The Iconic Cry of the Fish Eagle

An African fish eagle in the Chobe National Park.

The African wilderness has many evocative sounds. The lion’s roar just before the dawn, the eerie hyaena’s chilling ‘laugh’ deep in the night, the zebras rather surprising bray/bark. The distinctive wailing call of a black-backed jackal as the sun goes down, answered almost immediately by family members. The “Good Lord deliver us” cry of the fiery-necked nightjar. The burbling, liquid call of the Burchell’s Coucal or ‘Rainbird’ just before the rains. The intense hi-pitched buzz of cicadas on a hot day. But for me, the most iconic of wilderness sounds is the call of the African fish eagle. 

Whilst one of the highest-density populations of African fish eagles is found on the banks of the Chobe River (where the images were taken), these beautiful birds range over most of the African continent – their lonely, plaintive calls echoing from the southern regions of Mauritania, Mali, Niger, Chad and Sudan, to the southernmost tip of Africa. 

They are most often spotted perched on a comfortable branch, and their loud, distinctive call reverberates over rivers, lakes, reservoirs, lagoons, swamps, rain forests, and marshes. They remain in their habitat year-round and lead a relatively sedentary lifestyle. They are diurnal, meaning they are most active during the day.  

A pair of African fish eagles displaying ‘typical’ behaviour.

Descendants of an ancient sea eagle lineage, the scientific classification of the African fish eagle, Haliaeetus vocifer, is derived from the ancient Greek words hali, “at sea” and aetos, “eagle”. “Vocifer” refers to the vociferous call of this African eagle, and was named by the French naturalist François Levaillant, who called it ‘the vociferous one’.

African fish eagles are monogamous and mate for life. The pair builds and maintains their nest using twigs and other pieces of wood, which they construct on tall trees. The nests can grow quite large, reaching as much as two metres across and just over two metres deep. Nest building is a gradual process and typically takes 10 – 20 years to get this large. New nests take up to two months to build, whereas an old nest can be refurbished in a few weeks. Each year the existing nest is spruced up with new materials placed on the old, resulting in some of the largest bird nests in the world. 

Their distinctive dark eye can be seen here – compare to the image below…

Reproduction occurs during the winter months. Females lay one to four eggs (usually two), and the couple takes turns incubating while the other hunts. The incubation period is 42 to 45 days, after which the chicks hatch and fledge around 70 to 75 days later. The parents will care for their young for three months after they leave the nest, but when they become nomadic, they congregate in groups away from adult eagles. Their life expectancy is between 12 and 24 years.

These birds are highly territorial all year round, and will even protect their airspace, calling if other birds fly by, and taking flight if their airspace is violated. They either escort the intruder across the airspace, or more typically attack them from below. In an aggressive flight they catch each other by their feet and cartwheel down, either letting go just before hitting water/ground, or sometimes crashing. Some of these attacks end in death. This behaviour is not about courtship or some other display, but purely a territorial dispute.

The nictitating membrane is a transparent or translucent third eyelid. It is largely transparent, and it helps keep the eye moist and clean while guarding it from wind, dust, and hazards. In this image you can see it over the African fish eagle’s eye.

The African fish eagle has a well-formulated hunting plan: initially observe from the high ground, swoop in and grab the fish. Every now and then the fish is too large, and alternatives are required. The first option is to fly just above the water and drag/plane the fish to the shore. When the fish is too large even for this, the eagle swims the fish to shore, using ‘butterfly stroke’. Kleptoparasitism is a feeding strategy where one animal deliberately steals food from another, and these eagles also engage in this behaviour – stealing food from Goliath herons in particular. They have a hook-shaped beak to catch and kill their prey, and their feet have powerful talons and rough soles for picking up and holding onto slippery fish. At times they forsake their piscivorous diet for any number of vertebrates, and feed on baby crocodiles, lizards and frogs, hyraxes, monkeys, hares and guineafowl. They are not above relieving locals of their chickens and will even feast on flamingo and other water birds if there is nothing else available. An African fish eagle can carry prey up to 10 times its own body weight! These birds have very few enemies, but their eggs and chicks are vulnerable to being stolen and eaten by snakes, Nile monitors, and monkeys. They also compete for food with the tawny eagle.

In some African cultures, the fish eagle is believed to possess mystical powers and has been revered for centuries as a symbol of power, strength, and purity. The eagle is also celebrated in various folklore and traditional beliefs and is even considered a sacred bird, or a messenger of the gods, by some. It is the national bird of Malawi, Namibia, Zambia, Zimbabwe and South Sudan. It is also found on the coat of arms of many of these countries.

Coat of arms displaying the African fish eagle (left to right): Malawi, Namibia, South Sudan and Zambia.

These incredible birds are a symbol of our wilderness, and it is a privilege to hear their call. It is particularly exciting to hear it in suburbia, where a pair may have made their home at a local dam/lake. So popular is the sound, that there is now even a ringtone mimicking the call of the birds. Summer is here, and the holidays are nigh. Take some time, get into the fresh air and find a pair of these magnificent birds to observe!

Jacqui Ikin & The Cross Country Team 

INFO BLOCK:

African Fish Eagle Call:
https://www.youtube.com/watch?v=LdCazQJFbPw

Goliath Heron vs African Fish Eagle (Action begins at around 3.30)
https://www.youtube.com/watch?v=_c24Tqx8SyQ

Eagle Plucks Prey in Flight | A Perfect Planet | BBC Earth
https://www.youtube.com/watch?v=DW-BSDZ7iqc

Fish Eagle Hunting Flamingos (Narrated by David Tennant) – Earthflight – BBC One
https://www.youtube.com/watch?v=2BqV2Adr3hI