Mälaren - Ecology

Ecology

The most common nesting birds on the skerries of Mälaren are also the most common in the Baltic Sea. After a survey in 2005, the ten most common species were found to be common tern, herring gull, black-headed gull, common gull, mallard, tufted duck, Canada Goose, common goldeneye, lesser black-backed gull and common sandpiper. White-tailed eagle, Greylag goose, barnacle goose, black-throated diver, red-breasted merganser and gadwall are less common, and some of these latter are endangered in the Mälaren area. Since 1994 a subspecies of great cormorant Phalacrocorax carbo sinensis, nests there as well. The 2005 survey tallied 23 breeding colonies with 2178 nests, of which the largest colony had 235 nests. Most experts believe the great cormorant population has peaked and will stabilize at around 2000 nests.

One of the characteristic species is the osprey which has one of its strongest presences in lake Mälaren. The osprey nests in almost all bays of the lake.

The Zebra mussel is considered an invasive species and is causing some problems in lake Mälaren.