The Oriental White Stork (Ciconia boyciana) is a large and endangered waterbird in East Asia. Research on conservation genetics of this species is urgently needed. In this study, microsatellite marking technology was used for screening and analysis of genetic diversity of microsatellite markers in Oriental White Storks. A total of 36 pairs of microsatellite primers were used, of which 7 pairs came from Ciconia ciconia, 12 pairs from Nipponia nippon and 17 pairs from Ardea herodias. Microsatellite loci were screened from 23 individuals of the Oriental White Stork and 11 microsatellite loci were found with high polymorphism. The number of population alleles ranged from 3 to 11, averaging 7.09. The average expected heterozygosity (He) was 0.7816 and the average polymorphism information content (PIC) 0.7172, suggesting a relatively high genetic diversity in the population.
However, the above knowledge presented about Syrian Woodpecker preferences is based on studies conducted particularly in the anthropogenic tree stands of Europe, which were colonised by this species mainly in the XX century (Glutz von Blotzheim and Bauer, 1980; Cramp, 1985; Michalczuk, 2014). Most studies were conducted in cities, towns and rural landscapes, but none in forests (e.g., Szlivka, 1957; Ruge, 1969; Michalczuk and Michalczuk, 2016a; Figarski and Kajtoch, 2018; Michalczuk, 2020). There are not many publications providing information about the habitat requirements of the Syrian Woodpecker in the primary distribution range and primeval habitats of this species, which are the forests of Southwest Asia (Glutz von Blotzheim and Bauer, 1980; Cramp, 1985; Aghanajafizadeh et al., 2011; Mohamadian et al., 2019a). Additionally, in this part of Asia this species occurs sympatric with the Middle Spotted Woodpecker, and they inhabit natural mountain forests (Glutz von Blotzheim and Bauer, 1980; Cramp, 1985; Winkler et al., 1995; Mohamadian et al., 2019b). Although previous studies of Middle Spotted and Syrian Woodpeckers were carried out generally in Europe, the understanding of how these two woodpecker species select habitats requires knowledge acquired across different localities in the whole range of the species. The assessment of habitat preferences of the Middle Spotted and Syrian Woodpeckers in Southwest Asia may contribute to the identification of forest features that are important for their conservation in this region, as well as in other places.
The aim of this research was to obtain information on forest features that can influence the nest site selection and habitat preferences of Middle Spotted and Syrian Woodpeckers in the natural mountain forests of Southwest Iran. For this purpose, the selected nest tree features were compared to attributes of trees located in the vicinity of the nest trees, trees that occurred in breeding pair territories, and also those located outside the breeding pair territories. To characterise habitat preferences of the two mentioned woodpecker species, the characteristics of nesting, territory, and outside territory tree stands, were compared. The identification of forest features that determine the occurrence of these two species may deliver important information about their habitat requirements. Research results can also help indicate forest areas crucial for their conservation, and develop important forest management principles to aid preserving the habitats of these species.
2.
Materials and methods
2.1
Study area
The study area is a natural forest located around the city of Yasuj in southwestern Iran (31°48′ N, 51°42′ E) and consists of four subplots: W1 (10.0 km2), W2 (3.5 km2), W3 (3.1 km2) and W4 (2.3 km2), 2000–2200 m above sea level (Fig. 1). Annual rainfall averages 817 mm and the average annual temperature is 14 ℃. We worked in two types of forest stands. Study plot W1 was a multispecies forest, at a higher elevation above sea level than the other three subplots, with habitats consisting of shrubs of the genera Acantholimon, Amygdalus and Astragalus and three dominant tree species: Mount Atlas Mastic (Pistacia atlantica), Ash (Fraxinus angustifolia) and Wild Pear (Pyrus glabra). Other tree species were less common in this subplot (Table 1; Appendix Fig. S1). In subplots W2–W3, the forest habitat was dominated by Oaks (Quercus brantii var. persica), which represented up to 99 % of trees in stands (Appendix Fig. S2). Only occasionally in these tree stands Mount Atlas Mastic and Ash were noted (Table 1). Our plots are not part of the Department of Environment (DoE) protected areas. They are only patchily and occasionally harvested for local timber use. The main disturbances (naturel or anthropogenic) in the study area are timber harvesting and forest fires. In the past 20 years, there have been intentional and accidental wildfires, both large and small, due to road construction within the forest. These wildfires have resulted in a significant portion of the entire forest burnt including canopy trees for several days. Plowing for cultivation, oak declining disease, recent droughts and uncontrolled nighttime charcoal harvesting and sales have led to the drying out of a significant number of weakened trees. The local population rapidly harvests these weak or semi-dry trees as charcoal.
Figure
1.
Location of the study area in SW Iran and distribution of four woodpecker subplots (W1–W4) near Yasuj city. Denotations: rectangle with dotted line – study area; rectangles with solid line – woodpecker subplots W1–W4; grey dots – nest tree stand plots; TSP – study pattern of the tree stand plot (10-m circle with solid line – sample plot for trees' measurements; 50-m circle with dashed line – sample plot for tree crown cover evaluation, for more details see Materials and Methods).
Table
1.
Tree species composition of tree stands in natural forest of SW Iran.
Tree species
Nest trees–NT
Trees in the vicinity of nest trees–TV
Trees in nest tree stands–NTS (NT+TV)
Trees in territory tree stands–TTS
Trees outside the territory tree stands–OTT
Tree stands total–TPT (TTS+OTT)
Syrian Woodpecker
Acer (Acer monspessulanum)
–
8.2 (6)
5.8 (6)^
4.2 (3)^
5.4 (4)
4.8 (7)
Ash (Fraxinus angustifolia)
30.0 (9)*
9.6 (7)
12.6 (13)^
28.2 (20)^
32.4 (24)
30.3 (44)
Honeysuckle (Lonicera nummularifolia)
–
8.2 (6)
5.8 (6)^
4.2 (3)^
2.7 (2)
3.4 (5)
Dotted Hawthorn (Crataegus puntica)
–
4.1 (3)
2.9 (3)^
8.5 (6)^
1.4 (1)
4.8 (7)
Mount Atlas Mastic (Pistacia atlantica)
60.0 (18)*
38.4 (28)
44.7 (46)*
32.4 (23)^
17.6 (13)
24.8 (36)
Oak (Quercus brantii var. persica)
–
2.7 (2)
1.9 (2)^
4.2 (3)^
6.8 (5)
5.5 (8)
Wild Pear (Pyrus glabra)
10.0 (3)^
28.8 (21)
23.3 (24)^
18.3 (13)^
31.1 (23)
24.8 (36)
Willow (Salix excelsa)
–
–
–
–
2.7 (2)
1.4 (2)
All trees
30
73
103
71
74
145
Middle Spotted Woodpecker
Ash (Fraxinus angustifolia)
–
–
–
0.8 (1)
–
0.4 (1)
Mount Atlas Mastic (Pistacia atlantica)
–
0.9 (1)
0.8 (1)^
0.8 (1)^
0.9 (1)
0.9 (2)
Oak (Quercus brantii var. persica)
100.0 (16)^
99.1 (106)
99.2 (122)^
98.6 (118)^
99.1 (106)
98.7 (224)
All trees
16
107
123
120
107
227
Percentage share and number of cases (in brackets) of specified tree stands described for studied woodpecker species. *–tree species preferred by woodpeckers; ^–tree species not preferred by woodpeckers; studies did not identify tree species avoided by woodpeckers (evaluation done according to Manly selection index – for details see Materials and Method).
