You don’t need to have a licence to keep a wild bird that was taken or killed legally, but you do need to be able to prove that you own it legally.
To prove you own it legally, you should keep a record of when and where the bird was found . Photos of road kill site and injuries if apparent etc
You do not need a licence to take it to a taxidermist however should you decide to sell the specimen to either the taxidermist or sell it when it has been mounted then you will need to contact DEFRA/NATURAL ENGLAND in order to obtain an Article 10 Licence....
I think u can take it to the vets too to get some sort of certificate.
Op i take it u know 100% how sparrow was killed? No chance injured elsewhere in a different manner to wot u think?
A while ago was some taxidermy in local paper cheap but no tickets with it, didn't fancy having a load of stuffed BoP's in house with no idea how they were killed.
Broadarrow will be correct above but it does get quite complicted when buying taxidermy esp if it could be over a certain age 1978? i think as i doesn't need a ticket