IJmuiden Project - Fred Cottaar, José Verbeek, Maarten van Kleinwee & Mars Muusse

(last update: January 01, 2023)

Herring Gull (argenteus) Y.CAX 4CY, May - November 2016, IJmuiden & Katwijk, the Netherlands. Picture: Maarten van Kleinwee & Mars Muusse.

Ringed as breeding 4CY in season 2016 at Forteiland, IJmuiden. Ringed by Fred Cottaar ringing team.

below: Herring Gull (argenteus) Y.CAX 4CY, November 16 2016, Katwijk, the Netherlands. Picture: Mars Muusse.

Some black on the bill.

below: Herring Gull (argenteus) Y.CAX 4CY, August 05 2016, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

Note bill pattern! A dramatic change.

This gull was caught as a breeding male in the gull colony of IJmuiden Forteiland, the Netherlands in May 2016 and ringed as Green Y.CAX.
In May, the bill showed sub-adult features with much black in the lower and upper mandible, a dark yellow base and a pale tip, typical for a Herring Gull of this age.
In August (so after the breeding season), the bill looked very mature with only a small remnant of black on the bill.
In October (and photographed in November), the bill has turned very immature with a pale pink base, a distinct black band across the bill and a yellow tip.

below: Herring Gull (argenteus) Y.CAX 4CY, May 20 2016, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

Clearly sub-adult when trapped at the nest and ringed.

below: Herring Gull (argenteus) Y.CAX 4CY, July 04 2016, Forteiland, the Netherlands. Picture: Maarten van Kleinwee.

below: Herring Gull (argenteus) Y.CAX 4CY, May 20 2016, Forteiland, the Netherlands. Picture: Maarten van Kleinwee.