Early season the plumage is lighter and woodies and teal are smaller birds, hence the lighter loads, since the lighter shot size equates to more pellets and the range is often closer we can use a more open choke and still have good pattern density. Late season means thicker plumage and divers can be tough, hence the slightly heavier loads, since the ranges are often longer and due to the larger shot (fewer pellets), we often use tighter chokes as well. However if I could only choose one load for ducks it would be a fast 3" 1 1/8 oz load of #3's... and for geese a heavier 3" 1 1/4 oz load of BB'S. Winchester, Federal, Kent or other is your choice.