。
Collecting eggs is his job.
Literal
Egg [object-を] gather-up-[nominalizer-の] [subject-が] he [possessive-の] job is.
の here is a nominalizer — it turns the verb phrase 卵を取り集める ('to collect eggs') into a noun phrase 'the collecting of eggs,' which then becomes the subject of the main clause via が. 取り集める is a compound verb: 取る ('take') + 集める ('gather'), with 取り adding a faint 'pick up and' nuance.