Get to Know the Ancient Birds That Lived During the Age of Dinosaurs

These days, it’s common knowledge that birds are living dinosaurs. Victorian naturalists proposed the notion after spotting similarities between dinosaur fossils and contemporary bird skeletons. But the theory was controversial until the 1990s, when thousands of feathered dinosaur fossils were discovered. Now, it’s widely accepted that more than 150 million years ago, some vicious Velociraptor cousins shrank in size, sprouted simple hair-like strands, elaborated that plumage into wings of quill pens, and took to the skies. When the asteroid impact wiped out the canonical dinosaurs, some early avians survived and carried on their lineages. Every bird alive today is the direct descendant of extinct giant reptiles.

Yet one aspect of this story is not often appreciated. For almost 100 million years birds lived alongside their dinosaur cousins. By the end of the Cretaceous period, 66 million years ago, a remarkable array of birds thrived, gliding above Tyrannosaurus rex and foraging among Triceratops. Today, paleontologists are learning much more about these pioneering species and how modern birds arose. New fossil finds are illuminating an aviary of divers and soarers, seabirds and landbirds—painting an unprecedented picture of what it would be like to go birding in the Age of Dinosaurs. 

The First Bird: Archaeopteryx

With its sharp teeth, fierce claws, and long, bony tail, the oldest and most primitive bird in the fossil record looked like a miniature Velociraptor—until the corvid-size creature unfurled its broad wings. Archaeopteryx’s pitch-black feathers with pliable shafts fluttered in the breeze as it bounded between shrubs and bushes. 

Habitat

Archaeopteryx lived in what is now Europe at the end of the Jurassic period, when global temperatures were warmer and sea levels higher. The region had a subtropical climate and was covered by lagoons and shallow seas, dotted with many islands. All 14 fossils of the species have been found in Germany.

Behavior

While Archaeopteryx spent much of its time on the ground, it could fly. It had broad wings on its arms made up of asymmetrical feathers, which were narrower and more rigid on their leading edge. This aerodynamic structure represents a hallmark of flapping flight (and a step up from the simple feathers some “raptor” dinosaurs sported for warmth or display). Plus, the species had extra winglike structures on its legs and tail to provide additional thrust, lift, and maneuverability. While it lacked the large chest muscles that power the wings of modern-day birds, it could make short flights from island to island, where it stalked insects and other small prey.

Significance

The handful of Archaeopteryx fossils are among the greatest paleontological treasures because they capture the transition from non-avian dinosaurs to birds in action, like a freeze frame. If Archaeopteryx were known only from its bones it would likely have been classified as a Velociraptor-type dinosaur. But the discovery of Archaeopteryx’s fossilized feathery wings showed it was a proper bird, built for flight. 

Modern Match

At about 20 inches long, with black plumage and a flamboyant tail, Archaeopteryx brings to mind the brash Black-billed Magpie.

The Opposite Bird: Longipteryx

Sporting a long pincer-like beak studded with pointy teeth, Longipteryx had the mugshot of a mischievous trickster. But at only six inches long, this bird was no menace. Its broad wings and long tail feathers enabled it to fly with greater grace and stamina than more primitive birds like Archaeopteryx.

Habitat

Among the first perching birds in Earth’s history, Longipteryx was at home in the trees and mastered a new environment that birds have not left since: the forests. Whereas earlier birds were mostly landbound, Longipteryx and its close kin had feet that could grip branches tightly. The lush forests of Northeast China that these canopy-dwellers inhabited 120 million years ago were sweltering hot in the summer but cold in the winter, when flurries of snow would sprinkle this bird’s feathers with a cottony gloss. 

Behavior

You can’t always judge a bird by its bill. With long jaws that could snap shut and gnarly teeth, one might assume Longipteryx dined on meat or fish. Yet the discovery of a fossil with its last meal preserved inside its stomach showed that these arboreal aerialists ate seeds and the fruit-like structures of evergreen trees. As for the teeth, paleontologists posit that they may have allowed Longipteryx to use its beak as a weapon, similar to modern-day hummingbirds. 

Significance

Longipteryx was a member of the enantiornithines, the dominant birds during the Cretaceous period. These were the “opposite birds,” named for a skeletal quirk: The shape of their shoulder bones was the reverse of contemporary birds. All of these ancient, abundant birds died out after the asteroid hit Earth at the end of the Cretaceous. Their slower growth rates as compared to other birds, and the destruction of their forest homes by fires after the asteroid, may have spelled their doom. But don’t write off these birds as a footnote of prehistory. Enantiornithines thrived across much of the world for at least 70 million years and seized new niches that would later become crucial for modern birds’ survival—like the treetops conquered by Longipteryx.

Modern Match

The silhouette of Longipteryx, with its compact body and elongated skull, is reminiscent of a Common Kingfisher. 

The Squawking Seabird: Ichthyornis

Imagine a gull with teeth, and that is Ichthyornis. Noisy, aggressive, and feisty, these seabirds bickered over food and mates and traveled in dense flocks over open water.  

