The mouth of the Rhine into Lake Constance forms an inland delta. The delta is delimited in the West by the Alter Rhein ("Old Rhine") and in the East by a modern canalized section. Most of the delta is a nature reserve and bird sanctuary. It includes the Austrian towns of Gaißau, Höchst and Fußach. The natural Rhine originally branched into at least two arms and formed small islands by precipitating sediments. In the local Alemannic dialect, the singular is pronounced "Isel" and this is also the local pronunciation of Esel ("Donkey"). Many local fields have an official name containing this element.