Hartlaub’s Gull is a gregarious species that forages, roosts and nests in large flocks. They occur in coastal areas – inshore waters less than 50m deep, estuaries, lagoons, beaches and harbours, and rarely venture further than 20km from land. Their natural diet relies in a large part on marine invertebrates associated with beached kelp, supplemented with fruits, eggs and small fish. They also frequent sewerage works, rubbish dumps and abattoirs for easy pickings.
Breeding takes place at anytime of the year, though some localities show distinct peaks in nesting activity at varying times of the year. Breeding colonies are established on flat, rocky islands, coastal pans, in harbours and even on top of buildings, where the nests are small hollows of matted plant material. Pairs are monogamous and aggressively defend a small patch around their nest. Clutches of one to three eggs are incubated by both parents for just short of 4 weeks. Chicks attain adulthood at around two years of age. Hartlaub’s Gull is closely related to the Grey-headed Gull, with which it sometimes interbreeds.
Hartlaub’s Gull occurs only in Namibia and South Africa (Northern, Western and Eastern Cape), where they are considered to be common and increasing their population. With about half of the estimated 30,000 adults in the population occurring in and around the Cape Peninsula, Table Mountain National Park is a good place to look for Hartlaub’s Gull. The IUCN lists the species as being of least concern, despite noting threats to their breeding success rate.