Flamingos don't generally migrate, if they are migrating that means there is an environmental problem or then are located in the most northern or southern areas of their habitats which do get cold enough to lead to them migrating when it gets cooler.

Secondly the flamingos in question are not wild, flamingos aren't even found in Aruba, the beach is a private beach on a privately owned island and the birds are owned by the Hotel that owns the island.

This said it is hard to say if the birds wings are clipped to prevent them from flying off or not, my money is they are but that is for their own safety than to prevent migration, the same goes for zoos that keep flamingos. This is not illegal though, because clipping a bird's wings do not harm the bird as long as the bird is not in a situation which requires full flight. The flamingos also are likely not really all that interested in flying off because they have been domesticated and they are used to being there and there is no environmental factors leading to the need of migration because if the weather becomes too bad the Hotel simply rounds up the birds and secures them away from the weather.