoposWoodpeckers in Urban Environments: Implication for the Conservation of Syrian Woodpecker

In numerous and extensive studies on birds in cities, woodpeckers have usually been neglected. Most research has only considered their suburban populations. Among European woodpeckers, only the Syrian Woodpecker Dendrocopos syriacus is synanthropic, occupying both rural and urban areas. In this study, habitat requirements of sympatric Syrian and Great Spotted D. majorWoodpeckers were investigated in two urban populations from central Poland. The occurrence of Syrian Woodpecker was found to be associated with walnut trees, fruit trees and mainly older softwood trees (poplars, willows). Plots with Syrian Woodpeckers were characterized by trees scattered among single-family buildings and within tenement houses in town centres. In contrast, plots with Great Spotted Woodpeckers were densely wooded, often with high share of hardwood trees and located in suburbs or residential woods. The aforementioned results show that these two sibling woodpeckers occupy different niches in urban populations. Moreover, this study supports the statement that urban areas are important for the Syrian Woodpecker in central Europe — a rare species in the European Union. Trees removal in cities, especially softwood trees, is a serious threat to the preservation of Syrian Woodpecker populations.

Monitoring of Artificial Nests in Horticultural Ecosystems-Observation of Woodpeckers Ethology

In order to increase the integrated protection of horticultural ecosystems by using the biological fight, the installation on artificial nests, is an important measure to help the insectivore birds. In a research program, a number of 166 artificial nets for Passeriformes birds were installed in different ecosystems as parks, botanical gardens and orchards in the South-Eastern part of Romania. During the nests monitoring period an interesting, but in the same time warring phenomenon, was noticed: a certain number of artificial nets were prayed by woodpeckers, especially by Dendrocopos major (Great Spotted Woodpecker). In Romania, all the ten European woodpecker species are nesting, nine being sedentary and one (Jynx torquilla) migratory, leaving the country in autumn. Woodpeckers in general, are very useful in woody plant biological protection, having a predominant insectivore nutrition and being the only one to keep under control the insects that are leaving on, inside and under the trees bark. The paper presents some data regarding the woodpeckers ethology in the studied ecosystems. More research are needed to understand the woodpeckers behaviour and to find protection methods of useful birds' nests against the woodpeckers attack. Keywords: useful birds; Dendrocopos major; Dendrocopos syriacus; Passer montanus; Picus viridis.

Postponed moult of primary coverts untangles the ageing of Wrynecks Jynx torquilla

ABSTRACTIn most bird species, all feathers are moulted at least once per year, usually after breeding (complete post-breeding moult). Woodpeckers (Picidae) often retain some primary coverts and secondaries during their otherwise complete post-breeding moult. To date, this phenomenon has received little attention and has not been studied thoroughly in European woodpeckers, even though it could prove very helpful for ageing and therefore for demographic studies. We studied the moult patterns of breeding adult Wrynecks Jynx torquilla in a Swiss Alpine valley between 2013 and 2016. Due to intensive ringing in the study area prior to the current study, our data set included birds of known age. Some individuals were captured and their moult documented in up to four years in a row. We found that Wrynecks present an extreme case of delayed primary-covert moult. No primary covert (PC) was renewed during the post-juvenile moult. At most three PCs were renewed by the second post-breeding moult and three to six at more advanced ages. That some juvenile PCs were retained until the sixth calendar year has not previously been documented for a species with such a relatively short lifespan. This principle of ‘postponed moult’ in Wrynecks affects the appearance of the PCs differently in each age class and allows us to age birds more accurately than previous methods. Here we describe how to interpret the moult pattern of PCs to age Wrynecks properly and argue that the moult strategy of Wrynecks was hitherto incompletely and in many cases mistakenly understood, leading to confusion in the ageing of Wrynecks.

Contrasting seasonal reactions of two sibling woodpeckers to playback stimulation in urban areas — implications for inventory and monitoring of the Syrian woodpecker

The Syrian woodpecker (Dendrocopos syriacus) is the most synanthropic species among European woodpeckers and can be considered to be a synurbic species benefiting from human activity and man-made habitats. Because it is closely related to the common great spotted woodpecker (Dendrocopos major), the interactions between the species should be investigated before conducting any study on the Syrian woodpecker. The aim of this study was to assess, analyse and compare both species reactions to the broadcasting of Syrian woodpecker playbacks throughout the year, in urban areas. The study was conducted in three Polish towns. All sites hosted populations of Syrian and great spotted woodpeckers living sympatrically. Both woodpeckers were observed throughout each year of study and responded to playback. The Syrian woodpecker more willingly responded to playbacks. Especially interesting was that the Syrian woodpecker female participated in territorial activity to a greater degree than males (sex-role reversed species). This is the first woodpecker study that shows a stronger territorial activity in females than males and the first reporting woodpecker reactions to playback stimulation throughout the year. The Syrian woodpecker is a rare and threatened species in Europe (protected under the Birds Directive of the European Union (2009/147/EC) and is considered a keystone species for woods and associated biodiversity in urban areas. Therefore, application of efficient methods for precise recognition of Syrian woodpecker territories (not only breeding ones) on the basis of correct interpretation of its behaviour is crucial for its conservation and urban habitat management.

