Loch Stiapabhat is a large, nutrient-rich loch in North Lewis. It is a shallow loch with an estimated maximum depth of 5m and is 7m above average sea level, covering an area of around 2.5 hectares. It is rich in nutrients due to the underlying calcareous sand and surface drainage from the surrounding crofts. A survey in 1986 recorded "an unbelievable density of three - spined Stickleback", the only fish found and a food source for many of the loch’s feathered visitors.
During the spring and autumn, the loch is an important feeding stop for a range of rare and interesting species as it lies on the main flyway from and to the Arctic. These include the Whooper Swan, Teal, Wigeon and Pink-Footed Goose. It also supports many feeding and nesting birds including those of international importance such as the Dunlin, Redshank, Golden Plover and Lapwing.
Historically, it was the only nesting site in Lewis of the Little Grebe and Moorhen and in previous years was home to the largest colony of Black-headed Gulls in the Outer Hebrides, although all of these species have suffered from mink predation in recent years.
In the summer, the Corncrake can be heard calling from the tall vegetation around the Loch which lies within the Ness and Barvas Special Protection, created to protect the Corncrake. The machair becomes a carpet of colour with birds-foot trefoil, eyebright, clovers and orchids among some of the many wildflowers that can be seen.
Loch Stiapabhat has been designated a Site of Special Scientific Interest (SSSI) and in 2005, it was declared a Local Nature Reserve - the only one in the Western Isles.
Loch Stiapabhat also has a lot of archaeological interest as it is thought that the ballast of a viking ship rests in the loch. It is said that the area North of the loch was once an island, formed after the ice age when sea levels rose. When the ice retreated, the weight of it was lifted and the land rose. As it did, the sea receded and the loch was created. Its name is said to mean 'the loch of immersing or soaking' and is thought to relate to the practice of soaking flax prior to spinning.