On the open lands of sub-Saharan Africa, the world's only terrestrial bird of prey, the long-legged secretary bird (Sagittarius serpentarius), stalks across the ground, sometimes walking as many as 20 miles in a single day in search of quarry. And when it finally happens upon a soon-to-be meal, we find that the civilized nature implied by the secretary bird's name is far from a true reflection of its actual behavior. Indeed, when it encounters prey, it stomps, kicks, and crushes the victim into submission and then swallows it whole.
The secretary bird, which looks a little like a cross between a chicken and a crane in shape, is thought to have been named for the raised crest of black feathers on its head, which give it an appearance reminiscent of the way secretaries once carried their quill pens behind their ears. The species' Latin genus name, Sagittarius, means “archer,” which may refer to the arrow-like feathers in the bird's crest. But while the secretary bird cuts a distinct, and notably unusual, profile among birds of prey, its common name might not actually have any relation to its appearance. Rather, it may be derived from its behavior. In Arabic, saqr-et-tair, which sounds like the French secrétaire (or secretary), means “hunter-bird,” and this derivation may have led to the common name, secretary bird.
Secretary birds inhabit grasslands, savannas, open clearings in forests, and semi-desert areas from Senegal in western sub-Saharan Africa to Ethiopia and Somalia in the east. They are also found as far south as the Cape Peninsula in South Africa and sometimes wander onto farms or into other areas inhabited by humans, where they stalk and kill small domestic animals such as chickens. More often, however, secretary birds eat insects and small mammals, and when the opportunity arises, they may consume hares, amphibians, snakes, crabs, and even other birds or their eggs.
Although secretary birds are nonmigratory, environmental conditions such as rain and fire influence their nomadic movements. For example, during a wildfire, the birds will linger near the fire's edge, capturing small animals as they flee from the heat. The typical hunting strategy they employ, however, entails flushing prey out of hiding by stamping on small mounds of vegetation. The bird then uses its bill and feet to strike or stun the prey unconscious so that it can then swallow the victim all at once.
Secretary birds are relatively widespread across sub-Saharan Africa, and those that occur within protected areas are safe from threats such as habitat loss. In some places, the species has benefited from the clearing of land for agriculture. Hence, the “marching eagle,” this terrestrial bird of prey, likely will continue to tread across Africa's open plains for decades to come.
Kara Rogers is a freelance science writer and senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is a member of the National Association of Science Writers and author of Science Up Front on the Britannica Blog. She holds a Ph.D. in Pharmacology/Toxicology, but enjoys reading and writing about all things science. You can follow her on Twitter at @karaerogers.
This post also appears on the Britannica Blog.