thank you for this report and the photo's. From what I can see of the code, in combination with the (new) type of metal ring this can only be NZ5. This bird has been seen earlier at a well known Dutch roosting site for Sandwich Terns, north from the original ringing site.
W-NZ5 (NLA NL....1478), 28 June 2013, pullus, de Scheelhoekeilanden, near Stellendam, Zuid-Holland, the Netherlands (51.48.46 N / 04.04.20 E), CR placed
W-NZ5, 24 July 2013, de Putten, Camperduin, Noord-Holland, the Netherlands (52.44.08 N / 04.38.45 E), colour-ring read by Sytze Algera
W-NZ5, 15 August 2013, de Putten, Camperduin, Noord-Holland, the Netherlands (52.44.08 N / 04.38.45 E), colour-ring read by Sytze Algera
W-NZ5, 10 September 2013, Huttoft, Lincolnshire, England ( 53.16.28 N / 00.9.08 E), colour-ring read by Graham Catley
In 2013 we have managed to place nearly 400 colour-rings on Sandwich Terns, 28 of those on breeding adults. We have used a three-digit code always starting with an "N". The N can be followed by two numbers (N50), two letters (NHN), one letter and one number (as with your bird NZ5) or a number and a letter (N4A). In most cases the colour-ring has been placed on the right tarsus and the metal (NLA) ring on the left tarsus. In some cases these positions have been reversed, for example when a bird already wore a metal ring.
These Sandwich Terns have been ringed in two colonies in the southwest of the Netherlands by a joint research group composed of the Research Institute for Nature and Forest/INBO, Bureau Waardenburg and the Ringgroep Delta. Through these colour-ringed birds we hope to gain a better understanding of habitat use, dispersion of juveniles and adults, age of first breeding and recruitment to the various colonies in the southwest of the Netherlands and beyond.
This year there have already been sightings of "our" birds from the North of the Netherlands, Belgium, England, Scotland, Denmark and France.
Thank you again, also on behalf of the other members of the Tern-Team (included in cc).
all the best,