季节性工人向农场迁移在夏季很常见。

The ___migration of seasonal workers to farms is common in summer.

蝴蝶在每年的迁徙期间来到墨西哥。

The butterflies come to Mexico during their annual ___migration.

农村人口向沿海城市迁移的现象持续不断。

There is constant ___migration from rural villages to coastal cities.