Some expert jumpers, like tiny tree frogs, use a mechanical trick to boost their jumps: instead of relying on sheer muscle power to take off, they store and release elastic energy to provide extra power during a jump. Havalee Henry, David Ellerby and Richard Marsh now report that helmeted guinea fowl use a similar elastic storage mechanism to help them get airborne(p. 3293).
Guinea fowl are reluctant flyers; they spend most of their time scurrying around on the ground. But in desperate situations, the birds resort to a rapid takeoff by leaping into the air. Marsh and his team examined how the birds power their jumps. The obliging birds were happy to launch themselves off a force plate, encouraged by the prospect of a juicy cricket after each successful jump, while the team captured the birds' leaps on high-speed video. To calculate the power produced by the birds' leg muscles, the team tracked the position of each bird's centre of mass by painting markers onto the birds and analysing the markers' positions in successive video frames. They confirmed these calculations using the forces recorded by the force plate as the birds took off.
Marsh's team measured peak power outputs of nearly 800 W kg–1 of leg muscle during the birds' jumps, which is far beyond what a bird's muscles can deliver; the team calculated that a jumping guinea fowl's leg muscles produce 330 W kg–1. Yet, clearly,the birds still managed to leap enthusiastically off the force plate. The team concludes that guinea fowl store elastic energy in their tendons, which is released during a jump to help the birds get off to a flying start.