The most common and most likely answer to this crossword clue is the 10 letter word KITTIWAKES
I've seen this crossword clue in The Times
K
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More clues leading to the result KITTIWAKES
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 = kittiwakes.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 KITTIWAKES mean?
KITTIWAKES noun- Either of two small gulls in the genus Rissa of the family Laridae that nest in colonies on sea cliffs and spend the winter on the open ocean.