Habitat preferences of Picidae woodpeckers in the agricultural landscape of SE Poland: Is the Syrian Woodpecker Dendrocopos syriacus colonizing a vacant ecological niche? Jerzy MICHALCZUK* and Monika MICHALCZUK Department of Agrobiology and Environmental Protection, University of Rzeszów, Zelwerowicza 4, 35-601 Rzeszów, Poland *Corresponding author, J. Michalczuk, E-mail: [email protected] Received: 17. November 2014 / Accepted: 19. April 2015 / Available online: 07. April 2016 / Printed: June 2016
Abstract. In 2007 - 2009, we assessed the degree of colonization by woodpeckers in woods and trees of anthropogenic origin in the agricultural landscape of SE Poland. In order to determine the territorial boundaries of the birds (in an area of 305 km2), we used the mapping method combined with voice stimulation. The Great Spotted Woodpecker dominated in forests, present in 93% of territories found there, whereas the Syrian Woodpecker dominated in anthropogenic tree stands, occupying 90% of these territories. This species reached a density of 8.63 - 10.55 breeding pairs/10 km2 in anthropogenic tree stands. Low numbers of Great Spotted Woodpeckers also nest in this habitat. Densities of these species were 0.72 - 1.68 breeding pairs per 10 km2 of anthropogenic tree stands. Orchards made up the greatest proportion of Syrian Woodpecker territories at 53.5% and were the only type of tree stand preferred by this species. Parks made up a significant proportion (19.4%) of territories occupied by the Great Spotted Woodpecker, which were clearly favored only by this species. The habitat niches of these two species of woodpeckers overlap. The Syrian Woodpecker does not fully penetrate the available ecological niche of anthropogenic habitats, but compared to forest habitats, where the Great Spotted Woodpecker dominates, it encounters less competition there from native woodpecker species. As its primary competitor, this species is a potential biological barrier inhibiting the Syrian Woodpecker’s colonization of forests in areas of the sympatric occurrence of these two species. Therefore, anthropogenic tree stands are the main gateways and corridors of Syrian Woodpecker expansion in Europe. Key words: Picidae, Syrian Woodpecker, Great Spotted Woodpecker, habitat preferences, rural landscape.
Introduction Since the end of the 19th century, the Syrian Woodpecker has colonized much of Europe (BirdLife International 2004). It expanded in the south-eastern part of the continent (Cramp 1985, Munteanu & Samwald 1997, Zavialov et al. 2008, Michalczuk 2014), and has also reached Poland (Tomiałojć & Stawarczyk 2003, Michalczuk 2014). Although originally a thermophilic species inhabiting the forest communities of Asia Minor (Winkler 1973, Glutz von Blotzheim & Bauer 1980), the area of favourable habitat for the Syrian Woodpecker has increased recently due to the establishment of various types of anthropogenic tree stands, mainly orchards and other woodlots planted near housing estates (Mendelssohn & Yom-Tov 1999, Hatzofe & Yom-Tov 2002, AlSafadi 2004, Aghanajafizadeh et al. 2011). This species also colonizes tree stands inside human environment in Europe: parks, orchards, alleys and gardens, and its nests have even been detected in singly growing trees (Szlivka 1957, 1962, Ruge 1969, Cramp 1985, Michalczuk &
Michalczuk 2011, Ciach & Fröhlich 2013, Fröhlich & Ciach 2013, Michalczuk & Michalczuk 2015). It uses these areas throughout the year, avoiding dense forests, which it inhabits sporadically (Winkler 1971, Cramp 1985, Michalczuk & Michalczuk 2011). When colonizing new areas, this is probably done to avoid habitat competition with native woodpecker species, including the most common and most sociobiologically similar Great Spotted Woodpecker Dendrocopos major (Winkler 1971, Glutz von Blotzheim & Bauer 1980, Cramp 1985). Great Spotted Woodpecker and Syrian Woodpecker are also related genetically as they can hybridize (Kroneisl-Ruckner 1957, Skakuj & Stawarczyk 1994, Michalczuk & Michalczuk 2006b, Dudzik & Polakowski 2011, Michalczuk et al. 2014). The Great Spotted Woodpecker species is also very ecologically flexible and inhabits a variety of forested areas in Europe and Asia, as well as different types of tree cover in the agricultural landscape and cities (Cramp 1985, Mazgajski 1998, Salvati et al. 2001, Tomiałojć & Stawarczyk 2003, Myczko et al. 2014), where it can breed in sympatry with Syrian Woodpecker end
Habitat preference of woodpeckers in rural landscape
even hybridize (see works above). The study assessed the degree to which the Syrian Woodpecker has become part of the species assemblage of native woodpeckers inhabiting the agricultural landscape of SE Poland. To do this, we determined the extent of Syrian Woodpecker and Great Spotted Woodpecker in anthropogenic forests and tree stands, and identified their habitat preferences. Since native woodpeckers are primary competitors, they serve as a biological barrier in expansion of Syrian Woodpecker.
