Their amount in the surrounding is decreasing, only sometimes there is seen kite (Milvus milvus) or Pandion haliaetus, very rarely also white-tailed eagle (Halialetus albicilla). On the other hand, the amount of gulls is substituted here in many species. In Sĺňava live two species, which only sometimes fly deep into European middle-lands. They are Strercorarius parasiticus and sea gull (Larus marinus). Fro other gulls were recorded Larus Fuscus, Larus argentatus, Larus canus (common gull), Larus minutus (little gull), Rissa tridactyla and Larus ridibundus (black-headed gull). The last one – black-headed gull – lives here in two localities. Those, which nest in Sĺňava, are migrating every autumn and instead of them are coming northern populations mainly from Baltic sea. To the most interesting transmigratory birds belong thrush-nightingale (Luscinia luscinia) and red-spotted bluethroat (Luscinia suecica). Very important is also they nesting of birds in Sĺňava during the winter, because the system of draining canals provides warmer water, which does not freeze in the winter (important are also the thermal waters). Different stand have, from all the species of birds, swans. The ornithologists found out that they live in Sĺňava in year 1963 during the spring migration time. Firstly, they were just 3-4 swans in groups, which were flying through or stayed for short rest. In year 1973 there were any swans in Piešťany. The increase in their number was recorded in year 1977. In winter 1981/1982 was seen formation of winter nesting on great swans. It is interesting, that they were attracted by feeding of gulls near the Kolonádny bridge. During that times they were living mainly on the slow arm of Váh. In years 1985/1986 the amount of winter swans reached 122 pieces. In present times are Piešťany the biggest winter nesting-place of swans in Slovakia. Sĺňava is not important only because of birds. For example lives here protected and very rare and endangered Europe-turtle. On the peninsula Výsadba lives many rare species of insects. For example endangered butterfly southern festoon and sometimes we can see also praying mantis (Mantis religiosa). The smallest organisms that live in the waters of Sĺňava are microscopic mushrooms as Ephydatia fluviatlis or Spongia lacustris, leeches (Hirudo medicinalis), water-spiders (Argyronetta aquatica), from microorganisms are here common types as in other lakes or ponds – daphnia (Daphnia magna), Diaptomus vulgaris. On the bottom of the water basin are many snails and organisms living in a shell (Planorbis corneus). Insects are one of the main parts of the ecosystem of Sĺňava.