As the poster above said, Vasari colony frigates do it, instead of needing a dedicated ship like the other races.  This is very handy for we Vasari players, as you'll have a couple colony ships roaming around in the early game, they become obsolete once you have a couple Space Eggs (because unlike the other races, Vasari don't use colony frigates to capture neutral extractors), and in the late game they're quick to produce as needed.  Have six or seven of them safely parked at a back-line system with a phase stabilizer, and it becomes really easy to get them where you need them.

Note that since each is consumed when you start construction on the starbase, you'll need to constantly replace your supply of them.  It's handy to have one system that ONLY produces Migrators for starbase use; I generally use my home system for this, as I'll still have one frigate factory there, and I still make capships at my home, but all of my real frigate/cruiser production will be done at a dedicated desert-planet ship factory (5 frigate factories).