Learn Italian: Quell'uccello là è nero. - That bird there is black.

The word quello (that) changes its ending depending on the noun that follows it, following the exact same rules as the Italian words for "the". Because uccello is a masculine noun starting with a vowel, you would say l'uccello for "the bird". Therefore, "that bird" drops the final vowel and becomes quell'uccello.

If quell' already means "that", why do we add là in this sentence?

Adding là (there) or lì (there) right after the noun is a common way to emphasize distance in Italian. It is just like saying "that bird over there" in English instead of just "that bird".

Why does là have an accent mark?

The accent mark tells you to stress that vowel when speaking, but more importantly, it tells this written word apart from la. Without the accent, la means "the" (for feminine nouns) or "her". With the accent, là means "there".

Would quell' change if we were talking about a feminine animal?

No, quell' is used for both masculine and feminine singular nouns that start with a vowel, like quell'anatra for "that duck". However, the describing word at the end of the sentence would need to change to match the feminine noun, making it nera instead of nero.