The most common and most likely answer to this crossword clue is the 8 letter word ROOSTERS
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More clues leading to the result ROOSTERS
Buddy explains!

The straight part
We know that "Birds" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case birds = roosters.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ROOSTERS mean?
ROOSTERS noun- A male domestic chicken (Gallus gallus domesticus) or other gallinaceous bird.
- A bird or bat which roosts or is roosting.
- An informer.
- A violent or disorderly person.
- A powerful, prideful, or pompous person.
- (originally United States slang) A man.
- A wild violet, when used in a children's game based on cockfighting.
- Legislation solely devised to benefit the legislators proposing it.