It's the work of Hollie, AKA Folk Horror Magpie, who sells intricately taxidermied works on Etsy. Hollie writes that they adhere to "ethical taxidermy", using only dead specimens rather than killing them for the purpose.
Flat is starting to look like a rodent graveyard so I'm hoping to find some homes for these.
I'll be adding to the shop over the coming weeks, maybe some prints and other bits of art.
— Folk Horror Magpie (@folkhorrormagpi) July 10, 2020