Galochka/галочка also means a check mark, so better be avoided
I think there are only two bird-ish endearments in Russian that are more or less common:
птичка - means a birdy
ласточка - means a swallow
Both are pretty intimate and not every girl would like it
if you wanna go with baby raven then use воронёнок
if you wanna go with baby jackdow then use галчёнок
if you wanna go with baby sparrow then use воробушек
I'm not sure it's gonna pass as endearment but it's original for sureIf you wanna be hell lot more original go with феникс/phoenix (just joking)
Avoid сорока/magpie and ворона/crow and any diminutives of these