( So ( , ( ( ( each acre ) ( in ( Central America ) ) ) ( ( must ( ( hold ( ( six ( or ( seven times ) ) ) ( as ( many birds ) ) ) ) ( as ( ( an acre ) ( of ( their ( breeding grounds ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB So)) (, ,) (NP (NP (DT each) (NN acre)) (PP (IN in) (NP (NNP Central) (NNP America)))) (VP (MD must) (VP (VB hold) (NP (NP (CD six) (CC or) (CD seven) (NNS times)) (PP (IN as) (NP (JJ many) (NNS birds)))) (PP (IN as) (NP (NP (DT an) (NN acre)) (PP (IN of) (NP (PRP$ their) (VBG breeding) (NNS grounds))))))) (. .)))
So, each acre in Central America must hold six or seven times as many birds as an acre of their breeding grounds.
(ROOT (S (NP (NNP Birds)) (VP (VBP live) (CC and) (VBP breed) (PP (IN on) (NP (NP (CD seven)) (PP (IN of) (NP (DT the) (NN continents)))))) (. .)))
Birds live and breed on seven of the continents.