Hi again Matko: here's a link to all the rules for Birdforum
As you will find, the pictures are yours and the copyright remains with you for whatever pictures you upload here. If you want to add a watermark or a copyright logo it is up to you. I would suggest however, that you don't make them so noticeable as to detract from the subject.
I hope this helps and we'll soon be able to see some of your images in the Gallery too.