We assessed the nest distribution of the studied woodpecker species in subplots W1 during 2015–2017 and in subplots W2–W4 during 2017–2018 (Fig. 1). For this purpose, a nest searching method was used. We did not use playback in the field surveys. We began to search for active nests from late March to mid-May in a survey on parallel lines by 2–4 people on foot (6 h per day and up to 20 ha). To find nest cavities, almost all potential nest trees in the area were inspected. Estimated territories were determined by watching pairs at the beginning of the breeding season. A more intensive following at this time led to the location of some of the nests. Active nests of the woodpeckers were found according to the sound of excavation, signs of scratching and tree excavating, woodpeckers entering and leaving the nest or observation of wood chips on the ground under the tree. In the breeding stages in some cases we also found eggs or nestlings within the nests. The location of the nests was then determined with a handheld GPS logger.
2.3
Description of nest trees and nest tree stand plots
Nests and nest trees were described after the woodpecker breeding season. For each tree, its species and tree diameter at breast height (DBH) was measured 1.3 m above the ground level using forest callipers (Table 1; Appendix Table S1). Furthermore, the health condition of the tree was also assessed. For this purpose, a seven-point scale was used, where the lowest note (1) was attributed to healthy trees in good health condition. The higher notes were dedicated to: declining (2), weakened (3), sick (4), dying (5), and fresh dead trees (6). The highest note (7) was dedicated to dead trees with soft wood (for details see Michalczuk and Michalczuk, 2020a; 2020b, 2022; Appendix Table S2). The localisations in nesting trees were assigned to two different categories: cavities located in the trunk and cavities located in the branches. During the research, we also assessed the share of reuse of nest trees by both studied species. For this purpose, trees with old nests made by woodpeckers in previous seasons were controlled to see whether they were re-occupied by breeding pairs.
The 'nest tree' stands included the nest tree and the trees within a 10-m radius, were also described. Within each circle plot, we measured trees with DBH ≥10 cm, and we identified the species and health conditions, as they determine site choice by woodpeckers (e.g., Pasinelli, 2007). For trees located in such a plot, analogous measurements were performed: tree species, DBH and health condition on a seven-point scale (see above). For the stands were also evaluated: number of trees (1), number of tree species (2), average health condition (3), average DBH (4), cumulative basal area of the tree trunks (5) and the presence (yes/no) of trees which included old woodpecker cavities (6). Using QGIS software and the updated nest tree point layer from a handheld GPS logger, the tree crown cover in the vicinity of the nest tree was also assessed (7). For this purpose, using the satellite map available on the Google Earth server (https://www.opengee.org/) and the polygon layer, the range of tree crowns was delineated. This was done in a 50 m radius around the nest tree vicinity (Fig. 1). Then the percentage share of the tree crown cover was assessed in the polygon (0.785 ha) for each nest tree stand.
2.4
Designation of territory and outside territory for tree stand plots
We implement all woodpecker nest tree locations as a point layer in QGIS software (QGIS, 2019). The particular nest tree locations of Syrian and Middle Spotted Woodpeckers allowed us to examinated of tree stands in the territories for these two species. For this purpose, we used the satellite image available on the Google Earth server. In our study, we assumed that nest trees were the centres of the woodpecker territories. The closest distance between the neighbouring nest trees that were used by woodpeckers in a particular breeding season was then measured. The medians of this measurement for the Syrian and the Middle Spotted Woodpeckers were respectively 226 (n = 51) and 344 m (n = 18). The evaluated distances were then divided into two; as a result, the radius of a circular territory of a single species was obtained. For the Syrian Woodpecker this radius was 113 m and for the Middle Spotted Woodpecker 172 m. Nest tree was treated as a centroid buffer and accepted for the particular single species radius, the circular buffer was delineated. This plot was determined as the range of the potential single bird pair territory area and then considered the 'territory' area. The area which was outside the determined polygon layer was considered as a space not inhabited by a particular woodpecker species and was named as 'outside territory' area. Due to the high mountain terrain, it was not possible to take measurements for all random selected points. Finally, in the field works we described 30 and 16 full tree point sets (including 'nest', 'territory' and 'outside territory' tree stands), respectively for the Syrian Woodpecker and the Middle Spotted Woodpecker.
2.5
Data handling and statistical evaluation
We compared the two measurements DBH and health condition between four groups of trees: nest trees, trees in the vicinity of the nest tree, territory trees and trees located outside the territories. We compared also the seven measurements for the 'nest', territory' and 'outside territory' tree stand plots using non-parametric data we used the Kruskal-Wallis test with post-hoc Dunn test. For comparison between Syrian Woodpecker and Middle Spotted Woodpecker data we used the Mann-Whitney U test. For qualitative variables, we also used frequency tests appropriate to the sample size. For this purpose, the Statistica 13.3 PL software was applied.
To evaluate nesting preferences of woodpeckers, we used the selection index (Manly et al., 1993).
This evaluation was done for nest trees in relations to all trees noted in nest tree stands – it was treated as a nest tree stand selection index (NTS; Table 1). Next selection index was performed for all trees noted in nest tree stands (NTS) which were referenced to trees found in territory tree stands (TTS; Table 1). This evaluation allowed us for an assessment of nesting preferences of the two woodpecker species. The last selection index was done for trees noted in territory tree stands (TTS) in regarding to all trees recorded in random selected tree plots (cumulatively inside and outside woodpecker territories) which was considered as territory preferences (TTS; Table 1). For each analyzed tree species, we calculated the selection index with a 95 % confidence interval (CI) based on Bonferroni's inequality (Manly et al., 1993). For each analyzed tree species selection index we calculated a 95 % confidence interval (CI) based on Bonferroni's inequality (Manly et al., 1993). If the confidence interval evaluated for a particular tree species was greater than 1, this meant that the tree species was preferred by woodpeckers. When it was less than 1, it meant that woodpeckers avoided such tree species. The confidence intervals of the individual selection indices containing a value of 1 meant that the woodpeckers did not have a preference for this tree species. The negative lower limit of the confidence intervals was changed to 0.00 because negative values of confidence intervals are not possible (Manly et al., 1993). The mentioned evaluation was done for nest trees in relation to all trees noted in nest tree stands – it was treated as nest tree selection index (NT; Table 1). The next selection index was performed for all trees observed in the nest tree stands (NTS) that were referenced to trees found in territory tree stands (Table 1). This evaluation allowed for an assessment of nesting preferences. The last selection index was performed for trees noted in territory tree stands in regard to trees recorded in random selected plots in subplot areas (cumulatively inside and outside woodpecker territories) which was considered as territory tree stand preferences (TTS, Table 1).