Identification of European woodpecker species in audio recordings from their drumming rolls

Drumming sounds are substantial clues when searching audio recordings for the presence of woodpeckers. Woodpeckers use drumming for territory defence and mate attraction to such an extent that some species have no vocalisations for these functions. This implies that drumming bears species markers. This hypothesis stands at the root of our project to develop an autonomous program for the identification of drumming species. To proceed, we assembled a database of 361 recordings from open-access bird sound archives. The recordings were for nine drumming species found on the European continent. Focusing on the signal below 1500Hz, we reviewed all audio files and extracted 2665 drumming rolls. For recordings where multiple birds were present, the drumming rolls were attributed to individual birds. This allowed keeping track of the time interval between successive rolls. The characteristic traits of drumming are decidedly temporal. Consequently, the spectral features that have been successful in other recent bird identification studies were not applicable in our case. We developed specialized drumming parameters and automated their calculation. We then performed a t-SNE dimensionality reduction to visualise the dataset and to demonstrate that our parameters detached the different classes properly. Eventually, a k-NN algorithm accurately labelled 87.2% of the submitted test samples. The time structure within the drumming rolls (speed, acceleration) provided the critical features. The duration of the rolls followed in importance. The results compare well to existing literature and attest to the feasibility of monitoring European woodpecker species by tracking drumming.

Nest Site and Nest-Hole Characteristics Used by Great Spotted Woodpecker Dendrocopos major L. in Croatia

Great Spotted Woodpecker is the most abundant and widespread European woodpecker species, and it thus contributes the most to the number of excavated tree holes — an important habitat resource for secondary hole users. However, majority of nest site characteristics data comes from boreal and temperate forests, with lack of information from Southern Europe. In this article, nest sites of the Great Spotted Woodpecker have been investigated in the continental forests of Croatia — a previously understudied area of this species' range. A total of 41 active nest-holes found in the breeding seasons 2003 and 2004 are described. Nest-holes were mainly positioned below the crowns, in injuries of branch abscission. Nesting tree species were not used randomly: wild cherry Prunus avium in hill and pedunculate oak Quercus robur in riverine forests were preferred while hornbeam Carpinus betulus and maples Acer sp. were avoided. While tree species used for nesting vary across the Great Spotted Woodpecker range, and thus cannot be used as a uniform nest site predictor, defected wood spots on a tree, like scars of branch abscission, are identified as an important nest site clue and a habitat feature that is spatially more consistent. Nestholes' dimensions acquired in this research could not be clearly differentiated from those given for the other parts of the continent.

Reproductive correlates of eggshell thickness in European woodpeckers

Woodpeckers excavate their own nesting holes, have small eggs relative to their body size and many species have small clutches. Based on data from the eight European woodpecker species it was found that the mean thickness of eggshells increases with egg volume, whereas large woodpeckers lay smaller eggs with thinner eggshell relative to their body mass. It is speculated that woodpeckers minimize their reproductive costs by laying energy-poor eggs that are relatively cheap to produce, and with their low adult mortality rates, increase their lifetime reproductive success.

Nest site selection in middle and great spotted woodpeckers Dendrocopos medius & D. major: implications for forest management and conservation

Success of species conservation depends to a large extent on comprehensive management that considers all critical aspects of a species’ niche. Many studies have examined habitat factors in relation to occurrence, abundance or foraging behaviour of European woodpecker species, while relatively little is known about nest site selection. I compared habitat structures used for nesting by middle and great spotted woodpeckers Dendrocopos medius and D. major with available structures in an oak forest in the Swiss lowlands. I first tested if nest trees were randomly selected among available trees by focusing on species, condition and diameter of nest trees, and on the presence of the fruiting body (hereafter sporophore) of polypores (wood-decomposing fungi). Second, I examined if the nesting niches of the two species were differentiated. Both species showed strong preferences for oaks, large trees, dead trees and for trees with sporophores. Nest sites of the two species differed most strongly with respect to the presence of sporophores, cavity age and tree condition, pointing towards interspecific competition for nest sites. Old living or dead trees with sporophores are central components of the nesting niche of middle and great spotted woodpeckers. Conservation plans for the threatened middle spotted woodpecker have so far mostly focused on the needs in terms of distribution and foraging; future conservation strategies and forest management must take into account the preference for dead and decaying trees with sporophores as another vital resource. This will also provide benefits for other woodpecker species as well as for the community of secondary cavity nesters.

