Bestandssituation des Mittelspechts Dendrocopos medius im Kanton Thurgau 1976-2005: Grundlagen für den nachhaltigen Schutz einer gefährdeten Waldvogelart.

Abstract

In 2005, all oak forests (≥ 5 ha) in the canton of Thurgau, Switzerland, were surveyed in search for Middle Spotted Woodpeckers using playback tapes. We found a total of 124 territories, of which 87 were considered to be true breeding territories, while the status of the remaining 37 territories was uncertain. The western of the two identified strongholds appeared to be well connected to populations in the canton of Zurich, while the eastern stronghold was relatively isolated. Overall, the mean distance (± SD) between occupied oak forests was 3.5 ± 1.6 km (n 17), whereas the average distance between all examined oak forests was 2.4 ± 1.1 km (n 31). Density of the Middle Spotted Woodpecker was 0.26 breeding pairs (bp) per 10 ha when considering the total area of the censused forests, and 1.48 bp per 10 ha when only oak areas were considered. Within forests, territories were preferentially located in oak-rich parts of the forests. Compared to censuses conducted in a subset of oak forests in the 1980s and 1990s, we found no changes in numbers of Middle Spotted Woodpeckers at about half of the sites. However, at sites with changes between the censuses, declines occurred significantly more often than increases. Our results suggest that the canton of Thurgau hosts an important part of the Swiss population of the Middle Spotted Woodpecker and should therefore be given high priority in terms of oak and woodpecker conservation measures.