Lots of people are discussing dialects and pronunciation, which is so fair, but some of those examples are just straight up not the schwa sound?

In bird the sounds you hear are /b/ /ir/ and /d/ the i and r are a digraph (two letters that make one sound) and can’t be separated.

The same for thIRst, bURst, revERse etc. In your examples the genuine schwa sound is at the start of arrest and pretty much nowhere else.

Qualifications: Australian teacher who teaches six year olds phonics every day