New evidence from Alaska’s Prince Creek Formation indicates that birds were nesting in the Arctic approximately 73 million years ago, more than 25 million years earlier than previously documented. Paleontologists have unearthed over 50 bird fossils, some no larger than grains of rice, shedding light on the diversity and adaptability of Late Cretaceous avifauna in high-latitude ecosystems.
Arctic Today Versus Cretaceous Past
The modern Arctic serves as nesting grounds for more than 200 species of birds, which fulfill vital ecological roles such as pollination, seed dispersal, and the regulation of insect populations. During the Late Cretaceous, the polar regions would have appeared strikingly different: a warm, verdant landscape teeming with dinosaurs, early mammals, and now, it seems, a variety of birds.
“At 73 million years ago, the Arctic was no frozen wasteland. Summers featured six months of continuous daylight and abundant plant growth, supporting diverse food webs,” explained Lauren Wilson, first author of the new study and a doctoral candidate at Princeton University. “Our fossil evidence confirms that avian species were not only present, but actively nesting in these high-latitude climes.”
Until now, the earliest known evidence of birds nesting in polar regions dated to the Eocene epoch—approximately 46.5 million years ago—when penguin colonies thrived in Antarctica. The Prince Creek findings extend that record by more than a quarter of a hundred million years and suggest that avian polar nesting has deep evolutionary roots.
Discovery Context and Geological Setting
The Prince Creek Formation, located along the Colville River in northern Alaska, has long been recognized as a rich source of Late Cretaceous fossils, including hadrosaurs, ceratopsians, and tyrannosaurs. Rivers carved through the coastal plain deposited sediments that preserved bones and footprints alike. Beginning in the 1990s, teams led by the University of Alaska Museum of the North gradually began uncovering dinosaur remains at high latitudes.
“We always suspected that birds had to have been there, because other vertebrate groups inhabited those polar forests. But bird bones are notoriously fragile, and until our recent effort, no substantial avian remains had been found in Alaska’s Cretaceous deposits,” said Professor Patrick Druckenmiller, director of the University of Alaska Museum of the North and co-author of the study published on May 30, 2025, in Science.
Over four field seasons (spanning 2021–2024), the multinational team conducted summer expeditions under 24-hour daylight. At low-tide intervals, they methodically scraped away sediment layers along the riverbanks, painstakingly picking through sandy deposits to isolate fragments of bone.
“We literally panned for fossils the way you’d pan for gold,” Druckenmiller said. “Our tools were small brushes, dental picks, and sieves to wash sediments in water. Every time a tiny bone fragment appeared, we knew it could be part of a bird embryo or hatchling—our prize.”
Microscopic Fossils, Monumental Implications
Among the more than 50 avian specimens extracted, many measured under 2 millimeters in length. High-resolution microscopy and CT scanning revealed that some fragments belonged to embryonic or perinate individuals—minute scraps of skulls, limb bones, and vertebrae from birds that died before or shortly after hatching.
“Finding embryonic remains in situ is a strong indicator of nesting behavior,” Wilson noted. “Adult birds likely laid eggs in shallow scrapes on riverbanks or in low-lying vegetation. When eggs hatched, newborn chicks would have been preserved by rapid burial during seasonal flooding.”
By comparing bone microstructure—specifically the presence of rapidly forming woven bone and lines of arrested growth—the team determined that at least three distinct taxa of birds attended these polar nesting sites. Two specimens were identified as members of the Ichthyornithes, an extinct lineage of toothed seabird–like avians, while at least one belonged to the Hesperornithes, large, foot-propelled diving birds with teeth. Other remains likely represent early neornithines—closely related to modern crown-group birds, including duck-like, toothless species.
“The presence of neornithine characteristics—such as reduced or absent dentition—suggests these Arctic breeders were already evolving toward the morphological traits of extant birds,” said Wilson. “It underscores that the evolutionary split between modern birds and their closest extinct relatives had already occurred by the Late Cretaceous.”
Climatic Pressures and Adaptations
Reconstructing the Late Cretaceous Arctic climate requires understanding paleolatitudes, seasonal extremes, and ecosystems. Around 73 million years ago, during the Campanian stage, Earth’s mean temperature was several degrees warmer than today. The Arctic Circle lay slightly south of its present position but still experienced extended periods of continuous light in summer and total darkness in winter.
“Fossil pollen, leaf cuticles, and dinosaur tracks confirm a lush, temperate environment in the Prince Creek region. Conifer- and broadleaf-dominated forests bordered rivers that teemed with fish and invertebrates,” explained Druckenmiller. “During the Arctic winter, temperatures seldom dropped below freezing for extended periods, but darkness and limited food would have posed challenges.”
