The second migration occurred around 200 years before the time of the series.

Migration is usually at night, but may occur during the day, especially when over water.

Particularly interesting is the fact that the migration occurred so recently, about 50,000-70,000 years ago.

The major Islamic migration has occurred in the last 20 years.

The next major migration of blacks occurred between 1813 and 1815.

Migration also occurred at the turn of the twentieth century.

The migration typically occurs at night, usually as individuals or in small groups.

This migration occurred mainly during the years of 1940 to 1970.

Indian migration to other countries has occurred for several centuries.

This enormous migration has occurred largely during the last 20 years.