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Martin Spiess, Hans Schmid, Toni Fankhauser, Frank Borleis, Thomas Sattler

Ausbreitung und Bestandsentwicklung der Saatkrähe Corvus frugilegus in der Schweiz 1963–2019.

2023

120

164–177

Key words
(von 1994 bis 2006 vergeben)

Bestandsveränderung, Arealveränderung

Schlagwort_Vogelart
(wissenschaftlich)

Corvus frugilegus

Schlagwort_Vogelart
(deutsch)

Saatkrähe

deutsch

Abhandlung

Distribution and population trends of the Rook Corvus frugilegus in Switzerland 1964–2019 – The Rook bred in Switzerland for the first time in 1963 in the western Central Plateau and in 1964 in Basel. At first, it spread slowly in the immediate vicinity of these founding pairs, then the Central Plateau was colonised in both main directions. From there, the spread along the main axis of the Central Plateau gained momentum from the 2000s at the latest. Secondary dispersal took place along large rivers. In the meantime, the species has reached the eastern border of the country and colonised the Rhone Valley in Valais. Initially, the population increased only slowly. 100 pairs were only reached after 20 years. The 1000 mark was surpassed in 1998. The population increase continued and in 2019 8420 pairs were counted. Only a few rookeries recorded a slight decrease between 1993–1996 and 2017–2019. The number of breeding colonies developed similarly: in 1980, there were only ten rookeries. Then in 2019, a peak was reached with 395 colonies. Like the population trend, the number of colonies has also increased exponentially since 1963. The largest rookeries remained mostly below 20 pairs until 1975. Until the mid-1980s, their size first increased linearly to a maximum of 80 nests. It was not until 2005 that the maximum colony size increased sharply, reaching a peak of 233 nests in 2013. The average colony size – after an initially rapid increase – remained quite stable from the end of the 1960s onwards, despite some fluctuations. The proportion of colonies in the settlements increased over the years from 76 to 85%; in the agricultural area, the proportion of colonies decreased accordingly. Urban trees and avenues have always been the most important nesting sites for rookeries. The colonisation and original increase of the Rook in Switzerland is probably related to the range expansion in Germany and France. Most rookeries are found in settlements, which regularly leads to conflicts with the residential population. Despite scaring-off campaigns and shooting, there are no signs of an end to the population increase and range expansion of the Rook in Switzerland.