( Migration ( ( is ( ( an ( adaptive response ) ) ( to ( ( the ( ( ( seasonal or ) geographic ) variation ) ) ( of ( resources ( -LRB- ( ( Gauthreaux 1982 ) -RRB- ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Migration)) (VP (VBZ is) (NP (NP (DT an) (JJ adaptive) (NN response)) (PP (TO to) (NP (NP (DT the) (ADJP (JJ seasonal) (CC or) (JJ geographic)) (NN variation)) (PP (IN of) (NP (NP (NNS resources)) (PRN (-LRB- -LRB-) (NP (NNP Gauthreaux) (CD 1982)) (-RRB- -RRB-)))))))) (. .)))
Migration is an adaptive response to the seasonal or geographic variation of resources (Gauthreaux 1982).
(ROOT (S (NP (NNP Migration)) (VP (VBZ is) (NP (NP (DT an) (NN evolved)) (, ,) (VP (VBN adapted) (NP (NN response)) (PP (TO to) (NP (NP (NN resource) (NN availability)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (NP (NP (DT the) (JJ long-range) (JJ seasonal) (NN movement)) (PP (IN of) (NP (NNS animals)))))))))))) (. .)))