Do birds migrate only to escape the cold?

Cold itself rarely kills a healthy bird with insulating feathers. The real driver is food: insects disappear, water bodies freeze over, and seed or fruit supplies run out, so birds move to where food stays available rather than to literally escape low temperatures.

How do migrating birds know which way to go?

Research points to a combination of cues rather than one sense: the position of the sun and stars, the Earth's magnetic field (detected via a light-sensitive protein in the eye), and learned landmarks such as coastlines and river valleys, with young birds on some routes relying more heavily on an inherited compass direction and older birds correcting with experience.

Bird Atlas

Bird Migration

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Bird migration is the regular, seasonal movement of birds between breeding and non-breeding ranges — driven by food availability and daylight, not simply cold weather.

What migration is

Migration is the regular, predictable movement of a bird population between two or more regions at set times of year — typically a breeding range used in spring and summer and a separate non-breeding range used in autumn and winter. It is distinct from the random dispersal of young birds looking for territory, and from the irregular movements of nomadic species that shift range in response to unpredictable food supplies rather than the calendar.

The trigger for migration is primarily food availability, not temperature directly. Insect-eating species such as the barn swallow and common swift leave Russia and Europe in autumn because flying insects become scarce, not because a swallow's plumage cannot handle cold. Shortening day length acts as the main internal trigger, since it reliably predicts the change in seasons weeks before food actually runs out, giving birds time to build fat reserves and begin the journey.

How migrating birds navigate

Migrating birds use several overlapping cues rather than a single sense. Many species can detect the Earth's magnetic field through a light-sensitive protein in the retina, effectively giving them an internal compass. They also read the position of the sun by day and the rotation of the stars by night, and — especially on well-traveled routes — recognize physical landmarks such as coastlines, mountain ranges, and river valleys.

Distances vary enormously by species. A common kestrel breeding in central Russia may move only a few hundred kilometers to milder wintering grounds, while an Arctic tern travels between polar regions, covering tens of thousands of kilometers a year — among the longest migrations of any animal. Both extremes rely on the same underlying navigation toolkit, timed by the same seasonal cues.