( ( ( Severe ( limb loss ) ) ( to ( four limbs ) ) ) . )
(ROOT (S (VP (VB Severe) (NP (NN limb) (NN loss)) (PP (TO to) (NP (CD four) (NNS limbs)))) (. .)))
Severe limb loss to four limbs.
(ROOT (S (NP (NNP Birds)) (VP (VBP have) (NP (CD four) (NNS limbs))) (. .)))