A shallow, tidal bay just south of Keflavík airport. The village of Hafnir, on the bay, has a harbour.
In winter there is also a wide variety of other coastal waterbirds, including Aythya marila (100; one of two flocks in Iceland) and Calidris maritima (c.300).
BirdLife International (2020) Important Bird Areas factsheet: Ósar. Downloaded from http://www.birdlife.org on 04/12/2020.