A Migration Shaped by Wind and Food
Arctic terns do not simply draw a straight line between their breeding grounds in the Arctic and their wintering areas near Antarctica. Their route bends across oceans, tracking conditions that make long flights possible: useful winds, productive feeding grounds, and places to rest. A shorter path on a map can be a worse journey if it offers less food or forces birds to fly against prevailing winds.
Riding the Seasonal Food Supply
The birds feed mainly on small fish and other marine prey. As seasons shift, so do the regions where that food is available. By traveling north for the Arctic summer and south for the Antarctic summer, terns can feed and breed during the warmer, brighter part of the year in each hemisphere. Their migration is therefore tied not only to temperature but to the seasonal pulse of life in the ocean.
Long Days, Repeated Twice
Because the Arctic and Antarctic summers occur at opposite times of year, the terns can follow summer from one end of the planet to the other. That gives them unusually long exposure to daylight across the annual cycle, though the route still involves demanding stretches over open water. Wind and food help determine how those stretches fit together.
The result is a journey whose logic is not “take the shortest route,” but reach feeding and breeding conditions that keep recurring with the bright season. The terns’ path is a moving itinerary through the ocean, adjusted to where the next meal and favorable flight conditions are likely to be.