We applied linear discriminant analysis (LDA) to investigate the differences between six tree stand groups designated in the studies ('nest', 'territory' and 'outside territory' tree stands, respectively for the Syrian Woodpecker and the Middle Spotted Woodpecker). To measure pair-wise correlation between studied parameters we used the Spearaman's rank correlation (Appendix Table S3). Then to eliminate variable multicollinearity we excluded the variable 'number of trees' (with rs > 0.6) from the analysis (Appendix Table S3). Finally, five variables were included in the LDA: number of tree species, average health condition, average DBH, cumulative basal area of tree trunks, and percentage tree crown cover. In the LDA procedure for the studied variables the Wilks' lambda test and the squares of Mahalanobis distances and coefficients of standardised canonical variables, were performed. For this purpose, the R program (R Core Team, 2019) with the following packages: 'vegan' (Oksanen et al., 2008), MASS (Venables and Ripley, 2002), and 'car' (Fox and Weisberg, 2019) were applied. For graphical visualisation the libraries 'plyr' (Wickham, 2011) and 'ggplot2' (Wickham, 2016) were also used. All statistical differences were assumed at the level of p < 0.05.
3.
Results
3.1
Tree species selection
The Syrian Woodpecker was observed only in subplot W1 and the Middle Spotted Woodpecker in subplots W2–W4 (Fig. 1). The Syrian Woodpecker nested mainly in Mount Atlas Mastic, less frequently in Ash and only exceptionally in Wild Pear trees (Table 1). These three tree species had the same health condition (for all tree species Median = 2, Kruskal Wallis test H = 2.10, df = 2, p = 0.350; Appendix Table S2). The dimension of the mastic tree trunk (Median = 35.0 cm) was the largest and significantly larger than the Pear trunks (Median = 21.0 cm, Kruskal Wallis test H = 6.51, df = 2, p = 0.039, Dunn post-hoc test p = 0.033; Appendix Table S1). The Middle Spotted Woodpecker excavated nests only in Oak (Quercus brantii var. persica), which was the main tree species in the forests stands used by this woodpecker species (Table 1).
The Syrian Woodpecker preferred the Mount Atlas Mastic which was the dominant tree species in nesting tree stands of this species (Table 1). This tree species had a similar health condition as other tree species, but one of the largest tree trunk dimensions (Median = 33.0 cm; Appendix Tables S1 and S2). In such tree stands, Pears and Ashes, like the other four tree species, were found less frequently and were not preferred by this woodpecker species. Despite the fact that the Mount Atlas Mastic, Pears and Ashes also dominated in Syrian Woodpecker territory tree stands, this woodpecker species did not prefer them, as their share in forest habitats was similar (Table 1). Due to the clear dominance of Oaks in nest tree stands, and in the territory tree stands of the Middle Spotted Woodpecker, and generally in forest habitats located in these subplots, this woodpecker species did not show clear preference for this tree species (Table 1; Appendix Tables S1 and S2).
3.2
Nest tree selection and cavity placement
Syrian and Middle Spotted Woodpeckers nested in trees with similar trunk dimensions (DBH respectively means 37.8 cm and 38.8 cm; Table 2). The nest trees of both species had, on average, 10 cm larger trunks (DBH) compared to trees observed in the vicinity of the nests. These differences in trunk dimensions were statistically significant (Table 2). Nest trees also had significantly larger trunks compared to trees found in the territories, as well as trees noted outside the territories of both species (Table 2). The nest trees of both species also had a similar health status (Median = 2 for both species; Table 2). However, the nest trees of both Syrian and Middle Spotted Woodpeckers were in a poor health condition compared to trees located in the vicinity of nest trees, inside, and outside the woodpecker territories (Table 2). There were no statistical differences for this variable between the other categories of trees (Table 2).
Table
2.
Characteristic of the nest trees used by woodpeckers in relation to trees located in the nest tree vicinity, inside woodpecker territory and outside woodpecker territory sites.
Variable/Species
Nest trees
Trees in the vicinity of nest tree
Trees in territory
Trees outside the territory
Kruskal-Wallis test (df = 3)
Tree DBH (cm)
Syrian Woodpecker
37.8 ± 15.5a 32.5 (18.0–68.0) n = 30
27.6 ± 10.6b 25.0 (16.0–55.0) n = 73
28.3 ± 11.7c 25.0 (16.0–65.0) n = 71
29.3 ± 10.6d 25.0 (16.0–96.0) n = 74
H = 13.9 p < 0.001 ab p < 0.001 ac p < 0.001 ad p < 0.001
Middle Spotted Woodpecker
38.8 ± 13.1a 40.0 (21.0–68.0) n = 16
27.0 ± 8.9b 25.0 (16.0–62.0) n = 102
24.7 ± 7.7c 22.0 (16.0–48.0) n = 113
24.4 ± 8.9d 20.0 (16.0–53.0) n = 92
H = 26.6 p < 0.001 ab p = 0.006 ac p < 0.001 ad p < 0.001 bd p = 0.031
Mann-Whitney U test
Z = 0.58 P = 0.564
Z = 0.25 P = 0.800
Z = −1.59 P = 0.110
Z = −2.75 P = 0.006
Tree conditio
Syrian Woodpecker
2.1 ± 0.6a 2.0 (1.0–3.0) n = 30
1.0 ± 0.2b 1.0 (1.0–2.0) n = 73
1.2 ± 0.5c 1.0 (1.0–4.0) n = 71
1.4 ± 1.0d 1.0 (1.0–5.0) n = 74
H = 92.5 p < 0.001 ab p < 0.001 ac p < 0.001 ad p < 0.001
Middle Spotted Woodpecker
2.6 ± 0.8a 2.0 (2.0–4.0) n = 16
1.2 ± 0.8b 1.0 (1.0–6.0) n = 102
1.4 ± 1.1c 1.0 (1.0–6.0) n = 113
1.1 ± 0.5d 1.0 (1.0–4.0) n = 92
H = 105.2 p < 0.001 ab p < 0.001 ac p < 0.001 ad p < 0.001
Mann-Whitney U test
Z = 1.92 P = 0.054
Z = 0.46 P = 0.648
Z = 1.01 P = 0.308
Z = −2.67 P = 0.007
Mean values ± standard deviation, median (Me), minimum, and maximum values (in brackets) of the measured parameters are presented.