Material and methods Study area The study was conducted in south-eastern Poland, close to Tomaszów Lubelski (50o28'N, 23o40'E, Fig. 1). This area (approx. 305 km2) is characterized by undulating hills of 195-263 m above sea level (Kondracki 2000). The agricultural landscape dominates, comprised predominantly of crops (71%) and meadows (11%), whereas small forests represent only 4% of the area. These are mostly made up of hornbeam complexes, with a substantial share of Common Hornbeam Carpinus betulus and Oak Quercus sp., and conifer stands with a predominance of Scots Pine Pinus sylvestris. The anthropogenic tree stands accompanying build up areas preferred by the Syrian Woodpecker (Cramp 1985, Michalczuk & Michalczuk 2011, Michalczuk & Michalczuk 2015), comprise approximately 14% of the area (ca. 41.7 km2). They consist mainly of single trees, alleys, rows of trees and parks, and are dominated by Willow Salix sp., Poplar Populus sp., Maple Acer sp. and Ash Fraxinus sp. Apples Malus domestica, Cherries Prunus cerasus, Plums Prunus sp., and Walnuts Juglans regia are the main species of orchards. Rarely are conifers, such as Spruce Picea sp., Larch Larix sp. or Pine Pinus sp., found in the anthropogenic tree cover. Assessment of the number of woodpeckers The search for woodpeckers was conducted by the mapping method with the use of voice stimulation (Michalczuk & Michalczuk 2006a, 2006b). The search was carried out mainly in anthropogenic afforestations (41.7 km2), as well as in forests adjacent to residential buildings, where the Great Spotted Woodpecker is most often found, but these habitats can also be occupied by the Syrian Woodpecker (Glutz von Blotzheim & Bauer 1980, Cramp 1985, Kurek 1984). In each seasons 2007-2009, over six field controls were conducted in whole entire study area. Counting was carried out mainly along roads, with voice stimulation and listening for birds performed at 200-400 m intervals. The voice stimulation consisted of a five minute sequence of Syrian Woodpecker calls and drumming. The stimulation was immediately discontinued when a woodpecker reacted. In the absence of a reaction, we listened for about one minute, and then moved on to the
15 next point where stimulation was continued (Michalczuk & Michalczuk 2006a, 2006b). The same territory search method was used for Great Spotted Woodpeckers, which also actively responded to the voice stimulation of the Syrian Woodpecker. The sites where birds were found were noted on a 1:25 000 or 1:10 000 scale topographic map. The sex of the birds and their individual plumage characteristics were registered, as well as direction from which the bird flew. In distinguishing neighboring territories, important information was gained when simultaneously identifying individuals from neighboring pairs. In the case of both these species, at least one additional confirmation of pair sighting, or alternating male and female, was required. One case of mixed pair of the Great Spotted Woodpecker’s male and Syrian Woodpecker’s female was included only for comparison of both these species habitat preferences in forest and anthropogenic tree stands (see method below) as Syrian Woodpecker site. Breeding sites were also located on the basis of detected nests (average nest detection about 50%, e.g. Michalczuk et al. 2011). Over six controls in each year of the study area from March to July were taken to enable an accurate demarcation of the birds’ territories. Territorial boundaries were determined by connecting the maximally distant points where the birds of a given breeding pair were observed. After counting the birds, we calculated the density of breeding pairs of each species for the total surface area of the study area, as well as for the area of anthropogenic tree cover (Table 1). Assessment of woodpecker habitat preferences To determine the degree of using anthropogenic tree cover and forests by the closely related species of Syrian Woodpecker and Great Spotted Woodpecker, an area designated as “PL” was distinguished within the study area. 157 km2 in size, it was located in the northern part of the study area (Fig. 1). In addition to anthropogenic tree cover, it included 6 forested sites with a total area of 380 ha (Fig. 1). The size of individual forests varied from 11 to 164 ha (mean of 63.2 ha; 1SD: 55.2, N = 6). The main objective of the 2007 counts conducted in forest area "PL" was solely to assess the number of Syrian Woodpecker and Great Spotted Woodpecker territories occupied by pairs or single individuals without determining their breeding status. This made it possible to assess the scale of anthropogenic tree cover use and forest use by these quite sociobiologically similar species (Winkler 1971, 1973, Glutz von Blotzheim & Bauer 1980). To this end, two counts were conducted in all types of tree cover in the entire "PL" area during the pre-breeding period (March-April). The methodology of searching for woodpecker territories was similar to the previously described and based on the recommendation of combining the cartographic method with voice stimulation (Michalczuk & Michalczuk 2006a, 2006b). Voice stimulation was conducted in forested areas in a grid of points, spaced approx. 200-400 m. Voice stimulation of five minutes duration was performed with one minute of listening at each point. The location of a bird was recorded on a 1:5 000 scale map, and then we moved to the next point, where the search continued.
