The first year we watched Ruby-throated-hummingbirds (Ruby, Rubies) we got a late start in the season. We noticed that one Ruby would attempt to take over our feeder and drive off all others. Usually this was a Ruby male and usually the male dominated the feeder until late in the season. At this time, a female drove off the Ruby male and then she dominated the feeder.
At this time we thought that all Ruby hummingbirds were so territorial that only one bird would come to our feeder at a time. Watching Youtube videos of dozens of hummingbirds surrounding a feeder made us envious.
And there the issue rested until a year ago. I was visiting a marina in Eastern North Carolina in early June which had a hummingbird feeder. About a half dozen birds surrounded the feeder and more or less shared it with only a little nudging back and forth. I presumed these must be some sort of different hummingbirds as all the rubies I had ever seen would never have allowed this to happen.
A year later in Winston Salem, we set up a feeder much earlier. We had seen an occasional bird as early as late April and we didn’t want to miss the opportunity to feed them on their way north. Although a few would inspect our feeder, during the month of May, none stopped. Then in early June, ruby throated hummingbirds began to arrive and feed at our feeder. At first it was only one, then we noticed that there were at least three different birds feeding at our station. All were females and while none fed at the same time, there was no interference by another in terms of using the feeder. It was a serial sharing relationship. This isn’t much of a relationship, but it is at least friendlier than the hostile behavior we had observed a couple of years before. This lasted for about a month. Not only did they feed at the syrup feeder, they would land in a nearby fruit tree and catch fruit flies.
Then in mid-July, males began arriving and it wasn’t too long until a ruby male began chasing off other rubies as they tried to feed. He chased off males and females alike. It occurred to me, then, that the birds I had witnessed in Eastern North Carolina were indeed female Rubies and the reason for their cooperative feeding was twofold:
it is likely they were just arriving from a long migration from Central America and needed to replenish their fat stores. Hence, as long as the feeder was available most of the time, they weren’t in a position to fight off other birds. The need to eat exceeded the need to dominate the feeder.
Females might be less aggressive and territorial than males (although late in the season in the first year they had demonstrated a willingness and ability to be so).
It is now early August and I expect the male who has ‘captured’ our feeder to continue to dominate it for the month. But I predict a larger female will drive him off late in August or early September. That strategy makes sense. She, after all, needs to build up body weight for the flight back to Central America. What doesn’t make sense is why the male chooses to dominate the feeder against all – including females.
Perhaps some clever person will explain that.