The Syrian Woodpecker excavated cavities mainly in tree trunks (73%, n = 30), while the Middle Spotted Woodpecker located its nests generally in tree branches (62%, n = 16; Fig. 2). These differences were statistically significant (Yates' corrected Chi-square test = 4.22, df = 1, p = 0.040). The share of trees reused for nesting by woodpeckers (already having other old cavities) was similar in both species (V-square test = 0.35, df = 1, p = 0.555) and accounted for approximately 47% (n = 30) for the Syrian Woodpecker and 38% (n = 16) for the Middle Spotted Woodpecker. The trees reused by Syrian Woodpeckers for nesting had larger trunks compared to the tree trunks that were only used currently for nesting (included only one cavity) by woodpeckers (respectively Median = 36.5 cm, n = 14 and Median = 29.8 cm, n = 16, Mann-Whitney U test, Z = 2.08, p = 0.038). Similar dependences, but not statistically significant (Mann-Whitney U test, Z = 1.14, p = 0.255), are also evident for the Middle Spotted Woodpecker. Tree trunks containing several old cavities that were reused by this species were larger (Median = 41.6 cm, n = 6) compared to trees that included only the one cavity that was used for the breeding by a woodpecker pair in the current season (Median = 33.0 cm, n = 10).
Figure
2.
Share of cavities located in trunks and branches of the nest trees used by woodpeckers. Denotations: grey – cavities located in branches; white – cavities located in trunks.
Some parameters of the Syrian Woodpecker and Middle Spotted Woodpecker nest tree stands were significantly different from the tree stands recorded inside and outside the breeding pair territories (Table 3). In the Syrian Woodpecker nest tree stands, significantly higher tree diversity was found than in tree stands recorded outside of the birds' territories (Table 3). The nest tree stands also had the highest tree density, but in relation to the other types of tree stand considered, there were no statistical differences. The Syrian Woodpecker nest and territory tree stands also had a better tree health condition compared to the tree stands recorded outside the woodpecker territories. They also had a larger basal area and a larger share of the tree crown area compared to the tree stands recorded inside and outside the Syrian Woodpecker territories (Table 3). A significantly larger tree crown cover was also found in the territories than outside the woodpecker territories. The diameter of the tree trunks was also the largest in the nest stands, but was similar to the trees found inside the territories and outside the Syrian Woodpecker territories (Table 3).
Table
3.
The characteristics of the tree stands used by woodpeckers for nesting in relation to territory tree stands and outside territory tree stands. Statistical differences between Syrian Woodpecker and Middle Spotted Woodpecker are bolded.
Tree stands
Syrian Woodpecker (n = 30) mean ± SD Median (min.–max.)
Middle Spotted Woodpecker (n = 16) mean ± SD Median (min.–max.)
Mann-Whitney U test
Nest tree stands
Number of trees
4.4 ± 2.3 4.0 (1.0–9.0)
7.6 ± 3.6 7.5 (2.0–14.0)
Z = 3.07 P = 0.002
Number of tree species
2.4 ± 1.0a 2.0 (1.0–4.0)
1.1 ± 0.2 2.0 (1.0–4.0)
Z = −4.22 P < 0.001
Tree condition
1.3 ± 0.2b 1.2 (1.0–3.0)
1.4 ± 0.4a 1.2 (1.0–2.6)
Z = 0.37 P = 0.712
Tree DBH (cm)
28.7 ± 11.8 24.0 (17.0–60.0)
28.5 ± 5.7 27.6 (18.6–36.9)
Z = 0.88 P = 0.375
Basal area (m2)
0.30 ± 0.10de 0.27 (0.10–0.56)
0.54 ± 0.26b 0.54 (0.09–0.97)
Z = 3.40 P < 0.001
Tree crown cover
26.7 ± 12.8 fg 25.1 (0.8–54.8)
53.6 ± 19.0c 58.9 (10.6–80.6)
Z = 4.09 P < 0.001
Territory tree stands
Number of trees
3.4 ± 2.3 3.0 (1.0–11.0)
7.5 ± 3.1 6.0 (3.0–13.0)
Z = 4.06 P < 0.001
Number of tree species
1.9 ± 0.9 2.0 (1.0–4.0)
1.1 ± 0.3 1.0 (1.0–4.2)
Z = −2.80 P = 0.005
Tree condition
1.0 ± 0.2c 1.0 (1.0–2.0)
1.4 ± 0.9 1.2 (1.0–4.2)
Z = 2.25 P = 0.024
Tree DBH (cm)
23.2 ± 10.7 21.7 (11.0–50.0)
32.8 ± 33.0 24.5 (18.0–155.4)
Z = 1.30 P = 0.193
Basal area (m2)
0.19 ± 0.19d 0.13 (0.10–0.80)
0.36 ± 0.20 0.37 (0.04–0.76)
Z = 2.87 P = 0.004
Tree crown cover
16.0 ± 11.0fh 15.4 (0.9–44.4)
44.9 ± 14.3 45.7 (17.0–73.4)
Z = 4.90 P < 0.001
Outside territory tree stands
Number of trees
3.1 ± 2.0 3.0 (1.0–10.0)
6.9 ± 2.6 7.5 (3.0–12.0)
Z = 4.24 P < 0.001
Number of tree species
1.5 ± 0.9a 1.0 (1.0–5.0)
1.1 ± 0.2 1.0 (1.0–2.0)
Z = −1.71 P = 0.087
Tree condition
1.6 ± 0.9bc 1.0 (1.0–5.0)
1.1 ± 0.3a 1.0 (1.0–1.8)
Z = −1.61 P = 0.106
Tree DBH (cm)
26.1 ± 15.1 22.7 (10.0–85.0)
37.2 ± 37.4 24.0 (13.8–139.5)
Z = 0.84 P = 0.400
Basal area (m2)
0.21 ± 0.23e 0.13 (0.01–0.91)
0.31 ± 0.24b 0.29 (0.03–0.95)
Z = 1.62 P = 0.104
Tree crown cover
9.0 ± 7.1gh 6.0 (0.7–24.4)
44.8 ± 10.5c 39.7 (26.8–60.6)
Z = 5.32 P < 0.001
Kruskal-Wallis test (df = 2)
Number of trees
H = 5.41; P = 0.067
H = 0.37; P = 0.833
–
Number of species
H = 13.06; P = 0.002 a p = 0.002
H = 0.53; P = 0.766
–
Tree condition
H = 19.01; P = 0.001 b p = 0.002; c p = 0.002
H = 8.28; P = 0.016 a p = 0.017
–
Tree DBH
H = 3.77; P = 0.152
H = 2.78; P = 0.249
–
Basal area (m2)
H = 14.74; P < 0.001 d p = 0.001; e p = 0.005
H = 8.14; P = 0.017 b p = 0.016
–
Tree crown cover
H = 29.72; P < 0.001 f p = 0.008; g p < 0.001; h p = 0.046
The nest, territory and outside territory tree stands of the Middle Spotted Woodpecker had a similar number of trees and tree species (Table 3). Nest tree stands also had a similar tree health condition in comparison to trees recorded in the territories, but were significantly more deteriorated than those recorded outside the territories of this woodpecker species. The nest tree stands also contained trees with the smallest dimensions of the tree trunks, but these differences were not statistically significant compared to trees noted in territory and outside the territory tree stands (Table 3). The nest tree stands of the Middle Spotted Woodpecker also had a larger basal area and share of the tree crown area compared to the tree stands recorded inside and outside the bird territories (Table 3). However, statistically significant differences were found only between the nest and those outside territory tree stands of the Middle Spotted Woodpecker breeding pairs (Table 3).
