if ya where the birds wanna be ya wont need large numbers .... altho later in the season its nuthin for me to set out 60-100 duck decoys if there are large flocks and alot of migrators comin into the area ..... also if the competition gets stiff .... the numbers will help draw those birds in ..... ya wanna be able to pull those birds ..... all i can say is get out there and do it ... ya will learn oer time what ya need where and why .... good luck