What type of sea gull is brown and white?

The brown and white sea gull you're likely referring to is the Western Gull (Larus occidentalis). This species typically has a mix of dark brown or grayish-brown plumage on its head and back, contrasted with white underparts. Juvenile gulls also exhibit a mottled brown appearance, which can make them look similar. Other brown and white gulls include the Heermann's Gull, known for its striking gray body and white head.