 It was formerly sometimes considered to be a subspecies of the silver gull ("C. novaehollandiae"), and, as is the case with many gulls, it has traditionally been placed in the genus "Larus" but is now placed in the genus "Chroicocephalus".About one half of the total population, currently estimated at about 30 000 birds, are within the Greater Cape Town area.It breeds in large colonies, and the main traditional breeding colony for the Cape Town area is on Robben Island.