Combination of a metal ring (on right leg) and a c-ring (on left leg).
During 2015 c-ring on right tarsus)
note 1 : the colour of the c-ring is changed every year.
* yellow in 2013.
* red in 2014 (some 150 nestlings).
* violet in 2015 (on right tarsus).
* white in 2016 (on right tarsus).