The real mystery is not why these birds fly, but why they bother at all. Wings are expensive hardware; in dense tropical forest, full flight is a last resort, not a default. Aerodynamic drag spikes between trunks and vines, and each burst of flapping burns through glycogen far faster than a series of short ground hops or a sprint between patches of cover.
Predators help seal that trade. A bird that stays low can freeze, blend into leaf litter, then bolt a few meters rather than trace a clean line in the air that a hawk can track. The forest floor also concentrates payoff. Invertebrate biomass, fallen fruit and seeds all settle downward, so natural selection pushes many species toward a strategy where flight becomes a rapid reset button, while routine foraging runs on tendon elasticity and efficient leg muscles.
Even reproduction bends to this logic. Courtship in some ground-inclined species plays out on logs and clearings, where short display hops and wing flicks signal fitness without the metabolic shock of sustained flight. Built to fly, these birds still obey the math of biomechanics and energy budgets, and that math keeps their feet, not their wings, in near constant use.
