What does Skellig do with the children in the attic, it's special?

In Chapter 31, Skellig sits before the window frame in the attic, his wings opened wide. He doesn't turn, and the children say nothing. An owl flies in and drops something for Skellig. Another owl does the same, and the first does it again. Mina realizes they are feeding him.

Skellig turns to look at them and asks them to come forward. They meet in the middle of the room and Michael can see how strong Skellig now seems. They hold hands and turn about in a dance. Each face goes from dark to light. Michael is overwhelmed and wants to stop, but the other two encourage him to hold on. Michael finally feels the others’ beating hearts, and a smile spreads across his face. It is as if they were one thing, one being. It seems like he has his own wings, and Mina has wings, and they rise up over the old house on Crow Road.