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The Binocular Advisor

How Do Hummingbirds
Know when to Migrate?

When should I take down my hummingbird feeders? I still have three ruby-throated hummingbirds here every day. I love seeing them, but I don't want to tempt them to stay longer than they should. -- Sidney P., Fairfield, Iowa

Ruby-throated Hummingbird femaleI'm happy to tell you that you can leave your hummingbird feeders up as long as hummingbirds are visiting them. And then a week or so longer, just in case a straggler comes through.

You need not be afraid of causing the birds to delay their migration and get caught by winter. That isn't going to happen.

It's not the lack of food that tells a hummingbird when to go south. It's the bird's internal biological calendar, or circannual rhythms.

As the time of migration approaches, the hummingbird starts to pack on fat, which will fuel its journey. And then it gets an overwhelming urge to migrate. The biological rhythms run automatically, but they are synchronized and fine tuned by the changing day length.

The amount of food in the environment does not affect the migratory urge. In fact, the birds leave their summer home while food is still plentiful. That way, they are reasonably assured of finding more food along the way.

Ruby-throated HummingbirdSo your hummingbird feeder is not going to tempt the hummers to overstay their schedule. In fact, the sugar water you offer will help the hummingbirds "gas up" for their journey. Hummingbirds that are already on their way south can stop by and replenish their stores, too.

In the western United States, the Anna's hummingbird stays in much of its range year around. But most hummingbirds do go south for the winter. You might as well enjoy their visits on their way.

I always keep my feeders up for a few weeks after I stop seeing hummingbirds in the fall. I continue to change the syrup every couple of jays, to keep the feeder clean and free from mold and fermentation.

Sometimes a late hummingbird straggles by long after all the others have gone. This might be a young bird that hatched late in the season and that wasn't ready to migrate when the others left. I'm glad to be able to offer a little extra help.

4-second QuickTime hummingbird movie

Recipe for hummingbird's Nectar

Hummingbird feeders


— Copyright 2007 Diane Porter

Images copyright 2005-2007 Michael and Diane Porter

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A pretty feeder for hummingbirds

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