Is it a bird, is it a plane, is it a boat?

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The African fish eagle (Haliaeetus vocifer) has been the stopping the show in sub-Saharan skies for centuries. This bird, with its attractive plumage and unmistakeable call, is one of the most recognisable and well-known denizens of lakesides all over Southern Africa. The fish eagle belongs to the genus Haliaeetus, an ancient type of sea eagle, and is most closely related to the Madagascar fish eagle, although it bears a strong resemblance to the American bald Eagle. It is not a true fish eagle – these belong to the genus Ichthyophaga.

The African fish eagle is a large striking bird, with a wingspan of up to 2.4m and a weight of about 3.6kg. Their handsome chocolate brown livery, yellow face and legs, and distinctive white head, breast and tail, set them apart from their avian fishing peers, and make them easy to identify from a distance. The female is the larger of the two sexes, and indistinguishable from the male except for a higher pitch to her call.

During the breeding season, a mating pair will exchange pleasantries with their classic 'wee-ah, hyo-hyo' sounds, which have become so well-known in the African bush.

The birds are monogamous and mate for life, with close cooperation between the breeding pair concerning hunting, defending their territory and caring for their young. They usually build two nests out of twigs, in prominent trees situated close to freshwater lakes, reservoirs, and rivers. These nests are often reused and built upon during the years, and sometimes become quite large – up to 2m across and 1.2m deep.

Breeding takes place during the dry season, and the female typically lays one to three white eggs speckled with red. The parent birds take turns incubating these, and the chicks hatch within 45 days. Most often, they are all raised successfully. At 70 to 75 days old the chicks leave the nest resplendent in a dull brown plumage, with light eyes which will darken, along with their feathers, as they reach adulthood.

Naturally, the African fish eagle's main prey consists of fish, but they are known to feed on reptiles, other birds, carrion and even small hyraxes and monkeys. Fish eagles are not averse to stealing a meal from other birds, and the Goliath heron is a favourite target for this freeloading behaviour.

Fish eagles hunt by swooping down on a fish and grasping the hapless creature in their large claws. Their toes are equipped with structures called spiricules that allow them to grab a hold of slippery prey up to 1.8kg in weight and fly off with it. Should the eagle catch a fish that is too heavy to allow it to become airborne with it, the bird simply paddles to the shore using its wings.

The sight of the fish eagle in flight is a spectacular one, but to see these adept fishermen in action is a privilege afforded only to the very patient and the very lucky.

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Tuesday, 22 May 2018