Citation:
The phrase 'a flock of birds are' illustrates a common grammatical dilemma regarding subject-verb agreement, especially when a collective noun is involved. Here, 'flock' is a collective noun that refers to a group of birds, and the verb should typically agree with the singular form when the group is viewed as a single unit, leading to 'a flock of birds is.' This situation often creates confusion, particularly in informal speech and writing.