During the "nuclear winter" that followed the fall of a giant meteorite that almost no sunlight reached the Earth's surface, causing the amount of plant biomass sharply decreased and herbivorous dinosaurs began to die out. They were followed by predatory lizards. However, in the soil, there was enough seeds to feed a bird with a toothless beak.

This idea came to mind of the paleontologists who have studied the teeth of maniraptora is a vast treasure of dinosaurs, including the ancestors of modern birds. Most of the members of the group, including the toothed birds went extinct in the late Cretaceous period.

Scientists have suggested that the reason for the survival of birds in their diet. They reconstructed the face of these creatures, they were all from birds with short and strong beaks, suitable for cracking and splitting seeds. Probably survived as well and some birds, specializing in insects.

In 2014, scientists have suggested that birds survived the killing of their relatives global catastrophe due to the shape of their eggs. Bird eggs of the Mesozoic era elongated in form, and are much more symmetry than modern. In addition, shell has considerable porosity.

In the same year, paleontologists explained the evolutionary success of birds is the fact that their ancestors-the dinosaurs — the only branch of dinosaurs, representatives of which over 50 million years continuously decreased in size. Becoming dwarfs in the country of giants, the ancestors of birds to occupy the new ecological niches and learned to climb trees, to plan and fly. As a result, these evolutionary innovations helped the birds survive the deadly lizards to large disasters.