Charakterystyka drzew gniazdowych dzięcioła czarnego w Puszczy Augustowskiej

The Black Woodpecker Dryocopus martius excavates nesting holes in big trees and use dead wood for foraging. It is considered as a key and an indicator species in the protection of biodiversity of forest ecosystems, because its cavities condition the possibility of breeding the biggest secondary cavity−nesters, bats, and some species of wasps. We studied preferences of the Black Woodpecker towards the nesting trees in the Augustów Forest (NE Poland). It is an extensive forest complex covering 114 000 ha, dominated by fresh and mixed fresh coniferous forest sites. Scots pine Pinus sylvestris occupies 78% of forest area. Stands older than 100 years cover about 18% of the study area. We searched for trees with cavities of the Black Woodpecker in stands older than 60 years. We identified tree species, their age and health condition. The breast height diameter and height of trees and height of the cavities above ground were measured. Additionally, cavity entrance orientation were estimated. We found a total number of 150 nesting trees with 229 cavities excavated by the Black Woodpecker. Pines constituted 95% of nesting trees. Cavities were found also in Betula pendula and Populus tremula. Live trees predominated among trees with cavities. Dead trees (only pines) constituted 12% of all. More than one (form 2 to 6) cavity entrances were recorded in almost 30% of nesting trees. Woodpeckers excavated cavities in pines in age from 92 to 222, 159 years old on average. Taken together, 90% of cavity pines were older than 110 years. The height of nesting trees varied from 21 to 37.5 m (30.5 m on average), and its breast height diameter was 32−96 cm with mean of 54 cm. Over 90% of trees with woodpeckers' cavities had dbh larger than 40 cm, and almost 50% between 50 and 60 cm. The mean height of cavity entrances was 12.8 (6−27) m. There was no dependence between the height of cavities and the thickness of trees. The entrance orientation was dominated by east and north (together 58%). Birds selected the least often an entrance in southwest (only 2.3%). The Augustów Forest is the only study plot in Europe, where so strong domination of pines among nesting trees of the Black Woodpecker was recorded. The preferred tree species in south and west part of the continent is Fagus sylvatica. The Black Woodpecker uses for nests mainly the oldest pines, but it is related to the thickness, and not directly to the age of these trees. The maintenance of pine dominated stands older than 120 years is necessary for the Black Woodpecker protection in the Augustów Forest.