Modern Arctic-nesting birds—such as snow geese, sandpipers, and terns—cope with these extremes through behavioral and physiological adaptations. They time breeding to peak summer productivity, endure communal roosting, and engage in migratory movements. The Cretaceous avians likely exhibited similar strategies.
“Embryonic and hatchling remains suggest that these birds reproduced in the Arctic summer, when long daylight hours maximized foraging opportunities. Whether they wintered at lower latitudes remains uncertain, but partial or complete migration was highly probable,” Wilson said.
Taxonomic Diversity and Morphological Insights
Detailed anatomical study of delicate bone structures, performed with micro-CT imaging at the University of Alaska campus and Princeton’s paleontology lab, allowed researchers to assign specimens to broad clades.
- Ichthyornithes: These “toothed seagulls” combined avian and reptilian features—feathered wings, lightweight skeletons, and jawbones bearing conical teeth. Though primarily known from mid-latitude localities in Montana (e.g., the Hell Creek Formation), their presence in the Arctic signifies that these pelagic birds ranged widely.
- Hesperornithes: Foot-propelled diving birds analogous to modern loons, possessing streamlined bodies and robust limb bones. Their fossils—typically found in temperate and subtropical Cretaceous coastlines—reveal adaptation to aquatic foraging. Arctic specimens indicate that cretaceous polar waters supported rich marine food chains.
- Neornithes: Early representatives of modern bird groups, including at least one species resembling a duck or shorebird. Skull fragments exhibiting edentulous (toothless) beak surfaces and limb bones with pneumatic (air-filled) cavities reinforce their classification as crown-avian.
“Neornithine finds are particularly exciting because they place the origin of modern avifauna at high latitudes, just as dinosaurs dominated the same ecosystems,” said Patrick Druckenmiller. “These data fill a crucial gap in understanding how modern bird lineages spread and diversified during the Cretaceous.”
Ecological Integration: Coexistence with Polar Dinosaurs
The Prince Creek Formation is best known for its dinosaur assemblage—hadrosaurs such as Edmontosaurus, ceratopsians like Pachyrhinosaurus, and theropods including Nanuqsaurus. Isotopic analyses of dinosaur teeth indicate that Arctic dinosaurs endured cooler climates than their mid-latitude counterparts, perhaps migrating short distances. The new avian fossils suggest that birds, too, formed integral components of these high-latitude food webs.
“Birds likely occupied ecological niches ranging from aerial insectivores to piscivores and small‐game foragers,” said Druckenmiller. “Egg-laying points near riverbanks would have brought them into close proximity with juvenile hadrosaurs grazing on lush vegetation, creating dynamic interspecific interactions.”
Indeed, articulated hadrosaur skeletons recovered nearby show puncture marks and gouges interpreted as theropod predation, but avian traces—such as tiny theropod-like footprints—co-occur, suggesting both birds and small dinosaurs hunted insects or scavenged carcasses. Cretaceous plant communities—comprising magnolias, dawn redwoods, and ginkgo relatives—provided seeds and flowers, sustaining granivorous and nectarivorous birds. Aquatic insects emerging from rivers, as well as fish populations, supplied abundant food for diving and surface-feeding species.
Implications for Avian Evolution and Biogeography
Filling a Major Evolutionary Gap
Prior to this discovery, Alaskan Cretaceous avifauna remained absent from the fossil record, aside from rare trackways. By pushing polar bird nesting back to the Campanian age, the new findings reshape interpretations of avian dispersal and climate tolerance.
“Before this, we believed polar nesting evolved no earlier than the Eocene, when global temperatures spiked. Instead, these birds thrived during cooler, greenhouse‐like conditions stressed by seasonal extremes,” commented Dr. Steve Brusatte, Professor of Paleontology and Evolution at the University of Edinburgh, who was not involved in the study. “It shows that high‐latitude avian ecosystems have been stable, multi‐trophic communities for tens of millions of years, rather than a recent ecological novelty.”
Molecular Clock Correlations
Genomic studies have estimated that many modern bird lineages diverged well before the K–Pg extinction event (66 million years ago). However, fossil calibration points—particularly at high latitudes—were scarce. The Prince Creek fossils provide concrete calibration data for molecular clock analyses. By anchoring the divergence times of neornithine clades to 73 million years ago, researchers can refine phylogenetic estimates of crown‐group birds.
“We can now assert with confidence that certain lineages leading to modern ducks, shorebirds, and perhaps even songbirds existed in the Campanian Arctic,” Wilson said. “This fossil evidence reinforces molecular dates suggesting deep Cretaceous roots for Neornithes.”
