Those of you who have been following my Flickr photostream or have been following this blog will probably know that I have a favorite gull: an adult European Herring Gull which has been color-ringed 27 years ago as a fledgling in the dunes of Wassenaar nearby The Hague, The Netherlands.
Because of it’s age and the amount of times I have seen him (75 times sofar since I first observed him in 2009), I’ve come to bond with this gull.
Most of my observations are done during the breeding season (although we have no proof that he is actively breeding), during which he regularly visits my local fishing market in Leiden. He usually first appears in April or so and can be seen until the end of September.
He then sort of disappears off the radar and we have no real knowledge of exactly where he spends the winter, although he is sometimes seen in the seaside resort of Katwijk aan Zee nearby Leiden.
This was also true this year: my last observation here in Leiden was on September 29. On my subsequent visits to the market on the following 2 Saturdays he did not show up, very much as expected.
Re-sighting in Katwijk aan Zee
Yesterday I got an e-mail from Kees Camphuysen (who currently manages this ringing project), with the subject “White triangle” and only containing the following question: “Are you thinking what I am thinking?”.
Curiously I opened the 2 attached photos and tried to find out what this reference to a “white triangle” was about.
Both photos were made by Luuk Punt. The first photo showed an adult Herring Gull standing on the beach in a group of gulls and the 2nd photo was a crop of the same image. The photos were clearly digiscoped from a long distance.
I was expecting to see some kind of odd plumage characteristic but couldn’t see anything out of the ordinary until I noticed a green color ring with a white character on the right leg.
Luuk kindly gave me permission to post his photos here:
Surely this was “my” gull “ZDGA” (ZDGA is an abbreviation for “Zwart D, Groen A” which is Dutch for “Black D, Green A”).
(Incidentally, ZDGA lost his black ring sometime between May 26 and June 2 of this year.)
It was reported though as a gull wearing a green ring with a white triangle, which is fully understandable because of the distance at which the observation was done and the fact that the central part of the “A” has worn off.
This was quite unlucky because out of the 3 letters A on the ring this one is the most difficult to read (but I know from personal experience that the process of reading rings is full of these unlucky moments…).
The other unlucky part of this observation is that the gull cannot immediately be individually identified because of a missing color ring on the left leg.
Looking for an ID
Not knowing which individual he had photographed, Luuk asked for help on a Dutch forum where it was quickly suspected that this was ZDGA. He then sent an e-mail to Kees Camphuysen who in turn asked me for confirmation.
Identifying gulls with missing color rings can be tricky and sometimes impossible because there are usually other individuals which have been ringed as part of the same project and which carry the same ring on the same leg.
In this case though, the puzzle was easily solved. We know that this is ZDGA because of the following characteristics:
- Location. Katwijk aan Zee is only some 10 km from Leiden and ZDGA has been seen there on previous occasions (although mostly in the 1980’s and 1990’s).
- Primary moult. One of the aspects that we are studying in this gull is the stage of the primary moult. On my last observation, P1 to P6 were fully grown, P7 was almost fully grown, P8 had been dropped, and P9 and P10 were still old. Luuk’s photos seem to show a fully grown P7, a gap where P8 should be and an old P9 and P10 (note the small and worn white tips).
- Head streaking. During winter, ZDGA carries extensive winter streaking. The head streaking in Luuk’s photos is very similar.
- Ring wear. The wear on the green ring corresponds to the wear documented for this ring.
The final green ring that’s around
I was then wondering how many individuals of this project had a green ring with the letter A fitted on the right leg, and how many of them are still around.
After checking with Kees, it turns out that 52 individuals had such a ring fitted but that ZDGA is the only one who has been recently seen. Number 2 is White Y Green A which was last seen in 2004 and it’s therefore unlikely that this individual is still around.
Let’s hope that ZDGA is seen many times during this coming winter. I’ll be expecting him back in Leiden next January.