Tropicbirds are master aviators that cannot walk, yet they rule the open ocean

Nature · Published 3 October 2026 Swipe more like this →

In short: These elegant, white-plumaged seabirds are the only surviving members of their unique biological order. With legs positioned so far back on their bodies that walking is impossible, they spend their lives in the air or at sea, performing complex aerial courtship rituals before nesting in remote, rocky crevices.

Tropicbirds, belonging to the family Phaethontidae, were long misclassified alongside pelicans and cormorants. Modern genetic research, including a 2014 whole-genome analysis, has corrected this, revealing they are actually distant relatives of the sunbittern and kagu. Their distinct evolutionary path is further supported by microscopic eggshell studies conducted by Konstantin Mikhailov in 1995, which show they lack the thick microglobular layers found in other water birds.

The genus Phaethon, named by Carl Linnaeus in 1758, contains three species: the red-billed, red-tailed, and white-tailed tropicbird. The red-billed species is considered the most ancient, having diverged from its relatives approximately six million years ago. These birds are specialized for a pelagic lifestyle, hunting by plunging into the surface of the ocean to catch flying fish and squid. Because they must travel vast distances to find food, they have evolved to lay a single egg, a strategy that allows them to manage the challenges of an unpredictable, open-ocean environment.

Their physical design is entirely optimized for flight rather than terrestrial movement. With wingspans reaching up to 112 cm and elongated tail feathers, they are built for agility. On land, however, they are clumsy, unable to walk and forced to push themselves forward using their webbed feet. During breeding, they engage in spectacular group displays, flying in vertical circles while swinging their tail streamers. Once a pair is formed, they share incubation duties for 40 to 46 days, with the male often providing food for the female until the chick hatches.

The chicks grow slowly compared to nearshore birds, accumulating fat deposits that sustain them during the long intervals between feedings. After fledging, which occurs about 12 to 13 weeks after hatching, the young birds often spend several days floating on the ocean to shed weight before they are light enough to take flight. This unique life cycle reflects a deep adaptation to the demands of life far from the coast.

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