During the Cretaceous-Paleogene extinction event, which marked the end of the age of dinosaurs around 66 million years ago, prehistoric birds were among the few groups to survive. This extinction was triggered by the impact of a massive asteroid—about 10 kilometers in diameter—on what is now the Yucatán Peninsula in Mexico. The collision created the Chicxulub crater and released vast amounts of dust, sulfur, and soot into the atmosphere. This led to a "impact winter," where sunlight was blocked for several years, causing global temperatures to drop to about -10°C and halting plant photosynthesis. A recent study published in the journal Current Biology on September 10, 2026, highlights how certain bird ancestors managed to survive this catastrophic event. The study, led by a team of American paleontologists, biologists, and geologists, examined fossilized feathers found in a coprolite—fossilized dinosaur feces—discovered in Montana in 2016. Using advanced imaging techniques, researchers identified that the coprolite contained not only feathers but also fragments of foot bones. These remains belonged to the hesperornithiformes, a group of flightless, marine birds that resembled modern gulls or grebes. The feathers found showed a low structural index and high barb density—traits seen in modern aquatic birds that help reduce water permeability and improve insulation. The researchers emphasized the importance of insulating plumage for survival during the extreme cold. They noted that the architecture of modern feathers was already present in some bird species before the asteroid impact. However, many early birds had feathers that were not sufficient for the drastic temperature drop. Those that survived possessed highly insulating plumage, which helped maintain body heat. The way these birds molted also played a key role. Birds that shed all their feathers at once became vulnerable, as they were left without insulation and unable to fly. In contrast, the ancestors of modern birds had a sequential molting process, allowing them to shed feathers gradually and maintain both flight and insulation. In addition to physical adaptations, the birds' diet was a crucial factor in their survival. The absence of teeth in the ancestors of modern birds turned out to be an evolutionary advantage. As plants died off and the food chain collapsed, birds with beaks capable of cracking open seeds could access food resources that were still available in the soil. This opportunistic diet allowed these birds to endure the environmental collapse, while other species that relied on a more specialized diet perished. These combined traits—insulating feathers, efficient molting, and a flexible diet—helped certain bird lineages not only survive the mass extinction but also thrive in the new world that emerged afterward.