This is not how real birds fly. Enkidu did this to incessantly attack amidst their powerful flight, perhaps imitating the flying phantasmal beasts of their time.
To counter that, the boy spread his own “wings” further and gathered the vestiges of mana in the skies above the planet.
The boy caught a random glimpse of a giant something swimming in the sky but was too busy to identify what it was.
Enkidu, pushing his body further up, opened their mouth.
“I knew you were a threat to my Master.”
Their words expressed concern but still had a soothing tone to them.
As proof, Enkidu’s next words were spoken with a tranquil smile.
“But I’m glad you were born. If no one else will celebrate your birth, I will.”
“...? Oh... Thanks...”
The boy thanked before thinking, flustered by the unexpected words.
His words and expression showed confusion, but he never left his battle stance.
The same goes for Enkidu. With their body overflowing with magical energy, they took a look at the land expanding below them and spoke with heartfelt relief.
“It’s proof that our planet still hasn’t given up hope.”
After trading remarkably powerful blows, the two opened up the distance between each other as they kept flying higher.

Fate/Strange Fake, Volume 7; Chapter 21 (Beings Shaped In Man's Image)