The Kasari River delta area is part of the Matsalu nature reserve. The delta is rich in nutritious sediments, covered by extensive reed and bulrush thicket. The reeds make the eastern part of the Matsalu Bay one of the best breeding places for waterfowl in the entire Europe. Matsalu Bay with its surroundings is the largest and most plentiful stopover and moulting places of migratory birds in Northern Europe.