Population biology of European woodpecker species: a review

Understanding temporal dynamics of populations is important for the management of endangered and/or harvested populations as well as for evolutionary biology. Population sizes usually fluctuate over time because of changes in reproduction, mortality/survival, immigration and emigration. I reviewed the state of knowledge with respect to these vital demographic parameters on nine European woodpecker species. Only 4.2% of over 2100 publications found on these species reported on one or more of the vital rates, indicating severe knowledge gaps with respect to these traits. For most species, I found some information on reproduction (nest and fledging success), but generally much less on adult survival and immigration. No study quantitatively reported on emigration. No information on vital rates was found for Picus canus and Dendrocopos syriacus. Results are discussed in relation to geographic distribution and trends of the studied populations as well as with respect to life-history aspects and factors influencing vital rates.

NESTING AND FEEDING TREE SELECTION IN THE ENDANGERED WHITE-BACKED WOODPECKER, DENDROCOPOS LEUCOTOS LILFORDI

The White-backed Woodpecker (Dendrocopos leucotos) is one of the rarest European woodpeckers and its populations have declined markedly during the last century in many European countries. The objective of our study was to investigate the selection of nesting and feeding trees by the subspecies D. l. lilfordi, a field not previously investigated. We conducted this study in a mountain area of central Italy characterized by wide and homogeneous tracts of beech- (Fagus sylvatica) forested slopes. The rate at which we detected the species was highly correlated with the mean trunk dbh of the stand; the more mature the stand, the greater the number of woodpecker detections. The White-backed Woodpecker was dependent upon trees that were mature, dead, or in an advanced degree of decay for both nesting and foraging. The habitat specialization of the species suggests that forest stand management should promote longer harvesting rotations, preserve dead and decaying trees, create new foraging sites, and prevent excessive fragmentation of forested landscapes.

The effect of habitat loss on a deciduous forest specialist species: the White-backed Woodpecker ( Dendrocopos leucotos)

The White-backed Woodpecker ( Dendrocopos leucotos), one of the rarest European woodpeckers, is an old-growth deciduous forest specialist which has shown widespread decline over most of its distribution range. In this study, I extend earlier analyses concerning range contraction and explore whether there exists a threshold in the amount of suitable habitat below which the species will not persist, and if there is a nonlinear decline in population size as suitable habitat in the forest landscape is reduced. A metapopulation model was parameterized with data from a stable population and an analytical estimated extinction threshold was tested on two data sets on population decline and range contraction. The species disappears from regions when the amount of deciduous forest declines below a certain level. One isolated Swedish sub-population, which had withdrawn to a forest-landscape with resources below the habitat threshold, became extinct in 1996. The two other Swedish sub-populations are in forest landscapes below the minimum habitat threshold and both these populations are declining. Finnish sub-populations persist in a landscape below the habitat threshold, however. Reanalyzing data for Finland indicates a time delay in population response as habitat is destroyed and when the amount of suitable habitat falls below 10% there is an accelerated decline in population size. In today’s intensively managed forests in Sweden and Finland, with low proportions of suitable habitat in the forest landscape, the immediate danger for the species is that the population will suffer from isolation.

Foraging behavior of Black-backed and Three-toed woodpeckers during spring and summer in a Canadian boreal forest

During one spring to summer study in a Canadian boreal forest, Black-backed Woodpeckers (Picoides arcticus) were found to excavate mainly on logs and at the base of large-diameter tree trunks. In contrast, Three-toed Woodpeckers (Picoides tridactylus) preferred higher strata and smaller diameter trunks. The predominant foraging technique used by Three-toed Woodpeckers was bark scaling. Canadian Three-toed Woodpeckers showed foraging behavior similar to that found in European woodpeckers, but in the Nearctic range they have not fully developed the sap-licking behavior that is typical of the Three-toed Woodpeckers of the western Palearctic range.

Grauspecht-WeibchenPicus canus als Helfer an der Bruthöhle

In 1991 a second female Grey-headed WoodpeckerPicus canus rearing the young was recorded. This seems to be the first case of helping recorded in European woodpeckers so far. The conditions and advantages of helping and being helped are described with regard to the special situation of an isolated population in the north-west of Lower Saxony, Germany. Compared to other pairs in the east of Lower Saxony the pair with helper raised more offspring (4 vs. 1 young/breeding pair).

On the proper Generic Designation of the European Woodpeckers

On the proper Generic Designation of the European Woodpeckers