I know my birds can tell the difference between me and my BIL who feeds and waters them. Several roosters have learned to attack him because he recoils in fear (6 ft dude scared of a small rooster, smh). I stick my bare hand in the Ayam ketawa pen and have never been attacked, but he moves back when I open the door, lol. Even if that little guy jumped on my hand and tried to remove a finger, I would just laugh at him, he is pretty much bantam size.
They also rush me when I carry a bucket (because there is probably corn in there) and move away from him when he carries a bucket. They might even be able to distinguish between colors of buckets, but I haven't tested that.
Birds learn quickly when they need to, but when they are not making food or danger decisions, they don't seem very bright and can never see the big picture like (most) humans can.
I would say some poultry are smarter than a chihuahua, but not all poultry. All poultry are far below the IQ of a German Shepard or Collie.