At the greatest extent of the last glacial period around 18,000 years ago, southern Europe was characterised by cold open habitats, and the Alpine chough was found as far as south as southern Italy, well outside its current range. Some of these peripheral prehistoric populations persisted until recently, only to disappear within the last couple of centuries. In the Polish Tatra Mountains, where a population had survived since the glacial period, it was not found as a breeding bird after the 19th century. In Bulgaria, the number of breeding sites fell from 77 between 1950 and 1981 to just 14 in the 1996 to 2006 period, and the number of pairs in the remaining colonies were much smaller. The decline was thought to be due to the loss of former open grasslands which had reverted to scrubby vegetation once extensive cattle grazing ceased. Foraging habitat can also be lost to human activities such as the construction of ski resorts and other tourist development on former alpine meadows. Populations of choughs are stable or increasing in areas where traditional pastoral or other low intensity agriculture persists, but are declining or have become locally extinct where intensive farming methods have been introduced, such as Brittany, England, south-west Portugal and mainland Scotland.