And another: "They don't keep out of the ground for a long time. You can keep them for a few weeks, but they need to be in cold storage for any longer term, and I doubt whether one can get away with a year of cold storage. Just leave them where they are and figure out what to do next spring (2011) when you will know what is going on around your yard after all this work. You can always buy new bulbs if you need to. Tulips are a bigger problem, as they don't persist very well here in mid-Missouri."
I think what this is saying is I should just leave them as long as feasible. I'll mark which ones I want to move, and then try to keep an eye on things and see what's in danger of being ripped up by contractor machines; if they're not, I'll probably just leave them till fall, when I can overwinter them in the garage.
You’re right to leave them in the ground as long as possible, but many bulbs should be replanted in the fall. As I remember, your renovation will be done in early fall. Tulips, iris, crocuses and daffodils should be (re)planted in the fall. Daylilies, tiger lilies and lilies of the valley are (re)planted in the spring.
Dahlias and some other bulbs will live longer and do better if you dig them up in the fall, but they need to be kept in your cool basement, not garage, as the whole reason you dig them up is to keep them from freezing. The spring bulbs don’t mind being frozen, even in Illinois.
When we’re organized, what we do is take a picture of the garden while blooming, to remember what we might want to move. If you have a bunch of commingled plants, then you’ll need to mark them so you remember which ones are which (now were these the red tulips or the yellow tulips?)
IF you have any perennials, they can be moved in mid-autumn to an interim location and be heeled in (ie move them with a bunch of dirt and let the bundle of newly moved dirt be slightly higher than the rest of the ground). This will tell you where you need to dig up next spring, without hurting the roots/bulbs any more than need be. You might need to mulch heeled-in plants for the winter.
Buy a heavy duty gardening fork for moving big bunches of bulbs or perennials. It’s much better than a shovel.
http://www.acehardware.com/family/index.jsp?categoryId=1260256