Over the last 12 to 18 months the dunes and sandy beaches at various points along the Dutch coast line have been reinforced by depositing large amounts of sand.
In the months of January and February 2015, such sand suppletion activities took place at the beach of Scheveningen, the Hague and as ever, the rich sea food that was brought along with the sand attracted large numbers of gulls, many of which were ringed.
The large number of gulls also brought together a group of gull enthousiasts who — in a unique effort — decided to share their observations to get an insight into the number and origin of the ringed gulls that were observed during these activities.
This article summarizes those observations.
The sand suppletion activities at Scheveningen took place from 19 January until 28 February 2015.
First of all, some totals:
|Number of observers that participated||12|
In alphabetical order: August Šimurina-van Rijn, Cornelis Fokker, Gerard Visser, Gerjon Gelling, Johan van ‘t Bosch, Laurens van der Wind, Leo Snellink, Maarten van Kleinwee, Rinse van der Vliet, Rob Hoeben, en Vincent van der Spek.
The following types of gull were observed (ringed and un-ringed):
|Herring Gull||Very high numbers|
|Black-headed Gull||Very high numbers|
|Common Gull||High numbers|
|Great Black-backed Gull||Low numbers|
|Caspian Gull||Low numbers|
|Yellow-legged Gull||Low numbers|
|Scandinavian Herring Gull||Low numbers|
|Lesser Black-backed Gull||Very low numbers|
|Iceland Gull||2 individuals|
|Glaucous Gull||1 indidvidual|
|Mediterranean Gull||1 indidvidual|
On some days, a few thousand Black-headed Gulls were present.
|Number of ringed gulls observed||330|
|Great Black-backed Gull||22|
|Lesser Black-backed Gull *||3|
|Presumed hybrid Herring Gull x Caspian Gull||1|
* Lesser Black-backed Gulls breed in the Netherlands but migrate to southern Europe and Africa during the winter. Especially at the end of the sand suppletion activities, the first individuals just started to return.
The 330 individuals were split over the following countries in which they were ringed:
Even though the observers had the impression that most of the gulls present were sub-adults, the split across the ringed individuals is almost 50-50 and in favour of the adults.
(Port of Rotterdam, Moerdijk,
|Roland-Jan Buijs||Herring Gulls
Lesser Black-backed Gulls
|Various (but mostly The Hague)||Frank Majoor||Black-headed Gulls||52|
|Texel||Kees Camphuysen||Herring Gulls||20|
|IJmuiden||Kees Camphuysen||Herring Gulls||5|
|Rotterdam / The Hague||Norman van Swelm||Herring Gulls||3|
Observing ringed gulls over a set period of time at a set location is a great way to get a sense of the dynamics of that group. We were not surprised to see some individual gulls on a regular basis (sometimes daily) while other individuals were seen only once. Some gulls were also seen in other parts of the region while the activities still took place.
Even though the sand suppletion activities seem to present an almost guaranteed source of food, competition among gulls is high and it also takes skill to pick out small bits of food from a fast flowing band of water.
In contrast, some ringed gulls were expected but not seen, especially Black-headed Gulls. These are ringed at locations close to Scheveningen (Zoetermeer and Leiden), but much fewer of those were seen than was expected. Apparently the attraction of a sand supplietion was not enough to lure them away from their regular wintering locations.
What also surprised us where the low number of second-calendar year Black-headed Gulls.
All in all, the types of species and the numbers in which they appeared is very typical of what can be seen along the Dutch coast at that time of year whenever there is an abundance of food on the beach, whether it is deposited by high winds or artifically such as by sand suppletion activities.
Thank you to all observers
It has been a very interesting excercise to share all observations with a group of dedicated gull enthousiasts and ring readers. Hopefully this will stimulate us to repeat this process at future events to get a better insight at what takes place during such activites.
For now, many thanks to everyone involved!