The most common and most likely answer to this crossword clue is the 7 letter word GANNETS
I've seen this crossword clue in The Daily Telegraph
G
A
N
N
E
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S
More clues leading to the result GANNETS
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 = gannets.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 GANNETS mean?
GANNETS noun- Any of three species of large seabird in the genus Morus, of the family Sulidae. They have black and white bodies and long pointed wings, and hunt for fish by plunge diving and pursuing their prey underwater.
- A voracious eater; a glutton.