I had several packages of bees that I installed last year into Warre hives here in Maryland. I dutifully fed pollen and syrup to get them going. Spring flow was just getting a boom on. For various reasons, some of the hives could not get to the syrup that I provided and did better or as well as the fed hives. All the hives - fed and unfed -are still going strong. So I would join the chorus of those who suggest that you initially feed, but keep it to a minimum and stop as soon as you can. If you can cut a piece of one of the langstroth combs and rubberband it / lash it / wire it to one of the Warre bars, you'll probably encourage a lot of good behavior right off the bat and you can also hold off on the sugar syrup. I made some wire frames for some of my warre bars to that purpose, and they worked well, although the bees didn't like to build past the wire part, so I would just do one of them at most. But you will be amazed at how fast bees can draw comb in the warre. Here's one of my hives (this was an inside observation warre) at just two weeks after package install (and the unfed outside ones were doing even better!):
Eastern seaboard springtime is a beautiful bounty!