I finally caught the rufuos hummingbird that's been terrorizing the feeders All the other Anna's let him drive them off from one feeder and promptly move to the other...until the rufous get wind and flies off to drive them back to the original one
the number varies depending on the time of year and how dry things are...we're part of the migration path but we have some that stay year round...right now since my garden and feeders are the only thing with flowers/nectar around (summer is very dry in California - we won't get rain until late October - nothing is blooming outside of people's gardens) I'd hazard a guess that there are several dozen if not more! Early morning and just before sunset both 10-seater feeders are full with others waiting...
The anna's seem to be relatively cooperative...the males do fight among each other but seem to be more willing to let everyone drink without tooooo much fuss. What I've noticed is the crowd will be working one feeder, the rufous comes and yells and beats them all up until he's got the feeder to himself not realizing that the crowd has all gone over to the other feeder!! Eventually he sees them all at the second feeder and comes zooming over to start the battle again with the annas all heading back to the original feeder