We found clear differences between the forest stands inhabited by Syrian and Middle Spotted Woodpeckers (Table 3). Although fewer trees were found in the nesting stands of the Syrian Woodpecker, they were characterised by a greater number of tree species. The nesting stands of the first species also had a significantly smaller basal area and the share of tree crown area compared to the tree stands occupied by the Middle Spotted Woodpecker. When evaluating the four parameters mentioned above, the same dependencies can also be seen in the comparison of tree stands recorded in the territories and outside the territories of both studied species (Table 3). The nest stands of the Syrian and Middle Spotted Woodpecker had a similar tree health condition. Only the Middle Spotted Woodpecker territory tree stands had significantly worse tree health conditions compared to the Syrian Woodpecker territory tree stands (Table 3). The diameter of the tree trunks in the nesting stands of the Syrian and Middle Spotted Woodpecker was also similar. There were no statistical differences in the dimensions of the tree trunks recorded inside and outside the territories of both these woodpecker species (Table 3).
The LDA also showed different preferences in the forest habitats inhabited by the Syrian and Middle Spotted Woodpeckers (Wilks' Lambda test 0.179, F25.477 = 11.24, p < 0.001). There were clear differences between the nest tree stands, the tree stands and also outside territory tree stands outside the territory of the two woodpecker species (Fig. 3, Table 4). The four most important factors that separated the types of tree stands were: tree number (1), tree condition (2), basal area (3) share of tree crown cover area (4) (Table 5). The first canonical variable explains 86 % of the variability and indicates that the share of the tree crown area is the most important factor. The second canonical variable, that explains only 9 % of the variability, indicates that the number of tree species in the tree stand may be a factor which can help distinguish the analyzed groups of tree stands (Fig. 3, Table 6).
Figure
3.
Relationships between the considered categories of tree stands presenting the occurrence of the Syrian Woodpecker (SW) and the Middle Spotted Woodpecker (MSW) on the basis of the two first LDA canonical variables.
Table
4.
Matrix of tree stand variants tested in LDA presenting the squares of Mahalanobis distances, F statistic values (df = 5, 128) and the probability level.
Variant of tree stand
MswN
MswT
MswO
SwN
SwT
SwO
MswN
0.00
1.61 F = 2.50 P = 0.034
3.39 F = 5.26 P < 0.001
13.85 F = 28.04 P < 0.001
19.51 F = 39.04 P < 0.001
19.52 F = 39.51 P < 0.001
MswT
0.00
0.60 F =? P = 0.459
7.35 F = 14.88 P < 0.001
11.28 F = 22.83 P < 0.001
11.29 F = 22.85 P < 0.001
MswO
0.00
5.86 F = 11.85 P < 0.001
8.47 F = 17.15 P < 0.001
9.37 F = 18.96 P < 0.001
SwN
0.00
1.45 F = 4.21 P = 0.001
2.85 F = 8.28 P < 0.001
SwT
0.00
1.45 F = 4.23 P = 0.001
SwO
0.00
Denotations: MswN – Middle Spotted Woodpecker nest tree stands; MswT – Middle Spotted Woodpecker territory tree stands; MswO – Middle Spotted Woodpecker outside territory tree stands; SwN – Syrian Woodpecker nest tree stands; SwT – Syrian Woodpecker territory tree stands; SwO – Syrian Woodpecker outside territory tree stands.
In the case of both woodpecker species studied, the highest frequency of trees with old woodpecker nests was found in nest tree stands (Fig. 4A and B). In the case of the Syrian Woodpecker, the frequency of tree stands with trees that included old cavities was 47% (n = 30) and in the case of the Middle Spotted Woodpecker it was 38% (n = 16). However, there were no statistical differences between these compared tree stands (V-square test = 0.35, df = 1, p = 0.555). Compared to the Syrian Woodpecker nest tree stands, trees with old cavities were found twice as often in territory tree stands in the territories of this woodpecker species (23%, n = 30; Fig. 4A), but these differences were also not statistically significant (V-square test = 3.53, df = 1, p = 0.060). The tree stands located outside the breeding pair territories were characterised by the lowest frequency of trees with cavities (13%, n = 30). These differences were not statistically significant in comparison to tree stands located within woodpecker territories (V-square test = 0.99, df = 1, p = 0.321), but were significantly different in relation to nest tree stands of this bird species (V-square test = 7.80, df = 1, p = 0.005). Identical relationships were noted for the Middle Spotted Woodpecker. The highest frequency of tree stands with trees that contained old cavities was recorded in the nest tree stands and was not statistically different in comparison to territory tree stands (19%, n = 16, Fisher exact test p = 0.433). Tree stands with old cavities were also the least frequently recorded in outside territory tree stands of this species (6%, n = 16; Fig. 4B). This frequency was not statistically lower compared to nest tree stands (Fisher's exact test p = 0.083), as well as those in bird territories (Fisher's exact test p = 0.600). There were also no statistical differences in the frequency of tree stands that contained old cavities between the Syrian and Middle Spotted Woodpeckers when analysing tree stands recorded in territories and outside territories of both these bird species (respectively Yates' corrected Chi-square test = 0.00, df = 1, p = 0.987 and Yates' corrected Chi-square test = 0.06, df = 1, p = 0.812; Fig. 4A and B).
Figure
4.
The share of tree stands included trees with old woodpecker cavities noted in the Syrian Woodpecker (A, n = 30) and the Middle Spotted Woodpecker (B, n = 16) forest habitats. Denotations: grey – tree stands with old cavities; white – tree stands without old cavities.
