Dorthy:
According to info the males are not monogamous. They mate with as many females as they can.
I found this site (Much more info than the previous site I posted) that is loaded with tons of info on hummingbirds from migration, to breeding, to USA laws. Anything you ever wanted to know. They have a list of sites that sell feeders(hundreds of them to choose from), vases, shower curtains, you name it. At the top of the site are "tabs" you click on to get to each catagory.
http://www.worldofhummingbirds.com/index.php