During the winter we have to keep 5 feeders up and stocked. I have a system of footie socks that slip over to slow the freeze during the cold of sub-freezing days. At night they all have to come in when the temps dip below freezing. In the morning they're hovering over my shoulder scolding if I haven't gotten them out early enough. I suspect they are so territorial as a way to keep warm.
Some of the literature says that the hummingbirds may survive in the wild off of tree pitch. But we live in the 21st century being taken over by crows and starlings- gotta give the little guys a break.