a flock of wild ducks的用法和样例：
- A flock of wild ducks inhabits the reeds, and they quack to each other.It seems they are not going to leave and live through the impending winter.
- A flock of wild geese flew overhead.
- Several months went by and sure enough Wally looked up and spotted the flock of wild ducks in formation heading north.
- A flock of wild geese landed by the lake for a short stay.