Do hummingbirds come back to the same feeders and or nectar sources every year?
I had found an article awhile back which will answer this question and almost any other you may have. Your question is answered in the first section under 'homones kick in". This is the most in depth and informative article I have ever found. You may or may not know Russ Thompson who roams the hummingbird forums and has his own gallery of copyrighted photos. Anyway even he was impressed with this article that I had found he saved to his favs. Its one of those reads you have to set aside a lot of time as it has several different sections. Enjoy.
Here is a link that might be useful: hummingbird info