Comparative Ecological and Geographical Analysis of the Anvils of the Great Spotted Woodpecker Dendrocopos major (Aves: Piciformes) in the North and South of the European Part of Russia

Abstract

The Great Spotted Woodpecker (GSW), Dendrocopos major, has a huge range stretching from the Canary Islands and Northwest Africa east to Kamchatka and Sakhalin Island. The feeding behavior of the GSW is characterised by a high diversity and pronounced seasonality. Thus, in late spring and summer in the feeding repertoire of the GSW in the North and in the Central regions of the European part of Russia, there are exclusively methods of searching for and picking openly living invertebrates. The search for prey is carried out both on woody vegetation and on the ground surface. We have also repeatedly observed the hunting from perches in the manner of Flycatchers on flying dragonflies and butterflies. From late summer, GSWs begin to use chiseling tree trunks and branches in search of xylophages larvae. The GSW intensively uses anvils in winter (starting in November) and early spring. The relevance of this study is determined not only by the fragmentation and insufficient information on the GSW’s anvils, but also by the fact that there is no comparison of anvils from distant geographical regions where different subspecies of the GSW are common. For the first time in a comparative aspect, the features of the GSW’s anvils from different geographical populations are analyzed. The GSW’s use of the so-called “anvils” – the places of processing food-containing and food objects – is well known, which is reflected both in general articles on ecology and feeding behavior of this species and in some publications devoted to this particular issue (mainly fragmentary in nature). This well-known phenomenon is also reflected in monographs and faunal reports. Within the vast range of the GSW, various authors distinguish from 14 to 26 subspecies. In Russia and adjacent territories, there are 7 subspecies. In Arkhangelsk oblast (AO), the nominative subspecies D. m. major is distributed. In Stavropol oblast (SO), the subspecies D. m. tenuirostris is common, according to other sources, it is considered as D. m. pinetorum. Unlike the nominative subspecies, D. m. tenuitostris has a longer and narrower bill, well adapted for punching holes in the strong shells of stone fruits (apricot, plum), walnut, and almonds. In Ciscaucasia, there is a wide zone of intergradation of D. m. candidus and D. m. tenuirostris. It can be assumed that in some areas of SO, an intergradation zone of D. m. major and D. m. tenuitostris may also exist. A comparative analysis of the features of location and use of anvils by the GSW was carried out based on the materials collected in 1973-1974 in Plesetsk district of AO and in 2008-2022 in 6 districts of SO. The following parameters were analysed: the choice of tree species used for anvils, the altitude and orientation of anvils, the seasons of use of anvils, the dependence of location of anvils on the altitude and diameter of the tree, types of food-containing objects, etc. The period of use of anvils lasted for 5 months (from November to March) in AO, and in SO, this was almost a year-round period. In AO, anvils (n = 43) were located on trees (67 ± 14%) and stumps (33 ± 14%). As for the choice of tree species, the GSW preferred aspens (53 ± 16%); other choices were spruce and birch. In SO, 36 GSW’s anvils were discovered. The preferred type of tree (12 species) was elm (9 anvils out of 33 located on trees). In the remaining 3 cases, the anvils were located in the objects of anthropogenic origin (a wooden telegraph pole, holes in a metal pipe, and a metal fence). The majority of the GSW’s anvils are found in the gardens. Walnut trees dominated, but woodpeckers preferred elm to arrange their anvils because of softer wood and more irregularities in the bark suitable for their placement. In general, the variety of tree species used for the GSW’s anvils was significantly higher in SO than in AO (3 and 12, respectively). Coefficients of similarity in the variety of tree species used for anvils varied from 0.07 (Kj) to 0.21 (Kk). In AO, the average altitude of the anvils was 3.3 ± 2.3 m (lim 0.2–25, SD = 5.21, n = 35, p = 0.01), median = 1 m, the share of "low" anvils (including up to 2 m high) accounted for 69 ± 15% and 50 ± 16% in SO. In SO, the average altitude of the trees (including stumps), where the anvils were located, was 8.9 ± 3.1 (lim 0.4–25.0, SD = 5.4, p = 0.001, n = 34), median = 9 m. The anvils were located on an average altitude of 2.6 ±1.1 m (lim 0.01–6.5, SD = 1.98, p = 0.001, n = 34), the median = 2.3 m, the share of "low" anvils accounted for 50 ± 16%. The differences in altitude of the anvils in the compared regions according to the nonparametric Mann-Whitney criterion are statistically insignificant (U = 523.0, p = 0.22). The altitude of the located anvils increased with the altitude of trees in both regions: in AO (p < 0.01), in SO (p >0.05; not statistically significant). In AO, the anvils were directed mostly to the east (61 ± 22%), in SO – to the south (71 ± 15%). In AO, 3 types of food-containing objects were found under the anvils (n = 1639). Spruce cones accounted for 84 ± 1%; larch cones – 7 ± 1%, and pine cones – 9 ± 1%. The GSW’s treatment of cones of various species of conifers in anvils was not equally effective. The proportion of treated spruce cones was 98 ± 1,5%, larch – 76 ± 8%, pine – only 17 ± 8%. The most difficult (inconvenient) to process were pine cones, and the easiest were spruce cones. Some trees with GSW’s anvils were also used by Crossbills Loxia curvirostra ticks and Squirrels Sciurus vulgaris. In SO, 10 types of food-containing objects were found under the anvils of the GSW (n = 2607): apricot, walnut, and plum accounted for 79 ± 1.5%. Walnut was found under 18 anvils (occurrence of 50%), apricot seeds – under 9 (25%). On average, there were 72 ± 35 foodcontaining objects under the anvil (lim 5–350, SD = 80.91, median = 42, n = 36, p = 0.01). The Pinetorum subspecies (common in SO) are in contrast to the nominative subspecies major with a longer and narrower bill, well adapted for punching holes in the strong shell of stone fruits (apricot, plum) and nuts (walnuts and almonds). For example, the thickness of an apricot kernel shell is 1.74±0.11 mm (lim 1.4–2.0, SD = 0.20, n = 37, p = 0.001), median = 1.8. On the whole, а comparative analysis of the GSW’s anvils in the North (AO) and South (SO) of the European part of Russia showed a significantly higher diversity of both tree species used for anvils (3 and 12, respectively) and processed food-containing objects (3 and 10, respectively) in SO. The results obtained are quite expected due to the significantly higher species diversity of the dendroflora of the south of the European part of Russia compared to its North. The paper contains 9 Figures, 4 Tables and 41 References.