Our results show that Syrian and Middle Spotted Woodpeckers selected quite different forest habitats in the mountain landscape of Southwest Iran. The Middle Spotted Woodpecker inhabited exclusively Oak (Quercus spp.) forest stands, and such a clear habitat preference for the same forest type was found for this species also in several regions in Europe (Pettersson, 1985; Pasinelli, 2000; Robles and Ciudad, 2012; Walczak et al., 2013; Wiesner and Klaus, 2018; Michalczuk and Michalczuk, 2023). The Syrian Woodpecker inhabited heterogenic forest, which contained many tree species, included the preferred Mount Atlas Mastic. In Europe, the Syrian Woodpecker also inhabits species-diverse tree stands, and generally they are non-forest tree stands which consist mainly of deciduous tree species (Szlivka, 1957; Ruge, 1969; Winkler, 1972; Cramp, 1985; Michalczuk and Michalczuk, 2016b, 2016d, 2020a; Figarski and Kajtoch, 2018). Use of such different tree habitats by both studied species is probably the result of the selection of tree stands that include adequate food resources. In the case of the Middle Spotted Woodpecker, these are oak stands that can be rich in invertebrate assemblages (e.g., Fager, 1968; Bouget et al., 2012) which are the crucial diet of these woodpeckers (Cramp, 1985). The Syrian Woodpecker is an ecologically plastic species and can feed on a lot of invertebrates, and also seeds or fruits of various plant species (Szlivka, 1962; Winkler, 1972; Cramp, 1985; Michalczuk and Michalczuk, 2017). Perhaps for this reason, this species preferred forest stands with Mount Atlas Mastic trees, because the seeds of this tree species may also be included in the diet of this woodpecker species, along with other plant seeds (Cramp, 1985). Using a variety of food resources will probably allow the Syrian Woodpecker to inhabit various tree stands in comparison to the more specialized species, Middle Spotted Woodpecker, which feeds nestlings only with invertebrates (Cramp, 1985). The use by the Syrian Woodpecker of such habitats, indicates that this species in the natural mountain forests of Southwest Asia has acquired adaptations that allow it to use food of plant origin (Winkler, 1972; Cramp, 1985). It can be assumed that this adaptation allowed this species to colonise synanthropic non-forest tree stands such as orchards, tree alleys etc., which are avoided by other woodpecker species in Asia and Europe (Cramp, 1985; Winkler et al., 1995; Winkler and Christie, 2002).
In comparison to the omnivorous Syrian Woodpecker, the Middle Spotted Woodpecker may require more significant effort to find food in forest habitats. Probably for this reason, the territories of the Middle Spotted Woodpecker in the research area were located in more dense forest stands (with a greater cover of tree crowns) compared to the habitats occupied by the Syrian Woodpecker. In the Middle Spotted Woodpecker territories, a greater number of trees and, at the same time, a larger basal tree trunk area was recorded. The values of these analyzed parameters were approximately twice as high in the Middle Spotted Woodpecker territories compared to the territories occupied by the Syrian Woodpecker. It can be assumed that forest habitats with such tree stands may provide birds a greater resource of invertebrates, which are the basic diet of Middle Spotted Woodpeckers (e.g., Cramp, 1985). Our studies have also shown that the presence of trees in a poor health condition may be less important for the presence of both species in studied habitats. Although the presence of such trees may also increase the availability of woodpecker's food in the form of many invertebrates, e.g., saproxylic beetles (Ranius and Jansson, 2000; Laaksonen et al., 2020), both Middle Spotted Woodpecker and Syrian Woodpecker are species that avoid digging deep into the tree and obtain food by searching mainly the surface of the tree bark (Winkler, 1973; Stański et al., 2021). Due to the fact that beetle larvae are not the basic food of Middle Spotted and Syrian Woodpeckers (Cramp, 1985; Michalczuk and Michalczuk, 2017), this is probably why habitat preferences for trees with poor health condition were not recorded in both studied species.
However, health condition and large dimension of trees were more important to both species when selecting nesting sites. Selection of such trees for nesting by the studied woodpeckers may be due to the fact that these trees may include appropriate places for cavity locations. Many studies have shown that woodpeckers prefer larger and often weakened trees for nesting, because such trees provide a suitable substrate for cavity excavating (e.g., Kosiński and Kempa, 2007; Michalczuk and Michalczuk, 2020a). Our research in Iran for the Middle Spotted Woodpecker showed, these were mature oaks, which are a suitable tree species for nesting by this species of woodpecker, which was also confirmed in many other regions (Pasinelli, 2000; Kosiński et al., 2006; Wiesner and Klaus, 2018). However, the diameters of the trunks of nesting trees in the study area (about 40 cm) were smaller compared to trees used for nesting by Middle Spotted Woodpeckers in other regions, e.g., Europe, where they were, on average, in excess of 50 cm, and even 60 cm (Kosiński et al., 2006; Kosiński and Kempa, 2007; Pasinelli, 2007). They were about 10–20 cm larger compared to trees used for nesting by this species in Iran (Mohamadian et al., 2019). Only occasionally the Middle Spotted Woodpecker used other tree species for nesting e.g., Ash, and these used trees were also impressive in size, with average trunk diameters of 70 cm (Kosiński et al., 2006). Because mastics were the largest trees in the whole assemblage of trees which consisted of mixed tree stands occupied by Syrian Woodpecker, such trees probably provided suitable nesting sites for this species as well. Similar relationships can also be confirmed in another region of Iran (Aghanajafizadeh et al., 2011). Such relationships were also found in the agricultural landscape of Southeast Poland, where birds preferred trees that had larger trunk dimensions compared to trees available in the environment (Michalczuk and Michalczuk, 2016e, 2020a). The average diameter of nest tree trunks in Southeast Poland (average 45–47 cm) was slightly larger than in Iran (about 40 cm, e.g., Mohamadian et al., 2019a), which may result from different features of the tree stands, which are probably more robust in Central Europe in comparison to the mountain forest habitats of Southwest Asia (see Aghanajafizadeh et al., 2011; Michalczuk and Michalczuk, 2016e, 2020a, 2020b; Mohamadian et al., 2019a; Michalczuk, 2020).
Woodpecker nest trees were often in a more deteriorated health condition compared to trees present in the habitats. Trees selected by woodpeckers for nesting often have broken branches or dead tree fragments, which are suitable substrate to cavity excavating (Kosiński and Kempa, 2007; Michalczuk and Michalczuk, 2020a). In the study area, the health condition of Syrian Woodpecker nesting trees was also poor, as with nesting trees of this species noted in the agricultural landscape of southeastern Poland (Michalczuk and Michalczuk, 2016e, 2020a, 2020b; Michalczuk, 2020). As we found and other studies also found (e.g., Kosiński and Kempa, 2007), the presence of such trees in habitats is an important factor determining the occurrence of the Middle Spotted Woodpecker in forests. It is a crucial factor confirmed by the re-nesting of woodpeckers in tree stands where trees with old cavities were often present. The frequent presence of old cavities also in the nesting trees indicates that such habitats are important for the occurrence of the studied species and indicate that woodpeckers can use them for several seasons. As our research has shown, the diameter of trees repeatedly used by woodpeckers for nesting was much larger compared to trees that include only single cavities used in the current breeding season. The re-nesting of woodpeckers in such trees indicates that an important factor positively influencing the stability of woodpecker breeding sites in natural forests of the Iranian mountains is the presence of trees with large trunk dimensions.