J. Michalczuk & M. Michalczuk
Figure 1. Distribution of breeding sites of Picidae woodpeckers in the study area in 2007 - 2009. Key: 1 - areas of dense residential buildings, 2 - forests dominated by the Great Spotted Woodpecker D. major, 3 - main roads, 4 - fields and meadows, A - boundaries of the study area, B - boundaries of the “PL” supplemental area, breeding sites: ○ – Syrian Woodpecker, ■ – Great Spotted Woodpecker. Table 1. Habitat preferences of woodpeckers in relation to different types of anthropogenic trees stands in the agricultural landscape of SE Poland. Key: p.t. – proportion of trees, s.i. – selection index. tree stand
Great Spotted Woodpecker
tree row and alley
After the counts, we calculated the number of territories occupied by the woodpeckers in forests and anthropogenic tree cover. During the study, we also assessed the type of tree cover in anthropogenic habitats used by the Great Spotted Woodpecker and Syrian Woodpecker. To this end, we randomly selected points from which the tree stands were assessed in all the territories of the Greater Spotted Woodpecker (N = 15) and in 28 randomly selected territories of the Syrian Woodpecker. In order to determine the size of specific territories, maps were used at a scale of 1:5 000. On each territory map 100 points were randomly selected, and then each was located in the study area. In a lot of the points there were treeless habitats like fields and meadows. When a tree was found at a designated point, it was categorized by type of stand: alley or row of trees, cemetery, tree clump, park, single
tree and orchard. Only sites with trees having a diameter of greater than 15 cm, measured 1.3 m from ground level were assessed, as trees of such dimensions are used for the excavation of nest holes by woodpeckers, such as, for example, the Syrian Woodpecker (own observation). In this way, 20 to 45 tree assessment points were randomly selected in specific territories and used to calculate the proportion of specific types of tree cover within each territory of the birds. In this manner, 366 tree assessment points were described for the Great Spotted Woodpecker and 657 points for the Syrian Woodpecker (Table 1). The randomly selected points were also used to identify the habitat preferences of the woodpeckers. To this end, the share of individual types of tree cover located within all the territories of the various woodpecker species were compared to their availability in the study area. An assessment of anthropogenic tree
Habitat preference of woodpeckers in rural landscape
cover in the study site was performed using the same method. To do this, the study area was traced on 45 maps scaled at 1:10 000, each covering an area of approximately 10 km2 (4.0 to 2.5 km). On each map 100 points were randomly selected, which were then located in the field. When trees with diameter of >15 cm were observed at these points, they were assigned to the aforementioned categories of tree stands. In this way, the types of tree stands were identified for 323 points, which allowed us to determine the proportions of specific types of tree stands in the study area. To assess the habitat preferences of woodpeckers to particular types of tree stand, we used individual selection indices (Manly et al. 1993). This is the quotable of the share of each type of tree stand found in the territories of the birds divided by their proportion in the study area. Based on the Bonferroni inequality for individual selection indices, 95% simultaneous confidence limits (95% CL) were constructed. If the resulting confidence interval was greater than 1, this meant that the type of stand was preferred. When it was less than 1, this indicated that the woodpeckers avoided this particular type of tree stand. Confidence intervals of individual selection indices with a value of 1 meant the lack of woodpecker preference to the tree stand category. Negative lower limits of the confidence intervals were changed to 0.00, as negative values of the confidence intervals are not possible. The chi-square test, Mann Whitney U test and Kruskall-Wallis test with the Dunn post-hoc test were used for the statistical analysis, which was performed using Excel and the StatisticaSoft 7.1 GB package. Statistical differences were accepted at a significance level equal to or lower than 0.05. We also calculated the width of the habitat niches occupied by each species (Levins 1968). For this, we used the following formula: B=
1 , pi2
where: B – index of the habitat niche width, p – share of „i” in the habitat niche. To calculate the degree of niche overlap between the habitats of the species, Schoener's index (1968) was used: OI=1-1/2∑(pxi-pyi), where pxi and pyi represent the frequency of tree cover category „i” in the territories of specific species of woodpeckers x and y. OI is the variable from 0 (no overlap) to 1 (complete coverage), and niche overlap is accepted as significant if the value of the index exceeds 0.60 (Wallace 1981).
