( Needs ( ( motion ( to ( stay aloft ) ) ) . ) )
(ROOT (S (NP (NNS Needs)) (VP (VBZ motion) (S (VP (TO to) (VP (VB stay) (ADVP (RB aloft)))))) (. .)))
Needs motion to stay aloft.
(ROOT (S (NP (NNP Birds)) (VP (VBP need) (NP (DT a) (JJ light-weight) (NN body)) (PP (IN for)) (S (VP (TO to) (VP (VB stay) (ADVP (RB aloft)))))) (. .)))