It was created in 1975 with an effort of the Rudka Forest Inspectorate. “Koryciny” Nature Reserve covers an area of 88.63 hectares in order to preserve the portion of the natural forest, characteristic of the Drohicka Upland. The reserve is characterized by a well-preserved natural stand of trees, which main components are pedunculate oak and hornbeam, and an admixture are: birch, asp and spruce. In the reserve grows "Radoslaw" oak. Its age is estimated at 460 years. The height of the tree is 35 m, a circuit is 726 cm. It is one of the highest oaks that are monuments of nature in Podlasie. The only higher one is the oak growing in the Białowieska Forest. Among the herbaceous plants there are legally protected species: daphne, bird's-nest orchid, lesser butterfly-orchid, lycopodium, wild ginger, lily of the valley, buckthorn, woodruff, guelder-rose. In the reserve and in its immediate vicinity there are 37 species of birds. It should be emphasized that in the reserve exist all species of fly-catcher and four species of woodpecker.