The First Known Bird May Have Hopped Like a Crow to Take Off

A crow crossing a lawn rarely leaps straight into flight. It hops once, twice, gathering speed before its wings ever take over. New research suggests the first known bird got airborne much the same way. Archaeopteryx, the 150-million-year-old fossil at the center of the debate over how flight began, likely couldn’t reach flying speed in a single leg-powered leap. Instead of one explosive launch, it may have needed two or three hops in a row to build up enough speed to fly.

That distinction matters more than it might seem. Modern birds like sparrows and doves use one explosive leg push to rocket into the air, a move that demands strong shoulders and a chest built for powerful wingbeats right from the start. Archaeopteryx lacked those features. Its shoulder joints couldn’t rotate the way a pigeon’s can, and it had no keel-shaped breastbone, the anchor point modern birds use for their flight muscles. For years, that mismatch has puzzled scientists: how could something that looks like it should barely get off the ground be considered a bird at all?

Researchers at the University of Southampton and colleagues in France, writing in the journal Developmental Biology, tested whether Archaeopteryx’s legs alone held the answer. Rather than relying on guesswork, they built a detailed computer model of its hip, knee, and ankle joints, borrowing motion and force data from birds alive today, and used it to calculate how fast this ancient animal could have pushed itself off the ground using nothing but its legs.

How Scientists Modeled Archaeopteryx’s Legs

Since nobody has a living Archaeopteryx to study, the research team built one from scratch, digitally. They started with an existing computer model of bird leg muscles and reshaped it to match Archaeopteryx’s proportions and bone lengths, based on measurements from well-preserved fossil skeletons. They settled on a body weight of 400 grams for their model, close to published estimates based on the length of its arm and leg bones and in the middle of the range scientists have proposed over the years.

One detail shaped their thinking from the start: Archaeopteryx’s legs made up about 13 percent of its total body weight, noticeably more muscle mass than the 9 to 10 percent typical of birds flying today. That strongly suggests its legs, not its wings, did the heavy lifting during takeoff.

To figure out how those legs actually moved, the team turned to a living stand-in. They used detailed motion-capture data from zebra finches jumping into flight, then adjusted the joint angles and rotation points to fit Archaeopteryx’s different leg proportions. They also checked their results against jumping data collected from a crow, since crows are close in size to Archaeopteryx and use exactly the kind of step-by-step, multi-hop takeoff the researchers suspected the ancient bird relied on.

From there, the model calculated how much force and twisting power each joint would need during a takeoff leap, then compared that to how much force Archaeopteryx’s leg muscles could actually produce. The team deliberately left out any help from wing flapping during the initial push off the ground, choosing to test the toughest possible scenario for the legs alone. If the legs could handle takeoff even without any wing assistance, that would be strong evidence the strategy was mechanically realistic.

What the Archaeopteryx Takeoff Model Revealed

Using this setup, the researchers tested three scenarios: a single all-out leap like modern birds use, a series of jumps with no wing help, and a mix of jumps interspersed with light flapping.

A single leap wasn’t enough to reach sustainable flight speed. Archaeopteryx’s legs, according to the model, could generate about 2.98 meters per second on a single jump, well below the roughly 7 meters per second scientists estimate as the minimum for sustained flight. In that scenario, the bird would still leave the ground and follow a short arc through the air on wing lift, but it couldn’t build the speed to keep flying. That gap has made a one-leap takeoff seem implausible for this animal.

Multiple jumps closed that gap fast. If Archaeopteryx skipped wing flapping entirely and relied purely on its legs, three consecutive jumps would carry it to a speed of 6.66 meters per second, just shy of minimum flight speed, at which point modest wing thrust could bring it to sustainable flight speed in about 0.23 seconds. Alternatively, if it added a light wing flap between just two jumps, it could reach 6.25 meters per second after the second leap, then reach sustainable flight speed after about 0.36 seconds of flapping.

Throughout these simulations, one joint kept showing up as the bottleneck: the ankle. Peak force demands were highest at the ankle joint, and it was the ankle muscles’ limited capacity, not the knee or hip, that capped how fast Archaeopteryx could have jumped. That lines up with previous research on living birds, which has also found ankle strength to be the critical factor in jumping performance.

Researchers also checked how much their results depended on uncertain details, like exactly where Archaeopteryx’s center of balance sat in its body, or precisely where its foot pressed against the ground during a jump. Even accounting for that uncertainty, the estimated maximum takeoff speed stayed between about 2.58 and 3.12 meters per second, not enough to change the conclusion that multiple jumps, not one, were the answer.

Rewriting How Archaeopteryx Learned to Fly

These results reshape a long-standing puzzle about how flight evolved. Rather than needing to evolve powerful shoulders and a rocket-launch leap right out of the gate, the earliest birds may have used a much more forgiving strategy: run, jump, jump again, and work up to flying speed the way a plane taxis and accelerates down a runway instead of leaping straight up. Wing flapping, on this model, would have kicked in as a supplement to gradually increase speed rather than the powerful, primary source of thrust it is in modern birds.

This lines up with something already visible in nature today. While many small birds use one explosive leg leap to get moving, corvids, the family that includes crows and magpies, often hop several times with only minimal wing involvement before really taking off, especially when they’re not in a hurry or under threat. Archaeopteryx, close in size to a magpie, may have been doing something very similar 150 million years ago.

None of this proves exactly how Archaeopteryx got off the ground. Fossils can’t record behavior directly, and any biomechanical model is a best estimate built from incomplete evidence. But the numbers line up cleanly: relatively robust hindlimbs, joint demands that stayed within what those muscles could produce, and a jumping pattern that mirrors what some birds still do today. Archaeopteryx probably wasn’t launching into the sky in one graceful bound. It was hopping its way there, one leap at a time, until it finally built up enough speed to take off for good.