A bit of a controversy surrounds when to stop feeding hummingbirds coming to your backyard feeder each fall.
Some people say September 1st, while others claim it is all right to leave it hanging until the hummingbirds leave. The argument suggests that the hummingbirds would be encouraged to stay around an artificial food source too long and might not migrate early enough to survive.
I spotted several female Ruby-throated Hummingbirds in Lake Park, Milwaukee recently, looking healthy and capable of migrating whenever they felt like it. They were alternating between loading up on jewelweed nectar for one minute and resting on branches the next. The scene was mostly peaceful with many fall flowers available, but a few nectar squabbles broke out anyway.
The Cornell Lab of Ornithology claims the need to take down feeders early because it discourages a timely migration is a myth. Hummingbirds, like other birds, are more likely to leave naturally because of the shortening hours of daylight, rather than the availability of food.
They seem to know naturally when to leave for their own good and no amount of feeder food will encourage them to stick around when it is time to go. Cornell Lab even recommends you leave your feeder up for a couple of weeks after seeing the last hummingbird to supplement any stragglers that may have timed their departure poorly.
Taking it down or leaving it up, a feeder is largely for our enjoyment anyway. There is a female Ruby-throated Hummingbird hovering six-inches outside my window right now.