- “Neornithines [modern birds] may have been able to survive the extinction as a result of their abilities to dive, swim, or seek shelter in water and marshlands. Many species of neornithines can build burrows, or nest in tree holes or termite nests, all of which provided shelter from the environmental effects at the K–Pg boundary.”
- - from the Wikipedia article “Cretaceous–Paleogene extinction event”
A little round head covered in matted brown feathers poked up through a hole in the ice, followed by a pair of equally waterlogged gray-white wings. Tiny claws on their leading edges dug into the ice and the bird swiftly levered himself out of the freezing water. Opening his beak to drop the disappointingly small fish he had caught onto his webbed feet, he opened his wings wide, turned his face to the dust-shrouded sky, and shrieked his defiance at the broken world.
The bird had faint, blurry recollections of a time when the lakeshore had thronged with hungry giants and his parents had trained him to keep quiet and stay close to cover. Now he knew that, even standing out here near the middle of the flat frozen expanse, he could make all the noise he wanted and no predators would come after him—there just weren’t any big enough to challenge a bird his size. Many days ago, when internal urges drove him to ignore the ice and prepare for mating season, he had half-considered building a nest right out on the lake, near the spots where the ice most often cracked and the underwater hunting was easiest. But of course no female would agree to such madness—and now, in what passed for late spring, the ice was crisscrossed with the scratched footprints of many other birds and strange furry beasts, most of them small enough to make for a tasty snack if he could catch one, but a few of them possibly big enough to make a snack of one of his chicks.
The fish was small, but not quite small enough to swallow whole. Keeping his wings spread to dry in the chilly afternoon air, but lowering their tips to rest on the ice, the exhausted bird dropped his head to the fish and tore ravenously into it, gulping down most of the flesh in a matter of seconds, then using his foot-claws to scrape out bits of tasty muscle from the crevices between close-set ribs. He shook his wings weakly to help them dry, which stirred long-dormant memories. Was there another use for these shivering limbs? Perhaps he didn’t have to walk all the way back to his burrow?
As quickly as it had surfaced, the strange notion faded into the back of his mind. With a final glance at the murky gray-brown sky, he trudged away from the fish skeleton toward the distant shore.
Suddenly, impossibly, the world brightened. Light glared off the ice, nearly blinding the astonished bird. He looked up again and saw a blue-white rift in the dust clouds, even brighter than the ice—intolerable. Terrified, he stuck his head under his wing to block out the glare.
Was it happening again?
The memory was etched into his mind: one morning, a searing red-white light had streaked across the sky, followed by a trail of smoke and a thunderous roar that faded as the light dropped behind the distant hills, then suddenly grew louder again as a tree-shaped cloud of dust grew above the horizon. The dust had spread over the whole sky, blotting out the—the other bright thing, which the bird had all but forgotten. That was the last he had seen of it, except for one day not long after, when—
But the light faded again, and the memory with it. Cautiously lifting his wing away from his eye, the bird saw with relief that the sky had returned to normal. He resumed his long and weary trek across the ice.
- For several hours following the Chicxulub impact, the entire Earth was bathed with intense infrared radiation from ballistically reentering ejecta. The global heat pulse would have killed unsheltered organisms directly and ignited fires at places where adequate fuel was available. Sheltering underground, within natural cavities, or in water would have been a necessary but not always sufficient condition for survival. . . .
- Being too large to find a hole to hide in would have been a death sentence. . . .
- [S]ome of the same behaviors could have been used to cope with other stresses that followed. For example, burrowing protects from cold as well as from heat.
- - “Survival in the first hours of the Cenozoic,” the journal article cited for the quote above
The bird stepped gingerly over the roots of a dead tree that snaked along the steep streambank and stuck down into the water. The stream’s merry burbling was the sound of home, but he had no desire to step into its frigid water just now. Between the third and fourth roots was the entrance to his burrow and the promise of real warmth.
The burrow was tiny, and if he entered now, his mate wouldn’t have room to edge around him and escape. He screeched a demand, and his mate reluctantly squeezed her way out through the narrow entrance hole. They clacked their beaks together in a brief greeting, and she plodded off in search of more food for herself and their chicks.
He hurriedly crawled inside to take over the role of nest-sitter. The two remaining unhatched eggs were still warm from his mate’s underside. The two healthy chicks climbed onto his back and slipped into the downy feathers between his folded wings. They and the sickly one, which sat squeezed between her father’s flank and the root cleft at the back of the burrow, all chirped at him insistently until he twisted his neck around to vomit a little of the fish into each of their upturned beaks.
When they had quieted, he tucked his beak under his wing and settled in for a long wait. Sometimes it took all day for his mate to find enough food. Other days she came home without enough left in her stomach to feed the chicks. Swimming took so much energy that the bird and his mate often foraged in the dirt for insects or worms instead, but even then it took all their strength to make it through a day.
Sometimes their hunger drove them to extremes. The bird harbored painfully mixed feelings about his sickly chick: a desire to feed her, care for her, and nurture her to health, mixed with a growing impulse to use her as a food source for the rest of the family.
He had a vague sense that life hadn’t always been this hard, and sometimes, for brief moments, that made him sad and angry. For now, though, nestled with his chicks in his cozy burrow, he was warm and content.
- Many warm-blooded, semiaquatic mammals and birds could have survived in lakes, marshes, or swamplands having dense sheltering vegetation unlikely to burn fully. Some of these endotherms may have been capable of remaining underwater [throughout the global heat pulse], surfacing only occasionally to breathe.
- - “Survival in the first hours of the Cenozoic”
Drowsing on his nest, the bird slipped into a nightmare. He was trapped underwater with currents of red-orange flame sweeping overhead. Finally he had to breathe, but somehow knew he could only dip his beak into the searing hot air—the rest of him must remain submerged in the cool of the lake.
After taking a gulp of air and submerging again, he decided to try swimming away from the flames. At first it seemed he was making no progress—no matter how hard he swam, the water surface above still flickered with dancing orange light. Then it finally grew dark, so he popped his head above water—but somehow the air was just as hot as before! He ducked back below the surface and began swimming again.
Swimming became something else. The lake was gone—the world was gone. Now he moved through empty air, and it seemed the most natural thing in the world. He flapped his wings and ascended through the darkness, searching for something, he knew not what.
The darkness above him suddenly feathered away, revealing a bright blue expanse, in the midst of which was a source of warmth and brilliant radiance so bright he couldn’t look at it. He looked down instead, and saw the familiar gray-brown cloud surface that he knew to be the sky—but somehow it was below him now. He had climbed above the sky!
But there was no food up here, and his chicks were waiting. Reluctantly, he folded his wings and dove back into the clouds—and awoke, still sitting on his nest, his chicks chirping again with renewed hunger.
The bird had raised several families of hatchlings by now, and knew that if they survived long enough, these little ones would one day grow up and set out on their own. But, he wondered, would any of them ever have a chance to soar above the sky?