yes it would take a bird.

the best thing to do is get several different size shot in 3" and see which one puts the most pellets in the head and neck of the target.do them all at different yardage.20 , 25 , 30 ; thats about the max. I would try to taske one.with the 20 ga. it loses it's punck after about 30 to 35 yards.

that just my opinion.I took many birds with my 20 ga. mod. choke with 3" #6 shot. I would not shoot past 30 yards.if they didn't get that close, then I wait till another day.
gette'm close take more birds!