There area a number of long term scientific projects in the Antarctic, one of them being an annual survey of penguin numbers and breeding success at specific breeding areas. These pictures (taken 5 minutes apart) show such a survey of an Adelie penguin colony on Signy Island in the South Orkneys group.
As they look rather similar it's not easy to know which penguins you've counted and which you haven't. So the answer is to use very dilute paint and tie a brush to the end of a stick, giving each counted penguin a splodge as you count them. The problem on this day was that the rather wet snow that fell meant that the paint mark that was supposed to wash off the next time the penguin went swimming, lasted only a few minutes instead. It didn't make it any easier that the penguins kept laying down and hiding their paint marks as they tried to shield themselves from the worst of the snow.
Photo copyright - Paul Ward / coolantarctica.com