Biogeographic Patterns
The presence of Ichthyornithes and Hesperornithes in both mid‐latitude North America (e.g., Kansas, Montana) and the high Arctic indicates broad latitudinal ranges. Migratory behavior likely facilitated gene flow between populations, as summer food surpluses at high latitudes enticed breeders northward, while milder winters at lower latitudes offered survival refugia.
“Polar regions during the Late Cretaceous acted as seasonal breeding grounds for numerous taxa, including birds,” Druckenmiller said. “This pattern foreshadows modern migratory circuits, such as those linking Siberia and Alaska to temperate North America.”
Technological Advances: Tiny Bones, Big Discoveries
The Prince Creek team credits recent methodological improvements for enabling such breakthroughs. Micro‐CT imaging, scanning electron microscopy (SEM), and synchrotron-based X-ray fluorescence (XRF) mapping allowed researchers to characterize minute anatomical features—such as the vascular canals in embryonic limb bones—without destructive sampling.
“Twenty years ago, these microfossils might have gone unnoticed or been dissolved by acid preparation. Today, we can sift submillimeter sediments and digitally reconstruct entire embryonic skeletons in three dimensions,” said Wilson. “Technology has transformed our capacity to detect fragile avian remains hidden within dinosaur‐dominated deposits.”
Looking Forward: Open Questions and Future Research
Despite the excitement, many questions remain unanswered. Among them:
- Seasonal Residence versus Migration: While embryonic remains imply summer breeding, it is unclear whether any species overwintered in the Arctic. Isotopic analyses of bone chemistry (e.g., oxygen and carbon isotopes) could reveal seasonal movements but require well-preserved, unaltered specimens.
- Nesting Behaviors and Site Fidelity: Did Cretaceous birds dig simple ground scrapes like many modern shorebirds, or did they nest in sheltered vegetation? Future discoveries of eggshell fragments with embryonic remains might illuminate clutch sizes, egg morphology, and nesting strategies.
- Climate Resilience and Extinction Survivorship: High-latitude Cretaceous ecosystems endured dynamic climate shifts leading up to the K–Pg mass extinction. Which avian lineages survived the asteroid impact, and did polar populations die out entirely? Comparative studies with lower-latitude avian fossils may clarify extinction selectivity.
To address these queries, the team plans to expand fieldwork along previously inaccessible stretches of the Colville River and collaborate with geochemists for isotopic studies. Additionally, they will screen sediments from adjacent Prince Creek outcrops in the Eagle Shale Formation to search for more complete avian skeletons and eggshell specimens.
Expert Perspectives on Arctic Avifauna Origins
Paleornithologist Dr. Julia Clarke of the University of Texas at Austin praised the Prince Creek findings as “a watershed moment for our understanding of avian adaptation.” She commented, “These discoveries demonstrate that polar bird communities were not an offshoot of Eocene warmth, as once hypothesized. Instead, birds consistently exploited high-latitude advantages—endless twilight insect emergences, plant growth under continuous daylight—for tens of millions of years prior to the end‐Cretaceous extinction.”
Similarly, Dr. Jacques Gauthier of Yale University—an early proponent of cladistic placement of early birds—remarked that “Cretaceous Arctic birds challenge long-held views about climate tolerance thresholds. The convergence of morphological features—such as toothlessness and limb proportions—mirror adaptations seen in modern migratory shorebirds. We may have underestimated the ability of birds to capitalize on polar resource pulses even under greenhouse warming.”
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Conclusions: A New Chapter in Polar Paleontology
The 73‐million‐year‐old bird fossils from Alaska’s Prince Creek Formation rewrite the narrative of avian evolution in polar realms. Not only do they push back the first known instances of polar nesting by over 25 million years, but they also reveal that birds occupied and exploited Arctic ecosystems alongside dinosaurs. Through meticulous excavation, high‐precision imaging, and interdisciplinary collaboration, researchers have unveiled a complex, Cretaceous polar avifauna that included toothed seabirds, diving foot-propelled species, and early ancestors of modern ducks and shorebirds.
As the scientific community digests these revelations, the broader implications resonate: Arctic high‐latitude nesting is not a modern ecological anomaly but a deeply rooted evolutionary strategy. Future work—combining paleontological, geochemical, and molecular approaches—will further delineate how these ancient polar birds fared through climate transitions and mass extinctions. For now, the Prince Creek discoveries stand as a testament to the resilience and ingenuity of early birds, whose descendants continue to grace Arctic skies year after year.
