"The child loves the birds."
Translation:Το παιδί αγαπά τα πουλιά.
is this not the nominative case?
What exactly do you mean with "this"?
In the sentence Το παιδί αγαπά τα πουλιά, το παιδί is the subject and is therefore in the nominative case; τα πουλιά is the direct object and is therefore in the accusative case.
(As is normal for Indo-European languages, from Greek to Russian and from Sanskrit to English, the accusative and nominative forms are completely identical for neuter words.)