[4] Olrog's gull is native to the Atlantic coast of Argentina, Uruguay, and southern Brazil.

It breeds at a very limited number of colonies between 38.49° and 45.11°S, about two-thirds of which are in the estuary of the Bahia Blanca River.

At other times, it is to be seen on rocky coasts, harbours, beaches, coastal lagoons, brackish water, and estuaries.

[5] During the breeding season, Olrog's gull feeds largely on crabs, which are picked up from the exposed shore or the seabed while walking or swimming, or dipping under the surface of shallow water.

The nest is on rock, sand, or shingle and is usually lined with vegetation, but sometimes with seaweed, feathers, shells or bones.