Vransko Lake Nature Park represents a unique wetland area on the Croatian coast. Its vast reed beds and narrow belt of floodplain grasslands spread throughout the ornithological reserve are most valuable in terms of biodiversity, and these areas are also important bird habitats. In addition to the reed beds and floodplain grasslands, a wide range of different habitat types can be found in the park.
The greatest value of this area is the ornithofauna. A total of 234 species of birds have been recorded, and of these, 102 species nest within the park boundaries. This area is of international importance as a resting and feeding area for migratory birds.
Namely, populations of 140 bird species from central, northern and eastern Europe use this area as a stopover on their annual migration routes. According to some estimates, between 20,000 and 200,000 migratory birds inhabit the park area each day during the autumn migration, while occasionally this figure increases to 400,000 birds.Vransko Lake is also a very important wintering and nesting ground, especially for wetland bird species. The reeds in the ornithological reserve represent the only nesting groups for herons in the Mediterranean part of Croatia. This is a regular nesting ground for the purple heron Ardea purpurea, while other heron species can also be found nesting here occasionally.