The Arctic tern commutes between the Arctic and Antarctica, chasing summer all year. About how many kilometres does one bird fly in a single year?

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Answer

About 70,000 km

A tern can live for around 30 years, so its lifetime mileage adds up to about three return trips to the Moon.

How to estimate it

Pole to pole along Earth's surface is half the circumference: 40,000 / 2 = 20,000 km. The tern makes the trip twice a year, so a straight round trip is 40,000 km. Seabirds do not fly straight; they follow winds and coastlines in big S-shaped loops, which adds perhaps 75 percent: 40,000 × 1.75 = 70,000 km. Tracking tags show about 70,000 km per year.

Source: Egevang et al. 2010, PNAS

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