The black-headed gull is not really a black-headed bird, more chocolate-brown - in fact, for much of the year, it has a white head. It is most definitely not a ‘seagull’ and is found commonly almost anywhere inland

https://files.ohai.social/media_attachments/files/111/189/642/948/874/766/original/6d0e255b15596718.jpg 

 @8976b041 I was confused at first when I saw the English name. In my language it's called "River gull"... or less commonly "laugher gull". In fact the first one I saw didn't even have a dark head!