Reuse of trees with old cavities suggests that the woodpeckers that inhabit the mountain forests of the study region are not under strong predation pressure (Mohamadian et al., 2019b). In certain regions, e.g., in Central Europe, a number of cavity nesters' broods can be destroyed by Martens Mustelidae or Rodents Rodentia (Mazgajski, 2002; Paclik et al., 2009). But generally, the nesting success of cavity nesters is high and often reaches up to 60% and over 80% (e.g., Kosiński et al., 2006) and only occasionally is lower at the level of 50–60% (Michalczuk and Michalczuk, 2016a). Perhaps for this reason, in the Southwest Iran region the Syrian Woodpecker can excavate cavities lower above ground level and more often in tree trunks, compared to the population of this species inhabiting Europe where birds build nests also in trunks, but often in branches too (Szlivka, 1957, 1962; Ruge, 1969; Michalczuk and Michalczuk, 2020a). Specifically, the average height of Syrian Woodpecker nest locations in Europe ranges from two up to 4 m above the ground (Szlivka, 1957, 1962; Ruge, 1969; Michalczuk and Michalczuk, 2016e), while in Southwest Asia it is about 2 m above the ground level (Al-Safadi, 2004; Ar et al., 2004; Mohamadian et al., 2019a). The presence of Middle Spotted Woodpecker nests at a level of about 4 m above ground level (Mohamadian et al., 2019a) compared to the location of nests in Europe which exceed on average about 10–12 m above ground level (Kosiński et al., 2006; Kosiński and Kempa, 2007) suggests that these differences may also result from lower tree stands present in the mountains of Iran (authors' own observations).
5.
Conclusions
We conclude that in the mountain area of Southwest Iran, for the protection of the Syrian Woodpecker habitat, it is important to preserve heterogenic forest stands containing the preferred tree species, such as Mount Atlas Mastic trees. It can be assumed that adaptation of Syrian Woodpecker to use such habitat including tree species that produce fruits and seeds, allowed this species to colonise in Asia and Europe non-forest tree stands such as orchards, gardens or tree alleys. The protection of the habitats of Middle Spotted Woodpecker should focus on oak forest stands, which consist of more trees, as well as twice the area of tree crowns in habitats compared to sites inhabited by the Syrian Woodpecker. To preserve the habitats of both woodpecker species, it is also important to conserve trees with larger trunk dimensions and poor health conditions in the forests. The presence of such trees in forests is crucial to ensure the stability of nesting sites for both species. Maintaining the habitats of Syrian and Middle Spotted Woodpeckers can be achieved by preserving natural forests in the Iranian mountains.
Ethics statement
The research was carried out in accordance with accepted scientific standards and in accordance with the law at the place of field work.
CRediT authorship contribution statement
Arya Shafaeipour: Writing – review & editing, Writing – original draft, Resources, Investigation, Data curation, Conceptualization. Jerzy Michalczuk: Writing – review & editing, Writing – original draft, Software, Formal analysis, Conceptualization. Behzad Fathinia: Writing – review & editing, Writing – original draft, Resources, Investigation, Data curation, Conceptualization.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper..
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Table
1.
Tree species composition of tree stands in natural forest of SW Iran.
Tree species
Nest trees–NT
Trees in the vicinity of nest trees–TV
Trees in nest tree stands–NTS (NT+TV)
Trees in territory tree stands–TTS
Trees outside the territory tree stands–OTT
Tree stands total–TPT (TTS+OTT)
Syrian Woodpecker
Acer (Acer monspessulanum)
–
8.2 (6)
5.8 (6)^
4.2 (3)^
5.4 (4)
4.8 (7)
Ash (Fraxinus angustifolia)
30.0 (9)*
9.6 (7)
12.6 (13)^
28.2 (20)^
32.4 (24)
30.3 (44)
Honeysuckle (Lonicera nummularifolia)
–
8.2 (6)
5.8 (6)^
4.2 (3)^
2.7 (2)
3.4 (5)
Dotted Hawthorn (Crataegus puntica)
–
4.1 (3)
2.9 (3)^
8.5 (6)^
1.4 (1)
4.8 (7)
Mount Atlas Mastic (Pistacia atlantica)
60.0 (18)*
38.4 (28)
44.7 (46)*
32.4 (23)^
17.6 (13)
24.8 (36)
Oak (Quercus brantii var. persica)
–
2.7 (2)
1.9 (2)^
4.2 (3)^
6.8 (5)
5.5 (8)
Wild Pear (Pyrus glabra)
10.0 (3)^
28.8 (21)
23.3 (24)^
18.3 (13)^
31.1 (23)
24.8 (36)
Willow (Salix excelsa)
–
–
–
–
2.7 (2)
1.4 (2)
All trees
30
73
103
71
74
145
Middle Spotted Woodpecker
Ash (Fraxinus angustifolia)
–
–
–
0.8 (1)
–
0.4 (1)
Mount Atlas Mastic (Pistacia atlantica)
–
0.9 (1)
0.8 (1)^
0.8 (1)^
0.9 (1)
0.9 (2)
Oak (Quercus brantii var. persica)
100.0 (16)^
99.1 (106)
99.2 (122)^
98.6 (118)^
99.1 (106)
98.7 (224)
All trees
16
107
123
120
107
227
Percentage share and number of cases (in brackets) of specified tree stands described for studied woodpecker species. *–tree species preferred by woodpeckers; ^–tree species not preferred by woodpeckers; studies did not identify tree species avoided by woodpeckers (evaluation done according to Manly selection index – for details see Materials and Method).
Table
2.
Characteristic of the nest trees used by woodpeckers in relation to trees located in the nest tree vicinity, inside woodpecker territory and outside woodpecker territory sites.
Variable/Species
Nest trees
Trees in the vicinity of nest tree
Trees in territory
Trees outside the territory
Kruskal-Wallis test (df = 3)
Tree DBH (cm)
Syrian Woodpecker
37.8 ± 15.5a 32.5 (18.0–68.0) n = 30
27.6 ± 10.6b 25.0 (16.0–55.0) n = 73
28.3 ± 11.7c 25.0 (16.0–65.0) n = 71
29.3 ± 10.6d 25.0 (16.0–96.0) n = 74
H = 13.9 p < 0.001 ab p < 0.001 ac p < 0.001 ad p < 0.001
Middle Spotted Woodpecker
38.8 ± 13.1a 40.0 (21.0–68.0) n = 16
27.0 ± 8.9b 25.0 (16.0–62.0) n = 102
24.7 ± 7.7c 22.0 (16.0–48.0) n = 113
24.4 ± 8.9d 20.0 (16.0–53.0) n = 92
H = 26.6 p < 0.001 ab p = 0.006 ac p < 0.001 ad p < 0.001 bd p = 0.031
Mann-Whitney U test
Z = 0.58 P = 0.564
Z = 0.25 P = 0.800
Z = −1.59 P = 0.110
Z = −2.75 P = 0.006
Tree conditio
Syrian Woodpecker
2.1 ± 0.6a 2.0 (1.0–3.0) n = 30
1.0 ± 0.2b 1.0 (1.0–2.0) n = 73
1.2 ± 0.5c 1.0 (1.0–4.0) n = 71
1.4 ± 1.0d 1.0 (1.0–5.0) n = 74
H = 92.5 p < 0.001 ab p < 0.001 ac p < 0.001 ad p < 0.001
Middle Spotted Woodpecker
2.6 ± 0.8a 2.0 (2.0–4.0) n = 16
1.2 ± 0.8b 1.0 (1.0–6.0) n = 102
1.4 ± 1.1c 1.0 (1.0–6.0) n = 113
1.1 ± 0.5d 1.0 (1.0–4.0) n = 92
H = 105.2 p < 0.001 ab p < 0.001 ac p < 0.001 ad p < 0.001
Mann-Whitney U test
Z = 1.92 P = 0.054
Z = 0.46 P = 0.648
Z = 1.01 P = 0.308
Z = −2.67 P = 0.007
Mean values ± standard deviation, median (Me), minimum, and maximum values (in brackets) of the measured parameters are presented.
