Once in 2007 and between 2012 and 2018 Gull-billed Tern chicks were tagged with 4 colour-rings (no inscription).
Used colours were:
- Green, Red, Yellow, White (all years)
- Blue, Orange (only 2007, 2012, 2013)
- Black (only 2018, left leg bottom ring only)
The bottom ring on the left leg indicates the year of birth. All other colour combinations were randomly chosen. Reading order of colour rings is bottom of left leg to top of right leg, using English abbreviations.
Colour combination (YWGR) from 2015. (Foto: Martin Gottschling)
Colour combination (GWRW) from 2014. (Foto: Fred Visscher)