Secretary is a bird of prey that hunts on foot. It stands 1.2 meters tall on long crane-like legs, walks up to 30 kilometers per day across African savanna, and kills venomous snakes by stomping on them with a strike force that has been measured at 195 Newtons, delivered in 15 milliseconds. The strike is too fast for the snake to respond to. By the time the venom apparatus can engage, the bird has already lifted its foot and struck again.
The legs are the weapon. The feathers on the lower legs provide some protection against bites, but the primary defense is speed. A secretary bird does not give a puff adder time to strike back. It stamps, steps away, stamps again, repeating until the prey is dead or stunned enough to swallow. Large prey is sometimes carried into the air and dropped from height onto hard ground to finish the job.
The name comes from the crest of long black feathers at the back of the head, which early European observers thought resembled the quill pens that secretaries tucked behind their ears in the nineteenth century. The bird itself is indifferent to the etymology. It has snakes to kill.
Despite its dramatic hunting method, the secretary bird eats a wide variety of prey including insects, lizards, small mammals, and eggs, with snakes making up a smaller proportion of the diet than its reputation suggests. It is an opportunist that happens to have developed a technique for handling prey that would kill most other birds.
The Nest
Secretary birds build large flat nests of sticks at the tops of acacia trees, returning to the same nest year after year and adding material each season until the structure can reach 2.5 meters in diameter and 30 centimeters in depth. Both parents incubate the eggs and feed the chicks, which remain in the nest for approximately 80 days before fledging.
The nest’s elevated position gives the adults a commanding view of the surrounding savanna, and secretary birds have been observed using their nest as a vantage point for locating prey before descending to hunt. The combination of aerial surveillance and ground hunting is unusual among raptors, most of which hunt either from the air or from a perch.
Declining Across Its Range
The secretary bird is listed as Endangered on the IUCN Red List, with populations declining across sub-Saharan Africa due to habitat loss, agricultural expansion, and the degradation of the open grassland and savanna it depends on. It requires large areas of intact grassland to maintain the walking distances its hunting strategy demands, and fragmented landscapes with roads, fences, and agricultural fields interrupt its movement in ways that reduce hunting success.
Surveys conducted across its range by the Endangered Wildlife Trust in South Africa have documented declines of over 50% in some areas over the past three decades. The bird that kills snakes by kicking them faster than they can respond is losing ground to a threat it cannot kick.