The lake is fed by nutrient-rich springwater and has a high abundance of aquatic insects (Chironomidae) and Cladocera that form an attractive food supply for ducks.
Fifteen species of ducks breed at the site, the largest such number in Europe.
The duck species composition is unique, with a mixture of European and North American species, and also of boreal and arctic species.
Most of the ducks are migratory, arriving in late April – early May from north-western Europe.
The commonest species at the lake is the tufted duck with 6,000 pairs present, whilst the second most abundant species is the greater scaup with 1,500 pairs.

Other common species include the Barrow's goldeneye, 700 pairs of red-breasted merganser, 1000 pairs of Eurasian wigeon, around 300 pairs of gadwall, 200 pairs of mallard, around 350 pairs of common scoter, 150 pairs of long-tailed duck and 75 pairs of Eurasian teal.
The northern shoveler northern pintail also regularly breed at the lake, albeit in smaller numbers, whilst common pochard used to breed regularly, but they have not done so regularly since the 1950s.
The outflowing Laxá river contains around 250 pairs of harlequin duck and there is a large colony of eider at the river mouth some 50 km away from Lake Mývatn.
 The Barrow's goldeneye and the harlequin duck are both nearctic duck species.
 The population of the Barrow's goldeneye (of about 2000 individuals) relies entirely on the habitat provided by the Mývatn-Laxá water system and its surrounding lava fields.
Most of the Barrow's goldeneyes overwinter there, using ice-free areas kept open by emerging spring water (both warm and cold) and in the strong river current.
This species is a hole-nester, in North America using tree-holes, but at Mývatn the birds use cavities in the lava for nesting.
The other duck species nest abundantly in the numerous islands of the lake and the surrounding marshlands.

Other common waterbirds include the Slavonian grebe, red-necked phalarope, great northern diver, red-throated diver and whooper swan.

The lake is included in an important bird area.

Bird populations have been monitored annually since 1975 by the Mývatn Research Station.
There is a long tradition of harvesting duck eggs for home use on the local farms.
To ensure sustainability, the harvesting follows strict age-old rules of leaving at least four eggs in a nest for the duck to incubate.

The lava flows and moorlands surrounding the lake are home to rock ptarmigans and occasionally gyr falcons may be present.
The lake is fed by nutrient-rich springwater and has a high abundance of aquatic insects (Chironomidae) and Cladocera that form an attractive food supply for ducks. Fifteen species of ducks breed at the site, the largest such number in Europe. The duck species composition is unique, with a mixture of European and North American species, and also of boreal and arctic species. Most of the ducks are migratory, arriving in late April – early May from north-western Europe. The commonest species at the lake is the tufted duck with 6,000 pairs present, whilst the second most abundant species is the greater scaup with 1,500 pairs. 
Other common species include the Barrow's goldeneye, 700 pairs of red-breasted merganser, 1000 pairs of Eurasian wigeon, around 300 pairs of gadwall, 200 pairs of mallard, around 350 pairs of common scoter, 150 pairs of long-tailed duck and 75 pairs of Eurasian teal. The northern shoveler northern pintail also regularly breed at the lake, albeit in smaller numbers, whilst common pochard used to breed regularly, but they have not done so regularly since the 1950s. The outflowing Laxá river contains around 250 pairs of harlequin duck and there is a large colony of eider at the river mouth some 50 km away from Lake Mývatn.  The Barrow's goldeneye and the harlequin duck are both nearctic duck species.  The population of the Barrow's goldeneye (of about 2000 individuals) relies entirely on the habitat provided by the Mývatn-Laxá water system and its surrounding lava fields. Most of the Barrow's goldeneyes overwinter there, using ice-free areas kept open by emerging spring water (both warm and cold) and in the strong river current. This species is a hole-nester, in North America using tree-holes, but at Mývatn the birds use cavities in the lava for nesting. The other duck species nest abundantly in the numerous islands of the lake and the surrounding marshlands.
Other common waterbirds include the Slavonian grebe, red-necked phalarope, great northern diver, red-throated diver and whooper swan.
The lake is included in an important bird area.
Bird populations have been monitored annually since 1975 by the Mývatn Research Station. There is a long tradition of harvesting duck eggs for home use on the local farms. To ensure sustainability, the harvesting follows strict age-old rules of leaving at least four eggs in a nest for the duck to incubate.
The lava flows and moorlands surrounding the lake are home to rock ptarmigans and occasionally gyr falcons may be present.
Mývatn