They winter over in the Caribbean, Central America and South America.

它们在加勒比海、中美洲和南美洲过冬。

The one that migrates from eastern United States and Canada in the summertime to Mexico in the winter, over the last 10 years we calculated that that subpopulation has declined between 20 and 72 percent.

它们夏天从美国东部和加拿大迁徙到冬天的墨西哥，在过去的10年里，我们计算出这一亚群数量下降了20%到72%。