Bird Shot at home defense distances is a game stopper. No handgun would even come close with the exception of a CNS hit.
Based on my experience dispatching various animals at close range there was no reason to believe that bird shot would not have a similar effect on humans. That theory was supported by a buddy of mine who is the chief radiologist at the largest level 1 trauma center in the southeast US. The number of gunshot injuries they see each year is unreal. In over 30 years he has never seen a single individual that has survived a shotgun blast to the torso at room distances. I asked him if it matter what type of load was used and he said no. He said at room distances the shot acted as a single frangible projectile and the trauma and blood loss was "not survivable"
On the other hand, they patch folks up regularly with multiple shots to the torso from all flavors of handgun rounds. Some of these have been on the receiving end of local law enforcement shooting .40 and .45 ACP glocks fed with Remington bonded Golden sabers, Winchester Ranger T, Speer gold dots etc.
I keep #4 turkey loads in mine, but I have no reason to doubt the opinion of my friend especially since it mirrors what most of the EMT, trauma center type folks have related in this thread.