"Two birds were sitting on the roof."
Translation:Dwa ptaki siedziały na dachu.
polish gender works different with plurals. With verbs, adjectives and pronouns we have two "plural genders", masculine personal, and not masculine personal
Masculine personal is : - masculine personal plural nouns - groups that contain at least one masculine person - groups that contain at least one person and at least one masculine animated being (ex a girl and a dog)
not masculine personal is all other: - neuter plural nouns - feminine plural nouns - masculine not personal nouns
Those are two separate things.
Being animate or inanimate only matters for masculine singular nouns in Accusative (Widzę zielony stół = I see a green table, Widzę zielonego ptaka = I see a green bird).
In plural, it matters whether the noun is 'masculine personal' or not. "ptak" is masculine, sure, but it's not a person. Therefore it goes under the second plural, known under the beautiful name of 'not masculine-personal'.