Above (two photos): 2nd win Caspian-type Gull. As there is a hybrid zone of cachinnans-argentatus in central Poland it is probably unwise to assign all Caspian-type gulls to specific identification. This bird looks good and even shows a mirror on p10. However the washed out 'dirty' upperpart markings are not something I generally associate with Caspian Gulls and even though it is quite possible that this is simply variation, I wouldn't know for sure.
This 1st winter Caspian Gull (botton one of the three gull shots) is more typical of what to expect of this species in this particular plumage.
Another one of these dark juvenile Herring Gulls (above). I don't know what is going on there- late birds or northern birds. It looks big- is this a juvenile argentatus?
Also on the farm today, birds of note included four Long-eared Owls still, one Peregrine, 2 Water Pipits on the enclosed beds, 32 Gadwall, 40 Shoveler, 100+ Teal and 10 Pochard. There are about 10-15 Long-tailed tits moving around the site with half a dozen Goldcrest.
It looks like Song Thrushes like the open areas of Fathen. I couldn't find the Stonechats or the Dartford Warbler but I flushed about 10 Song Thrushes from the same area.