、、。
Two or three of them got pushed out of the nest, and on top of that, they fell off the balcony.
Literal
Those [genitive-の] inside [genitive-の] 2-or-3 birds [subject-が] nest [from-から] be-pushed-out, furthermore balcony [from-も] fall-ended-up.
A sad narrative about baby birds. そのうちの二、三羽 ('of those, two or three') uses 羽 (わ) as the counter for birds — one of the specialized counters Japanese uses to distinguish what's being counted. 押し出される ('be pushed out') is the passive of the compound verb 押し出す (押す 'push' + 出す 'out'). ~てしまう ('end up doing,' 'unfortunately do') attached to 落ちる marks the fall as an unwanted outcome, carrying an implicit 'unfortunately.' さらに~も ('and on top of that, even X also') escalates the misfortune: not only pushed out, but then also fell off the balcony.