You always see tagged birds once in a while. The bigger ones sometimes have tags around the neck but it is more usual to see ringing on the feet, at least on smaller birds. Tagging gives information about the migration of birds between countries. It can also give indictions  of how old wild birds can get .

This Greylag Goose was tagged in Dell of Killyhuntly, near Kinguusie, Highland Region, Scotland on May 22, 2012. Here it is in a meadow just south of Selfoss, South Iceland on April 20, 2015. This is a female Greylag and it was two years old when it was tagged.

It most likely goes to Scotland every year but its breeding place in Iceland is not known.