Habitat

During the final 20 million years of the Cretaceous, a vast inland sea covered much of North America. Ichthyornis swarmed the shorelines and soared over the water, leaving countless fossils across a wide swath of the continent, from Alberta south to Kansas and east to Alabama. 

Behavior

Ichthyornis was among the strongest fliers of its time. Its wings were larger than those of its contemporaries, including the “opposite bird” enantiornithines, and it had a huge breastbone with a central keel to anchor enormous wing-flapping muscles. It had teeth lining the central parts of its long jaws, and capping its mouth was a short, sharp keratin beak, which it used to grab fish while flying over the sea and snag insect prey near the coast. These social creatures weren’t shy about trying to steal other Ichthyornis’s meals—or competing for their mates. 

Significance

An ornithuromorph, Ichthyornis is a member of the line that includes living birds and their closest fossil relatives. Its large wings and flight muscles were nearly identical to those of today’s birds, and its brain was large, like in modern avians. Yet, its elongated, toothed jaw and partial beak were holdovers from earlier bird ancestors. (No birds these days have teeth.) Just as Archaeopteryx was an intermediary between meat-eating dinosaurs and birds, Ichthyornis represents an intermediary between primitive birds and contemporary ones. 

Modern Match

If we saw Ichthyornis, perhaps eyeing our ice cream or French fries as we sunbathed on the beach, we might mistake it for an American Herring Gull. 

The Cretaceous Oddball: Mirarce

At two feet tall, Mirarce was a big bird for its time. A bulky creature with robust and meaty wings, it strutted across the ground amid brutish dinosaurs—confident it could take to the skies if danger arose. 

Habitat

The only known fossils were discovered in Utah, where Mirarce lived about 75 million years ago in a hot and humid jungle dominated by many species of meat-eating, horned, and duck-billed dinosaurs. Back then, this part of North America was on the fringes of the still-forming Rocky Mountains, crisscrossed by ferocious rivers draining the peaks. 

Behavior

Mirarce was a jack-of-all-trades. Its sturdy legs allowed it to navigate brush and mud as it hunted for small birds and reptiles to snatch with its substantial claws. At the same time, it was made for flight: Its wings were large enough to provide the lift and thrust necessary to take to the skies with ease, and its shortened tail sported aerodynamic feathers for turning and braking. This hybrid lifestyle came in handy for escaping the jaws of the large tyrannosaurs it lived alongside.

Significance

Mirarce is an avisaurid, a subgroup of the extinct enantiornithines that was prevalent in North and South America during the final few million years of the Cretaceous. The bird’s large size—bigger than some members of the Velociraptor clan—proves that not all avians living with the classic dinosaurs were small creatures that sought cover. Its unusual build also illustrates that long before modern birds diversified into ostriches, peacocks, and hummingbirds, enantiornithines in the Cretaceous were doing similar things, developing a wide range of adaptations and filling numerous ecological niches. 

Modern Match

With its stocky stature and the way it hopscotched between the ground and the air, Mirarce might give the impression of a Wild Turkey.

The Original Waterfowl: Vegavis

This ancient avian took to the water like the close duck relative that it is. Vegavis was a fast-flying honker that spent much of its time wading and swimming, occasionally leaping skyward and pirouetting through the air in graceful displays.

Habitat

Paleontologists have found all Vegavis fossils in Antarctica while working in some of the most inhospitable conditions on Earth. At the end of the Cretaceous, when Vegavis was paddling around, the region was forested, with a temperate climate. Thin layers of ice likely formed in the winter, spurring the birds to find areas of open water where they could dive, propelled by their feet, to snap up fish in their long, pointed, toothless bill. The birds lived along the shore, taking cover in inland areas during the coldest and darkest months.

Behavior

Vegavis lived fast and loud. Its bones had no growth lines, indicating that a hatchling reached adulthood within one year at most, like many modern birds. It had a big brain and keen senses. It could also vocalize. One remarkable fossilized Vegavis skeleton had remnants of a syrinx, or voice box—a soft tissue structure that isn’t typically preserved. Similar in size and shape to those of modern-day aquatic birds like ducks, the organ revealed that Vegavis was probably a quacker and a honker. It may have used these calls to warn of danger, woo mates, or defend territory.

Significance

Vegavis is one of the oldest known modern birds and actually a member of the same subgroup that includes today’s ducks, geese, and chickens. Although Vegavis itself did not endure the asteroid impact, some of its close relatives did. These survivors were the ancestors of today’s waterfowl. Why were these birds able to persist when so many others died? They were small (at least compared to T. rex and Triceratops), grew quickly, and their strong flying and diving abilities would have allowed them to escape immediate danger and take refuge as wildfires raged, forests burned, and earthquakes and volcanoes went into overdrive. Though Vegavis blinked out long ago, it offers clues about the factors that allowed select birds to emerge from the Cretaceous and evolve into the 10,000-plus species alive today. 

Modern Match

Common Merganser, or really any duck. Vegavis looked like a duck, grew like a duck, swam and dove like a duck, and quacked like a duck, after all. 

This story originally ran in the Winter 2025 issue as “Birding in the Age of Dinosaurs.” To receive our print magazine, become a member by making a donation today.