We still might not know the air-speed velocity of an unladen swallow, but now we know the daily flight distance (up to 500km!) of the tiny arctic tern. Reported in the BBC.
Starting in August and September, the small (3.5oz) bird will head from Greenland and fly to the Weddell Sea, on the shores of Antarctica. It will spend about four or five months in the deep south before heading back to the far north, arriving home in May or June.
A team from Greenland, Denmark, the US, the UK and Iceland attached small (0.05oz) geolocating archival light loggers to the birds' legs to find out exactly where they went on this polar round trip. The devices do not rely on satellite navigation, but record light intensity. This gives an estimate of the local day length, and the times of sunrise and sunset; and from this information it is possible to work out a geographical position of the birds. They banded 50 birds in July 2007 in Greenland, and one year later collected the devices from 10 birds (more birds with loggers were seen in the colony, but these could not be recaptured). More on these cool devices here. More info on these amazing birds here.