Many of these clues have multiple possible answers, but it quickly becomes obvious that there is an answer for each which is or sounds like a single letter.
BEE (B)
AYE (I)
ARR (R)
DEE (D) – Dexter’s sister is named Dee Dee
V
EH (A)
R
EYE (I)
e – As in eCommerce, eReader, etc.
Tea (T)
WHY (Y) – Who, What, Where, When, and Why
Reading these letters in order down the pages gives BIRD VARIETY, which is a clue for the thematic answer JAY.