Cabelas Trophy Bucks

there are 6 birds that you will find throughout the campaign. most of them will be the actual mission, but a couple are hidden in bushes. here are the birds you need and on what level they first appear.

harlequin duck 6
pintail duck 17
canadian goose 33
blue winged teal 50
snow goose 71
mallard duck 81 (bushes to left of the deer)

Unlocked for me once I shot my first bird in Minnesota on career play... I used a shotgun. Minnesota seems to be one of the latest levels on the game so perhaps you have to pass all of the fowl hunts.