17 km2 of anthropogenic tree stands), the density of breeding pairs ranged from 8.63 to 10.55/10 km2. The Syrian Woodpecker dominated among woodpecker species in anthropogenic tree stands, where it represented approximately 89% (range in each year’s 86 - 91%) of the breeding population of all nesting woodpecker species found. In specific sites, most often 1 - 2 breeding pairs of this species were confirmed, and only exceptionally were up to 4 breeding pairs detected in the largest villages. However, there were also sites where no breeding birds were confirmed (Fig. 1). Each season, the Great Spotted Woodpecker was also noted at 4, 7 and 4 locations. The average density of breeding sites ranged from 0.13 to 0.23 pairs /10 km2 of study area and 0.96 - 1.68 pairs/10 km2 of anthropogenic tree stands. The proportion of this species in the breeding assemblage of woodpeckers averaged 11%. The habitat preferences of woodpeckers During the census conducted in 2007 of the "PL" area, clear differences were found in the habitat preferences of both species of woodpeckers (χ2 = 46.02, df = 1, p < 0.0001, Fig. 2). The Syrian Woodpecker dominated in the anthropogenic tree stands, with 35 territories (90% of territories). The Great Spotted Woodpecker had only 4 territories in this habitat, mostly located near parks. The proportion of the occurrence of both these species in forests was the opposite. This is where the Great Spotted Woodpecker dominated, occupying 27 territories (93% of territories). The Syrian Woodpecker clearly avoided forests, as it was
Results Distribution and number of woodpeckers In 2007 - 2009, the population Syrian Woodpeckers was estimated respectively at 44, 42 and 36 pairs. Its density ranged from 1.18 to 1.44 breeding pairs per 10 km2 of study area. Taking into account only the area of optimal habitat for this species (41.7
Figure 2. Habitat preferences of the Syrian Woodpecker (white area) and Great Spotted Woodpecker (grey area) in the “PL” supplemental area in 2007. The values over the columns represent the number of noted territories.
J. Michalczuk & M. Michalczuk
Figure 3. Average percentage of specific types of tree stands in Syrian Woodpecker (grey, N = 28) and Great Spotted Woodpecker (white, N = 15) territories located in anthropogenic tree stands (vertical lines – standard errors, * - p < 0.005, ** - p < 0.0005).
