The island's name is derived from the Old English fugla-næss, with fugla (modern fowl) meaning of birds and naess being the Germanic word for promontory, and it remains an important centre for birds, with the area around Foulness Point designated as a Site of Special Scientific Interest (SSSI). Habitat is provided by extensive mud flats and sand flats, which are covered twice a day by the tides, together with salt marshes, banks of shingle and shells, grazing marshes, rough grass and scrubland. They are recognised as being internationally important for six species of birds. Thousands of dark-bellied brent geese arrive from Russia to spend the winter on the flats, which are also frequented by bar-tailed godwit, grey plover, red knot, oystercatcher and redshank. For waterfowl, principally curlew, dunlin and shelduck, the site is of national importance. In winter, hen harriers can be seen foraging, and a wide range of plants and invertebrates thrive there.