( ( The ( ability ( to ( respond ( to ( ( reliable ( environmental cues ) ) ( such ( as photoperiod ) ) ) ) ) ) ) ) ( ( ( is ( critical ( for ( migrating birds ) ) ) ) ( because ( they ( can ( ( ( ( ( anticipate ( seasonal changes ) ) ( in environments ) ) and ) then ) ( ( prepare ( for migration ) ) ( by ( storing ( ( energy and ) nutrients ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN ability) (S (VP (TO to) (VP (VB respond) (PP (TO to) (NP (NP (JJ reliable) (JJ environmental) (NNS cues)) (PP (JJ such) (IN as) (NP (NN photoperiod))))))))) (VP (VBZ is) (ADJP (JJ critical) (PP (IN for) (NP (JJ migrating) (NNS birds)))) (SBAR (IN because) (S (NP (PRP they)) (VP (MD can) (VP (VP (VB anticipate) (NP (JJ seasonal) (NNS changes)) (PP (IN in) (NP (NNS environments)))) (CC and) (ADVP (RB then)) (VP (VB prepare) (PP (IN for) (NP (NN migration))) (PP (IN by) (S (VP (VBG storing) (NP (NN energy) (CC and) (NNS nutrients))))))))))) (. .)))
The ability to respond to reliable environmental cues such as photoperiod is critical for migrating birds because they can anticipate seasonal changes in environments and then prepare for migration by storing energy and nutrients.
(ROOT (S (NP (NP (DT A) (NN squirrel)) (VP (VBG storing) (NP (NNS nuts)))) (VP (VBZ is) (VP (VBG preparing) (PP (IN for) (NP (NP (DT a) (JJ seasonal) (NN change)) (PP (IN in) (NP (DT the) (NN environment))))))) (. .)))