Fred Visscher
 ·  14 June 2018  18:01

Zoals ieder jaar deel ik hier weer even de info die ik over de kolonie heb ontvangen. 

The ringing scheme for Gull-billed Terns is in the process of transformation. This year might be the last one for us to use 4 little colour rings. There has been a meeting in spring and we are waiting for decisions and input from the ringing administration in Wilhelmshaven about which ringing scheme might be the best for the future (most likely including coded rings).

Hence, this year will be kind of like the years before. It is planned to use black rings on the bottom of the left foot indicating the year of birth, together with a contrasting colour-ring starting in order with yellow, white and red. This means you will probably see the first/oldest chicks with yellow over black on the left and 16 colour combinations on the right put together from the colours red, white, green and yellow.

Until today things are going pretty normal in the colony. After an initial delay the colony is now settled (in 2 locations, but within visibility range) and 37 pairs are breeding (same as last year). The maximum number of individual birds observed was 81. The amount of eggs combined is about 20 more than last year, probably due to less predation after laying and an age-effect among the breeding birds (more experienced breeders than last year). Effects of food availability cannot be excluded, but seem unlikely or small compared to other factors. As of today there is still breeding, no hatching going on yet. Thus ringing will likely not start before early July.

Last year we managed to identify over 30 ringed adult individuals which means that up to 50% of the population consists of birds may be born during the runtime of the project. We believe this indicates success of the project as well as reason for and reasonability of the ringing scheme.