I only had a 2 or 3 birds at my last place and a couple of feeders. My plan was to add feeders and when I got a dozen of so birds, I would put all of them up but a couple or so. I thought I might have to put up maybe 10 feeders. Well, things didn't work out so well for me; I ended up with 20 feeders and 70 plus birds. I have a picture that I took lying on my back of 2 feeders with 21 birds. Two hovering and 19 sitting. Could have got more.

Adding feeders works for some and not for others. But if you add say several feeders you must keep the nectar changed clean and fresh every 2 or 3 days especially during migration in august. I have increased my plant volume and it slowed down my feeder use a good bit which is ok , before that I was hanging 12-15 feeders now only 3 or4. I save on sugar. Add a couple a cheap feeders this summer and see how it works.

If I had lots of flowers up close where I could see the hummers, I would go that route. I only put the feeders up to watch the birds. If a feeder is in the sun or it is a bowl type with the entire surface exposed to the elements thru the feeding holes, then it might have to be changed every 2-3 days. A hummer will not drink soured sugar water, they will however go to someone elses feeder. Bottle feeders do not expose more than the diameter of each hole to the elements. I expected to get drunk on some nectar that I had left while on a 2 week vacation, but I took a big gulp and it was very sweet just like fresh made. While I might change my feeders on a weekly basis, it's hard to tell someone else that because I don't know if the feeders are in the sun or if they were very clean when filled, etc. I try to have enough out for the birds to last 5-7 days. If the nectar gets bad, the birds will leave; they will not stick around. Now this has only happened to me on a vacation or two when it did turn sour or maybe when I was sick.