Since 1998 we effectively use in our population study the plastic wing tags installed on adult breeding birds. The individual code combines color, shape, left/right position, sex and left/right ring position. For complete identification we need to identify all five attributes:
1) colors used: white – yellow – orange – red – light blue – blue – green – gray (8 variants, always uniform color about 3 ccm)
2) shapes used: rectangle, triangle, roundlet, rhomboid, cogged triangle, rectangle with anterior or posterior appendix, rectangle with elongated edges (8 variants)
3) left or right wing (2 variants)
4) male or female (2 variants)
5) aluminum ring on left/right leg (2 variants)
This gives 512 individual combinations. Combinations of dead birds are reused. Only about 5 birds have lost their tag. More birds have lost their rings! We have birds wearing tags for up to 11 years without problems. We found that the most important part for shape identification is its lower edge. All selected shapes can be identified even from below. Bleaching affects mainly the red color. There is slow degradation towards the next color in the line red – orange – yellow – white.