Storks: The Danube Basin and adjacent parts of Burgenland and Lower Austria are the second largest breeding area (after the North German Plain) of the white stork (Ciconia ciconia) in Central Europe. The first international census of 1934 revealed that storks had not settled in this area in larger numbers until the late 19th and early 20th centuries. In 1934, there were 77 breeding pairs; by 1962, at the time when the stork population was declining rapidly in the rest of Central Europe, their number had increased to 393 pairs in eastern Austria. As their number rose, storks also started breeding in large parts of Styria (first evidence of a breeding pair in 1928, 85 pairs in 1962). A few pairs also bred temporarily in Carinthia; currently storks breed in Vorarlberg, Styria, Burgenland and Lower Austria. They return from southern Africa in March and leave Austria in August. Storks' nests on chimneys are a characteristic landscape feature, especially in Burgenland. In recent years, there has been a dramatic decline in the stork population on account of the reduction of grassland suitable for feeding. The only Central European breeding colony where storks still build their nests in trees, which was their original breeding behaviour, is near Marchegg, Lower Austria. Side by side with the white stork, there are also some rare black storks (Ciconia nigra) that breed in Carinthia, Styria, Upper Austria, Burgenland and Lower Austria. Since1948 Austrian ornithologists have ringed young storks in order to study their migration.