Presently he hauled the rope back up. The ground crew had tied on three carrying sacks and he carefully put a chick in each and lowered them down. On the ground the chicks were examined, weighed and measured. Each chick had two rings fitted, one to each leg. One was made of metal with a unique number and a reporting address stamped on it, the other ring was a big coloured plastic ring with a unique combination of letters and numbers on it. The first would allow anyone finding the bird to report it, the second, with its big clear figures would allow the scientists to read it using a telescope, without ever having to catch the bird to find out which one it was. The team leader had fitted BEL's ring all those years ago. The chicks were weighed and measured to gauge their age, sex and health. 
The job was over in twenty minutes and the chicks were back in the nest, normality returned.

The bright plastic rings allow individual Ospreys to be identified without ever having to go near the bird. Now scientists can identify pairs, family relationships, returning birds, and birds on migration. Some life histories can have hundreds of sightings over many years.