confirmed here on only two territories (Fig. 2). In one case it was a mixed pair of the Great Spotted Woodpecker’s male and Syrian Woodpecker’s female. The proportion of specific tree stand types in Syrian Woodpecker territories was diverse (H = 129.32, df = 5, p < 0.0001, Fig. 3). Orchards were most frequently reported (mean 53.5%, 1SD: 16.1), as well as alleys and rows of trees (mean 30.1%, 1SD: 9.6), but the difference in the share of these categories was not found to be statistically significant. Both of these types of tree stands, however, occurred significantly more often than other categories (Dunn's test p < 0.0001 respectively for all categories). Clumps of trees, which accounted for 10.0% (1SD: 10.3), were avoided by the birds. Only orchards were preferred by the Syrian Woodpecker (Table 1). Alleys and tree rows, parks (mean 1.9%, 1SD 5.1), cemeteries (mean 0.4%, 1SD: 1.3) and single trees (mean 4.2%, 1SD: 4.5) were used by the species according to their availability in the study area (Table 1). Alleys and tree rows, however, were avoided by the Great Spotted Woodpecker (Table 1), and an average share in its territories of 18.3% (1SD: 12.2, Fig. 3). The Great Spotted also avoided orchards, which accounted for an average of 28.0% (1SD: 22.1, Fig. 3). This species preferred only parks, which accounted for 19.4% of the territories (1SD: 18.5, Fig. 3). Clumps of trees were significantly represented among the territories of the Great Spotted Woodpecker (mean 31.3%, 1SD: 16.4). However, as with other categories of tree
stands, they were used according to their availability in the study area (Table 1). Single trees represented only 1.6% (1SD: 3.0), and cemeteries 1.3% (1SD: 3.0, Fig. 3) of tree stand types with Great Spotted Woodpecker territories. The differences among the share of particular tree stand categories of Great Spotted Woodpecker territories was statistically significant (H = 44.99, df = 5, p < 0.0001, Fig. 3). The categories of parks, clumps of trees and orchards were reported significantly more often than cemeteries (post hoc Dunn's test p = 0.0370), while clumps of trees and orchards were noted more frequently than single trees (post hoc Dunn's test p < 0.0001). Tree clumps (Mann Whitney U test Z = -3.87, p = 0.0001) and parks (Mann Whitney U test Z = 2.90, p = 0.0037) were significantly more often represented in the territories of the Great Spotted Woodpecker than in Syrian Woodpecker territories. Alleys and tree rows (Mann Whitney U test Z = 2.93, p = 0.0034) as well as orchards (Mann Whitney U test Z = 3.50, p = 0.0005) are significantly more often noted as the sites of Syrian Woodpecker territories. The Great Spotted Woodpecker used a broader range of habitat niches (B = 4.02) than the Syrian Woodpecker (B = 2.50). The Syrian Woodpecker’s habitat niche overlapped with that of the Great Spotted Woodpecker (OI = 0.70)
Discussion The density of Syrian Woodpecker breeding pairs in the agricultural landscape of the study area was
Habitat preference of woodpeckers in rural landscape
at levels characteristic of south-eastern Poland. In the area of Tomaszów Lubelski, this species reaches a density ranging from 0.8 to 2.1 breeding pairs per 10 km2 (Michalczuk & Michalczuk 2006a, Michalczuk et al. 2011, Michalczuk & Michalczuk 2015). Similar findings were reported in the municipality of Żurwica (near Przemyśl), where a density of 1.6 - 2.1 pairs/10 km2 was noted. However, when calculated for the area of optimal habitat for this species (the tree stands found in rural villages), it reached a range of 14.8 - 19.5 pairs/10 km2 (Hordowski 1998). The Syrian Woodpecker density in optimal habitats of the study area was close to the lower range of densities for the agricultural landscape of this part of Poland (range of 5.5 - 20.0 pairs/km2, Michalczuk & Michalczuk 2006a, Michalczuk et al. 2011, Michalczuk & Michalczuk 2015), and reflect a drop in the Syrian Woodpecker population of the Tomaszów Lubelski area in recent years (Michalczuk et al. 2011, Michalczuk & Michalczuk 2015). The density of the Great Spotted Woodpecker obtained during the study confirms their sporadic nesting in anthropogenic habitats (Cramp 1985, Tomiałojć & Stawarczyk 2003, Kujawa 2006). Although locally, i.e. in small parks or other dense tree stands in the agricultural landscape, woodpeckers can reach densities similar to those found in forests (Bednorz et al. 2000, Tomiałojć & Stawarczyk 2003, Kosiński & Kempa 2007, Tryjanowski et al. 2009), their concentrations in large areas of the agricultural landscape with a low proportion of forests are smaller. For example, in the agricultural landscape of Wielkopolska (near Turew in W Poland), the density of the Great Spotted Woodpecker was estimated at 2.0 pairs/10 km2 (Kujawa 1994). These values are higher than results obtained in this study. Probably it’s a result of four times higher (15%) forests share in the study area near Turew, than in the studied area in SE Poland (about 4%). However, it can’t exclude that so high density of Great Spotted Woodpeckers in allopatric population may come from absence of Syrian Woodpeckers in the North-West part of Poland (Michalczuk 2014). The absence of the Syrian Woodpecker as main competitor enable Great Spotted Woodpecker to inhabit spread anthropogenic afforestations in North-West part of Poland. Some authors (eg. Fröhlich & Ciach 2013) suggest that the Syrian Woodpecker inhabits an
