I didn't realize that there are two kinds of gulls... you learn something new every day!!In search for more information I found that there are 2 kind of Gull breeds;
https://dier-en-natuur.infonu.nl/di...nger-meeuw-en-oost-friese-meeuw.html#karakter
Important (translated with google):
The Groninger gull and the East Frisian gull are two breeds of fowl that are very similar to each other. In fact, the similarities are so great that in fact only the eye color, tail range and weight differ between the two breeds. Descriptions are provided for both breeds throughout this article. Where there are differences, this will be discussed per topic in a separate sub-heading.
ps. This info is about the large breed.