> From what I have seen, they prefer to go south for the winter.

Judging from the habits of Apis dorsata, these is true: 

Apis dorsata has a regular annual cycle of migration in Sri Lanka. In February the colonies are spread throughout the coastal plains and the North Central Region. In June and July they migrate to the Up Country, which they leave again in October-November. 

The swarms seem to migrate in several stages, remaining for some days at a resting place between flights. These have different characteristics from the nest sites. Before the swarm flew off, migration dances indicated the direction of its departure. 

These dances occurred all over the cluster, unlike food dances which occurred only on the area where the light intensity was greatest. If the bees could not see the sun or sky, dance and flight activities were very low, but migration dances indicated a constant direction. 

source: Koeniger, N., & Koeniger, G. (1980). Observations and experiments on migration and dance communication of Apsis dorsata in Sri Lanka. Journal of Apicultural Research, 19(1), 21-34.

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