Ford's heart was still racing from the presence of the beasts that had loomed over the pair. He'd held Mia in place, terrified that she would get some wild idea about running away into her head, and he would lose track of her.
When the birds had finally left, he kept them invisible, fearing the avians' return, and helped Mia to her feet. With just the two of them, his magic could last much longer. Not quite indefinite, but long enough for them to walk safely back to the rest of the group, certainly.
He started to turn to do just that when Mia swayed.
Alarmed, he pulled her against him and evaluated what to do next. His initial impulse was to turn them visible so he could check her for injuries, ask her if she was all right!
The birds had come very close several times; perhaps he'd missed a moment where a talon or beak had slipped past his guard and hurt her. Or maybe in pushing her to the ground he'd caused her to twist her ankle or hit a sharp rock!