The site comprises the Narew river valley between the drained Wizna marshes and the town of £om¿a. The valley is narrow (up to 1.2 km wide) and deeply cut into the plain, with a close to natural character. The valley bottom is covered mainly by peat, to varying depths. There are yearly floods, especially in spring. Flood-plain vegetation includes submerged waterweed (e.g. Potamogeton), reedbeds Phragmites, meadows, sedge-beds, dry sandy grassland, and fragmented forest of alder Alnus. Valley slopes are covered with oak Quercus forest, above which is patchy dry-ground forest of lime Tilia and hornbeam Carpinus.
A total of 178 species have been recorded, including 125 breeders. Breeding species of global conservation concern that do not meet IBA criteria: Haliaeetus albicilla (one pair), Crex crex.
BirdLife International (2020) Important Bird Areas factsheet: Narew river gaps. Downloaded from http://www.birdlife.org on 09/07/2020.