Twittering over the ash
Flying has a great energetic cost, but it can also be a strong advantage to better move in search of food. If you are mostly terrestrial but can potentially fly if necessary, this advantage reaches its maximum. That's how birds were able to survive the K-Pg event and how, most of them, were able to endure the mass extinction of the Lentocene.
Of all antarctic vertebrates, ground tyrants were the less impacted by the END. While large species completely died, at least 4 small semi-fossorial ground tyrants were able to survive. They are at the moment the most abundant terrestrial vertebrates found in Antarctica, being found in all three Green Refuges.
One species, the emissary of the ash (Cinityrannus novum), was the first vertebrate to rapidly re-expand its territory in the fern thickets that now cover most of the continent, feeding on invertebrates and the few herbs that were capable of flourishing under the shade of ferns.
No larger than a thrush, this bird was able to thrive after the END thanks to its fossorial and flying capacity, exploiting any piece of suitable land that remains in Antarctica.
Emissaries of the ash mostly move on the ground and rarely forage on trees due to the loss of the hallux, which allows perching for passerine birds.
Like ancestral tyrants, their nests are excavated in the ground in order to protect chicks from predators and thermal shocks, an unintentionally advantageous behavior that saved this bird from the END. As you can imagine, the trophic chain of Antarctica will start again only thanks to these little passerines.
Along with ground tyrants, another flying bird was able to exploit the barren habitats of Antarctica: the cinderegg (Ovovivipera clastica), the last surviving of the 24 species of eggpouchers of Antarctica.
Of all ovoviviparous cuckoos, cindereggs were the ones with the most generalistic diet and greater distribution, which allowed them to somehow withstand the effects of the END. They are sympatric with the emissaries of the ash but, unlike them, they live at lower densities and give birth to their chicks on the top of small rocks.
They possess long legs and perching feet, which enable them to search for food both on the ground and on trees; aside from insects, snails and seeds, cindereggs have learned to feed on ground tyrants' eggs, because of their abundance.
While being the only eggpoucher remaining in Antarctica, it's not impossible that other species have survived in the rest of the globe and will gradually recolonize the continent again in the future.
