Tom Roster did a study on pheasants (and also ducks) leathality with steel. He determined that, for roosters, the appropriate steel was size no. 2. I have used #4 steel and it was inadequate at 30 yards. #2 shot was preferred for ducks as well. The point was, what killed the birds dead most often...
In other experience I have killed smaller geese and cranes with #3, #2, BB, and T steel. The #3 was relatively poor at any distance, breaking wings but not penetrating body cavity on a straight incoming shot. I choose BB's most often.
Have fun!
