Øra Nature Reserve lies southeast of Fredriksad, where the river Glomma meets the Oslofjord. The area is known for its rich birdlife – some 250 species have been registered here. The reserve occupies a strategic place in the main migratory path in southern Norway, and is an important resting stop for the migration in the spring and autumn. It was here that mute swans established their first home in Norway. They were observed building nests, laying their eggs and rearing their offspring on Øra as early as 1937. Wading birds and many different kinds of ducks also come here  - most common among them are whooper swans, mallards, green-winged teals, Eurasian wigeon, common goldeneyes, wood sandpipers, greenshanks, ringed plovers and dunlins. The area also attracts some endangered species, including rare seagulls.

The reserve is also of interest as the only big marine soft bottom estuary in Norway – the brackish waters in the area attract fish species usually found in both sea and freshwater. And while the inner shallows of the Øra bay are dominated by reeds and sandy creeks, the outer bay has a real marine character, with many islands and skerries further out into the Oslofjord

The area, which covers some 15,5 square km, has been a protected nature reserve since 1979, and a recognized Ramsar Wetland since 1985. It includes, among others, the islands of Hestholmen, Løvøy and Nes Ramsøy. There is a bird-watching tower there, incongrously located by a rubbish heap, affording great views of the area. The best season for bird-watching is from mid-March til May and from mid-August til the end of October.