19 ecological niche devoid of other woodpecker species. However, this was not confirmed in studies conducted in south-eastern Poland. While the Syrian Woodpecker clearly dominated in the agricultural landscape, and its abundance was ten times higher than that of the Great Spotted Woodpecker, the presence of this species in anthropogenic habitats unequivocally indicates that colonizing new areas the Syrian Woodpecker penetrates only a partially vacant ecological niche. Such conclusions can be drawn by analyzing data from the former Vojvodina and Austria, where in addition to the Syrian Woodpecker, the Great Spotted Woodpecker also had territories in anthropogenic tree stands (Szlivka 1957, Ruge in 1969, Winkler 1973). This fact is also confirmed by observations from central Ukraine, where until recently, tree stands in human settlements were used quite extensively by the Great Spotted Woodpecker. After colonization of these areas by the Syrian Woodpecker, the Great Spotted Woodpecker retreated to the densest tree stands in river valleys, parks and woodlots (Mitjaj 1986). Such a dependence was also seen in the study area, where forests were dominated by the Great Spotted Woodpecker, considered the main competitor of the studied species, since both are characterized by a similar ecology and biology (Winkler 1971, Glutz von Blotzheim & Bauer 1980, Cramp 1985) and can form mixed pairs, which was found in the study area and in other places in Poland (Dudzik & Polakowski 2011). Taking into account the fact that the both species can hybridize (Kroneisl-Ruckner 1957, Skakuj & Stawarczyk 1994, Michalczuk & Michalczuk 2006b, Dudzik & Polakowski 2011, Michalczuk et al. 2014), it is uncertain which and how many individuals are genotypically “pure” (e.g. Michalczuk et al. 2014). Similar social behaviors (Winkler 1971, 1972) result in the Syrian Woodpecker’s general avoidance of forests when colonizing new areas because it is not able to overcome the barrier of the equally ecologically flexible Great Spotted Woodpecker. The greater diversity of woodpecker species composition and their greater densities in forests compared to anthropogenic habitats (Bednorz et al. 2000, Tomiałojć & Stawarczyk 2003, Kosiński & Kempa 2007) probably has a significant impact on directing the Syrian Woodpecker’s colonization to tree stands in the immediate environment of humans, as these are usually avoided by woodpeckers. Studies have shown that both closely related
20 woodpecker species also largely avoided each other within anthropogenic habitats. Although the habitat niches of these two species overlap, this study clearly indicated a clear division of site use between the two species in areas of their sympatric occurrence. Great Spotted Woodpeckers had territories in the densest tree stand categories, such as in parks and tree clumps, often inhabited by this species in the agricultural landscape (Tomiałojć & Stawarczyk 2003, Tryjanowski et al. 2009). Orchards clearly dominated as the territories of Syrian Woodpeckers, which are often readily chosen by them (Szlivka 1957, 1962, Ruge 1969, Michalczuk et al. 2011, Michalczuk & Michalczuk 2015). Preference for orchards may be related to the nutritional requirements of the Syrian Woodpecker. This species widely forages on fruits and seeds, and is the only European woodpecker to feed these items to their chicks (Cramp 1985). It also often produces nest holes in fruit trees (Szlivka 1957, 1962, Ruge 1969, Cramp 1985), which grow mainly in orchards found in close proximity to humans. The study area’s anthropogenic tree stands were also inhabited by other potential competitors of the Syrian Woodpecker, such as the Wryneck (own observation). Other species also readily use nest holes after the Syrian Woodpecker, such as the Starling Sturnus vulgaris (Szlivka 1957, 1962, Michalczuk et al. 2011). This common secondary hole nester can vigorously compete for tree holes with primary hole nesters (e.g. Koenig 2003, Wiebe 2003), including the Syrian Woodpecker (Szlivka 1957, 1962, Michalczuk et al. 2011, Michalczuk & Michalczuk 2016). However, anthropogenic tree stands as habitats with less competitive pressure from native woodpecker species, especially the closely sociobiologically related Great Spotted Woodpecker, are the main gates and corridors of Syrian Woodpecker expansion in its colonization of new areas of Europe.
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