Just got back to Warsaw after a three day/two night trip to Bialowieza Forest:
Birds:
81) Snow Bunting
82) Horned Lark
83) White-backed Woodpecker (and with that lifer, I have seen all 10 Polish woodpecker species)
84) Grey-headed Woodpecker
85) Common Crossbill
86) Northern Goshawk
87) Whooper Swan
88) Yellowhammer
89) Three-toed Woodpecker
90) Tawny Owl
91) Great Grey Shrike
Heard only: Eurasian Pygmy Owl
Also worth noting is that the most common/conspicuous bird around the Bialowieza town were Waxwings which was really nice.
Mammals:
6) Red Fox
7) Red Deer
8) Pine Marten
9) Wild Boar
10) European Hare
11) Bank Vole
12) European Beaver
13) European Bison (better view than my previous visit in 2014)
14) Raccoon Dog
15) Yellow-necked Mouse
16) Fallow Deer
Also quite a few mammal prints, which, given the thick layer of snow everywhere and a new layer falling during the night, were really interesting to look at. Prints less than a day old (based on recent snow fall) include wolf, badger, and mink.
Much more successful on the mammal front than I was expecting, quite a lot of hours spotlighting paid off. The bird list is comparatively lower, but given the time of year it's not bad at all (though I missed Hazel Grouse and Spotted Nutcracker which are two species that I tried to find).