How the shell protected them: how birds survived the extinction of dinosaurs (video).

In the Netflix documentary series "Our Planet," the sixth chapter focuses on birds and their evolutionary success, as other dinosaurs went extinct following the asteroid impact. The program mentions that some birds simply hatched from eggs laid before the catastrophe, which helped them navigate the new world, as reported by IFLScience.

But is this truly the case? Much of the series, according to researchers, brings to life peer-reviewed scientific studies, or at least offers plausible interpretations of the data discovered by scientists. However, scientists challenge the claim that birds survived because they hatched from eggs laid prior to the disaster.

According to Dr. Melanie Durrin from Uppsala University, most birds likely wouldn't have been able to hatch if their parents perished due to the asteroid impact. The fact is that most species require someone to incubate the eggs until the chicks are ready to emerge. However, there are some birds whose eggs do not need constant care, such as those that build nests providing warmth through the decomposition of organic material. Nonetheless, hatching is just part of the issue.

Many birds also hatch in such an underdeveloped state that they cannot move independently. However, there are precocial species—those that have some protection from predators at birth or hatching. Nevertheless, even normal precocial chicks cannot survive entirely on their own. Super-precocial birds, especially those with long legs, can run after prey immediately after birth, and some can even fly on the day they hatch. Yet, they still require some parental care.

Regardless, according to Dr. Durrin, it is unwise to assume that modern bird behavior reflects that of their ancestors who lived on Earth around 66 million years ago. Still, scientists note that from an evolutionary perspective, it would be quite strange if all the birds that survived the mass extinctions were super-precocial, yet almost all their descendants became dependent at birth.

Dr. Durrin also believes there are other gaps in this story. The fact is that eggshells cannot protect against infrared radiation. Researchers believe that the primary issue during this mass extinction was radioactive fallout, making it quite curious how birds managed to survive even if their parents left the eggs in protected areas.

How Did Birds Survive During the Mass Extinction?

According to Dr. Durrin, it is likely that birds survived because they were located in the Southern Hemisphere. Not only were most of them, especially those in Australia, much farther from the impact site and less exposed to the initial blast, but the impact occurred during their autumn. Birds that were hibernating at that time were shielded from the initial explosion and may have awakened when plant recovery had already begun.

Researchers also believe that some surviving bird species may have become trapped on the southern continent, where they were protected. Once vegetation recovered, birds likely faced no issues colonizing the north.

Dr. Derek Larson from the Royal BC Museum states that he and his colleagues compared the beaks of bird-sized dinosaurs from the Late Cretaceous period with those found later. The scientists concluded that some species managed to survive because they were toothless and fed on seeds.

In simple terms, those who managed to avoid being scorched by initial radiation could feed on seeds long enough to sustain life and wait for vegetation to recover. Meanwhile, predators and fruit-eaters faced starvation.