At first I read it and thought of the edible swiftlet nests they turn into soup in other parts of Asia. Then I realised it just means ‘mind the birds, not the menu’. I love how even safety signs can sound delicious here.

Yes, it's a warning sign that there's a bird's nest above and to watch out for droppings from overhead. I agree—the wording is amusing when you first think of edible bird's nests!