Archaeological investigation of long barrows has been hindered by the misidentification of other features. Long barrows have been confused with coniger mounds and rabbit warrens, sometimes termed pillow mounds, which can take on a similar shape. Rifle butts can also sometimes take on shapes similar to those of long barrows. Later landscaping has also led to misidentification; the two mounds at Stoke Park in Bristol, southwest England were for instance thought to be long barrows until an excavation in the 1950s revealed that they post-dated the Middle Ages, and thus must have been created by more recent landscaping projects. In areas which were previously impacted by glaciation, moraine deposits on valley floors have sometimes been mistaken for long barrows. At Dunham New Park in Cheshire, northwest England, for instance, a mound was initially believed to be a long barrow and only later assessed as a natural feature. Damage sustained by Neolithic long barrows can also lead to them being mistaken for other types of monuments, such as the oval barrows and round barrows which are usually of later date.