When do Orioles Migrate South?

I haven’t seen my orioles since the end of July. Where did they go? Isn’t it too early to migrate south? Should I take my oriole feeder down?

Dream Weavers

Image by ben_long_hair via FlickrBaltimore Orioles arrive at their mid-Michigan breeding grounds near the end of April. Soon after the female alone begins to build a nest. This consists of weaving and tying thousands of stitches and knots with her beak into a woven hanging-basket.

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It can take as many as 15 days for her to weave a nest and the result is an engineering masterpiece of plant fiber, grasses, vine and tree bark. Orioles build the nest on small branches 6 to 45 feet in the air, to keep them safe from predators. Female orioles are also in charge when it's time to incubate the eggs and brood the young in the nest. Then both parents feed the young which fledge about 30 days from egg laying.

Orioles make only one nesting attempt per year. So depending on the success of the birds in finding mates and a nesting site, they may be done raising a new family anytime from mid-June to mid-August. That means they’re free to move around after that. Some may start down south and some adult orioles are just secretive at the end of July when they begin their fall molt and may not visit feeders.

Usually, there are a few early individuals that start migration. These are followed south by a much larger volume of migrants. Finally the peak tapers off gradually to a few lingering stragglers. Most of the bird books will tell you that they leave Michigan by mid-September but there is no set schedule and I'd leave your feeder up a little while longer, just in case.

Related article: Migration of Birds: When Birds Migrate http://www.npwrc.usgs.gov/resource/birds/migratio/when.htm