Conservator, Science, Waterfowl

How do ducks know when it’s time to migrate?

The Duck Doctors are in, sharing insights from the wild!

By Ash Melo, M.Sc. October 30, 2026

Every fall, ducks take to the skies on a journey that can span hundreds or even thousands of kilometres.

By Ash Melo, M.Sc.

Ash Melo’s curiosity for migration timing took flight during her undergraduate studies, where she researched the migration of purple martins and dragonflies at Oak Hammock Marsh in Manitoba. Today, that interest has come full circle. Ash now makes her own daily migration to Oak Hammock Marsh, home to Ducks Unlimited Canada’s (DUC) Institute for Wetland and Waterfowl Research — the science division of DUC that guides the work of conservation staff — where she works as a biologist. In her role, she supports research and conservation efforts by exploring how biodiversity responds to landcover changes, including wetland and grassland restoration.

Every fall, ducks take to the skies on a journey that can span hundreds or even thousands of kilometres. Many will return to the same wintering areas year after year, leaving at nearly the same time each season. This consistency might leave you wondering: how do ducks know when it’s time to migrate?

A built-in calendar

The most important signal is one that changes predictably every year: the length of daylight. This is known as the photoperiod, which means the number of daylight hours in a day. As the summer turns to fall, days gradually become shorter. Ducks are highly sensitive to this shift.

The shorter days trigger changes in their bodies and behaviour. Ducks begin eating more, building up fat reserves that will fuel migration, and become more restless as the urge to move increases. A fancy term used to describe this “migratory restlessness” is the German word zugunruhe. Even if temperatures stay warm, the shortening days set the process in motion. Because photoperiod follows the same pattern each year, ducks have a reliable cue to anticipate the change in seasons.

Reading the weather

While day length sets the seasonal timing, weather often influences exactly when birds move. Cold fronts, strong winds and dropping temperatures often act as triggers for migration. A brisk north wind, for example, can help ducks travel more efficiently, allowing them to cover long distances while using less energy. This is why large numbers of ducks are often seen migrating after sudden changes in weather. In contrast, mild conditions can slow things down, allowing ducks to remain farther north for longer.

Migrating ducks over a prairie wetland. © DUC

Following the food

Ducks can also be clued into when it’s time to move south by the availability of food on the landscape. In the fall, they spend much of their time feeding to build the energy reserves they need to power through migration and survive the winter. When wetlands remain productive and food is available, birds may delay their departure. As wetlands freeze, dry out or provide less food, ducks are motivated to move on.

In some years, unusual weather like drought or early freeze-up can shift when and where ducks migrate. This is why networks of healthy wetlands along migration routes are so crucial: they provide the food and habitat ducks rely on no matter the route they take.

Experience plays a role

Not all ducks respond in exactly the same way. Young ducks making their first journey south rely heavily on instinct and environmental cues. Older birds, however, draw on past experience to return to areas where they have previously found good sources of food or places to spend the winter. This combination of instinct and experience helps ducks adjust their movements from year to year.

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Ducks don’t rely on a single signal to decide when to migrate. It’s a combination of internal ‘clock’ and changing conditions on the landscape that influences when they move.

Ash Melo

Because these conditions can vary from year to year, migration timing and routes can look a little different each year.

There’s still much to learn about how ducks respond to changing conditions, and that’s part of what makes studying them so fascinating.

Curious to learn more about ducks and DUC’s science? Check out the Duck Doctors playlist on our YouTube channel and dive into more of the science behind wetlands, wildlife and the species we love.

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