I would not wait to find my bees starving before I fed them!
During the spring you probably do not really need to feed, I quit feeding my new package because they were flying like crazy and making drone comb under the feeder instead of eating the syrup. I will start up again soon, the spring flow is tapering off here, and I need them up to weight before winter. Typically it is necessary to feed during the dearth with new hives here, otherwise they go into winter in bad condition, we don't always get a good fall flow.
As noted above, you should have at least a couple combs of honey and pollen in the hive, and honey above the brood at least in the top brood box if you have two. Less than that, they are short and can actually starve if they don't stop raising brood. We like local queens for that reason, they all shut down brood rearing in August rather than making useless brood and eating all their stores.
This fall, you will need to check to make sure they have enough stores for winter, I'd guess 80 lbs of honey and plenty of pollen (unless you are in the mountains, then I'd guess 100 lbs), but you should check with local beeks to see what they recommend.
My rule of thumb for new hives, either swarms or packages, is to feed unless there is a strong flow on until they are up to winter conditions -- I lost my first hive because I thought the soybean honey the put in a super was enough. Wrong, the bottom deep was completely empty and they ate all that soybean honey before October, and didn't have enough bees to keep the wax moths under control in the spring -- or maybe it was hive beetles, at any rate the lost the queen and dwindled away. Won't make that mistake again....
Peter