An area of boreal forest (60% pine Pinus, 20% alder Alnus and 10% birch Betula stands) with large bogs (covering 40% of total area).
An important breeding area for Grus grus (the highest density in Lithuania). Breeding species of global conservation concern that do not meet IBA criteria: Crex crex.
BirdLife International (2019) Important Bird Areas factsheet: Viesvile Strict Nature Reserve. Downloaded from http://www.birdlife.org on 06/12/2019.