Margen
The Arctic tern breeds during the northern summer and, when the cold sets in, heads for Antarctica to catch the southern one. That way it strings together the planet's two summers and sees more daylight than any other living thing.
It doesn't fly in a straight line: it rides winds and currents, tracing a huge S across the oceans. Tracking studies with geolocators have measured round trips of around 70,000 kilometres a year, with some birds topping 90,000.
Since it can live thirty years, the lifetime total comes to over two million kilometres: the equivalent of going to the Moon and back three times. A bird of barely a hundred grams that spends its whole life, almost by accident, running from winter.