This sleek seabird forages typically less than ten kilometres from shore, in the cool waters of the north-flowing Benguela Current (6). It feeds in vast flocks of thousands of individuals on shoals of fish, often in association with terns, penguins and gannets. With a little leap clear of the water’s surface, the Cape cormorant dives into the ocean (3), the surface feathers of its glossy plumage becoming easily soaked, reducing buoyancy and allowing the cormorant to descend more easily into the water. The inner feathers, however, remain waterproof and provide insulation in the chilly water (4). Each dive lasts for around 30 seconds, and each day there are two feeding bouts of around 30 minutes each (3). The Cape cormorant feeds principally on pilchard, as well as anchovies, sandeels, sardines, hake and, in smaller amounts, crabs, lobsters, mussels and squid (3).
Breeding colonies of Cape cormorants are equally immense as the feeding flocks. Breeding may take place at any time of the year, but egg-laying primarily takes place between September and February. The male gathers dried seaweed, sticks, and floating ocean debris, such as plastic, netting and rope, from which the female constructs a nest, measuring about 30 centimetres across. Into this flimsy structure is laid a clutch of one to five eggs (most commonly two to three), which are laid at intervals of two to three days. Both the male and female share the task of incubating the eggs for 22 to 28 days, and when the young hatch, both bring food to the young (3). Parental care even extends to sheltering the newly hatched young from the sun, with adults observed standing with their wings outstretched with their backs to the sun (3). After five to six weeks, the young leave the nest to form small crèches of up to ten birds, and by nine weeks the young can fly (3). This fledgling population is very vulnerable to predators; Cape fur seals prey heavily on seabirds in southern Africa, and Cape cormorants are particularly susceptible to predation when they land on the waters surrounding breeding islands (7). Cape cormorants are known to live for up to nine years (3).