Unless you are where they want to be you will have a real hard time bringing in those big flocks. You can counter this by putting out a huge spread, flagging, and making lots of noise but it still may not work for the bigger groups. Early in the season you may have more success with this because of the uneducated juveniles.
Your best bet would probably be to watch where they go and set up there.
Good Luck!
Your best bet would probably be to watch where they go and set up there.
Good Luck!