Table
3.
The characteristics of the tree stands used by woodpeckers for nesting in relation to territory tree stands and outside territory tree stands. Statistical differences between Syrian Woodpecker and Middle Spotted Woodpecker are bolded.
Tree stands
Syrian Woodpecker (n = 30) mean ± SD Median (min.–max.)
Middle Spotted Woodpecker (n = 16) mean ± SD Median (min.–max.)
Mann-Whitney U test
Nest tree stands
Number of trees
4.4 ± 2.3 4.0 (1.0–9.0)
7.6 ± 3.6 7.5 (2.0–14.0)
Z = 3.07 P = 0.002
Number of tree species
2.4 ± 1.0a 2.0 (1.0–4.0)
1.1 ± 0.2 2.0 (1.0–4.0)
Z = −4.22 P < 0.001
Tree condition
1.3 ± 0.2b 1.2 (1.0–3.0)
1.4 ± 0.4a 1.2 (1.0–2.6)
Z = 0.37 P = 0.712
Tree DBH (cm)
28.7 ± 11.8 24.0 (17.0–60.0)
28.5 ± 5.7 27.6 (18.6–36.9)
Z = 0.88 P = 0.375
Basal area (m2)
0.30 ± 0.10de 0.27 (0.10–0.56)
0.54 ± 0.26b 0.54 (0.09–0.97)
Z = 3.40 P < 0.001
Tree crown cover
26.7 ± 12.8 fg 25.1 (0.8–54.8)
53.6 ± 19.0c 58.9 (10.6–80.6)
Z = 4.09 P < 0.001
Territory tree stands
Number of trees
3.4 ± 2.3 3.0 (1.0–11.0)
7.5 ± 3.1 6.0 (3.0–13.0)
Z = 4.06 P < 0.001
Number of tree species
1.9 ± 0.9 2.0 (1.0–4.0)
1.1 ± 0.3 1.0 (1.0–4.2)
Z = −2.80 P = 0.005
Tree condition
1.0 ± 0.2c 1.0 (1.0–2.0)
1.4 ± 0.9 1.2 (1.0–4.2)
Z = 2.25 P = 0.024
Tree DBH (cm)
23.2 ± 10.7 21.7 (11.0–50.0)
32.8 ± 33.0 24.5 (18.0–155.4)
Z = 1.30 P = 0.193
Basal area (m2)
0.19 ± 0.19d 0.13 (0.10–0.80)
0.36 ± 0.20 0.37 (0.04–0.76)
Z = 2.87 P = 0.004
Tree crown cover
16.0 ± 11.0fh 15.4 (0.9–44.4)
44.9 ± 14.3 45.7 (17.0–73.4)
Z = 4.90 P < 0.001
Outside territory tree stands
Number of trees
3.1 ± 2.0 3.0 (1.0–10.0)
6.9 ± 2.6 7.5 (3.0–12.0)
Z = 4.24 P < 0.001
Number of tree species
1.5 ± 0.9a 1.0 (1.0–5.0)
1.1 ± 0.2 1.0 (1.0–2.0)
Z = −1.71 P = 0.087
Tree condition
1.6 ± 0.9bc 1.0 (1.0–5.0)
1.1 ± 0.3a 1.0 (1.0–1.8)
Z = −1.61 P = 0.106
Tree DBH (cm)
26.1 ± 15.1 22.7 (10.0–85.0)
37.2 ± 37.4 24.0 (13.8–139.5)
Z = 0.84 P = 0.400
Basal area (m2)
0.21 ± 0.23e 0.13 (0.01–0.91)
0.31 ± 0.24b 0.29 (0.03–0.95)
Z = 1.62 P = 0.104
Tree crown cover
9.0 ± 7.1gh 6.0 (0.7–24.4)
44.8 ± 10.5c 39.7 (26.8–60.6)
Z = 5.32 P < 0.001
Kruskal-Wallis test (df = 2)
Number of trees
H = 5.41; P = 0.067
H = 0.37; P = 0.833
–
Number of species
H = 13.06; P = 0.002 a p = 0.002
H = 0.53; P = 0.766
–
Tree condition
H = 19.01; P = 0.001 b p = 0.002; c p = 0.002
H = 8.28; P = 0.016 a p = 0.017
–
Tree DBH
H = 3.77; P = 0.152
H = 2.78; P = 0.249
–
Basal area (m2)
H = 14.74; P < 0.001 d p = 0.001; e p = 0.005
H = 8.14; P = 0.017 b p = 0.016
–
Tree crown cover
H = 29.72; P < 0.001 f p = 0.008; g p < 0.001; h p = 0.046
Table
4.
Matrix of tree stand variants tested in LDA presenting the squares of Mahalanobis distances, F statistic values (df = 5, 128) and the probability level.
Variant of tree stand
MswN
MswT
MswO
SwN
SwT
SwO
MswN
0.00
1.61 F = 2.50 P = 0.034
3.39 F = 5.26 P < 0.001
13.85 F = 28.04 P < 0.001
19.51 F = 39.04 P < 0.001
19.52 F = 39.51 P < 0.001
MswT
0.00
0.60 F =? P = 0.459
7.35 F = 14.88 P < 0.001
11.28 F = 22.83 P < 0.001
11.29 F = 22.85 P < 0.001
MswO
0.00
5.86 F = 11.85 P < 0.001
8.47 F = 17.15 P < 0.001
9.37 F = 18.96 P < 0.001
SwN
0.00
1.45 F = 4.21 P = 0.001
2.85 F = 8.28 P < 0.001
SwT
0.00
1.45 F = 4.23 P = 0.001
SwO
0.00
Denotations: MswN – Middle Spotted Woodpecker nest tree stands; MswT – Middle Spotted Woodpecker territory tree stands; MswO – Middle Spotted Woodpecker outside territory tree stands; SwN – Syrian Woodpecker nest tree stands; SwT – Syrian Woodpecker territory tree stands; SwO – Syrian Woodpecker outside territory tree stands.
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