Shallow (average depth 1 m), almost enclosed bay of Lake Mälaren, surrounded by wet, tussocky meadows which merge into drier pasture and fields. Deciduous copses overlook the bay and there is a conifer-covered hill with bare rock outcrops along the eastern edge. Only 30 ha of open water remain, the rest being choked by invasive Phragmites, Scirpus and Typha.
The IBA supports important numbers of passage wildfowl, and the surrounding arable land is an important feeding area. Species of global conservation concern that do not meet IBA criteria: Anser erythropus (up to 5 passage birds), Crex crex (1-3 breeding pairs) and Gallinago media (5-10 passage birds).
BirdLife International (2020) Important Bird Areas factsheet: Lake Hjälstaviken. Downloaded from http://www.birdlife.org on 09/07/2020.