Cape Gannet

The entire world population of Cape Gannets breed on six islands around the coast of South Africa and Namibia. They breed in colonies on these islands and come back to the same islands every year to lay their eggs. Gannets mate for life, and usually will occupy the same nest form year to year. Gannets breed from 3 years old, and can live for 40 years. They are efficient hunters, and prey on schools of pelagic fish (fish in the surface of the water such as sardine and anchovy, red eye and horse mackerel at times) by diving into the water at high speeds. They travel up to 300km2 to find food.
This method of feeding is called plunge-diving, and Gannets are physically very well suited for this: they have long, strong and sharp beaks and streamlined bodies that allow them to efficiently dive and capture their prey.

Gannets, like most seabirds are well suited for life at sea. They are long lived and delay breeding until they are 3 years old. This increases their chance of adapting to changes in the environment, for example fluctuating availability of their prey: sardine and anchovy

Some food is better than others, for example sardine and anchovy are highly nutritious, rich in oils and have high energy content. When both sardine and anchovy are reduced, seabirds have to find alternatives. Some seabirds, like gannets will scavenge off trawlers and feed on the hake discards from the boats.

Unfortunately, this food is lower in energy than sardine and anchovy. This means that less energy is fed to the chicks, and the chicks don't build up as many fat reserves, and are weaker when they fly making them easy prey to predators. Over a long time, we can see gannet populations falling in numbers.

Source: WWF-SA