Picking out penguins

The southern lights - the aurora australis - flicker across the sky during the dark of the Antarctic winter. As the sun returns, so do the Adelie penguins. They come to one of their traditional colonies a mile from Mawson Base. It is now one of best studied of all colonies. A wire fenced corridor has a device that counts and weighs the penguins as they walk by, but a few must still be caught and measured in detail to keep a record of the colony's progress. One is given a prominent marking so it can be identified at a distance. The mark will disappear at the next moult and does not lessen the affections of the bird's partner.