Just because it had a bird on the shell doesn't mean it was birdshot. Federal used to have a bird on the case headstamp of their shotshells, including their full power slug and buckshot loads. Some of the hardest recoiling rounds we were ever issued was the brief period we were issued Federal 0 Buck, 12 (32 cal.) pellet shells and they had a bird on the headstamp. I don't remember why we had them, rather than the usual 9 pellet 00 Buck (which also had the bird), but we probably either got a deal on them or someone ordered the wrong item.