I find how my two-year old classifies birds to be amusing: 1) He called all birds ducks for the longest time, presumably based on being exposed to a bath duck,

I find how my two-year old classifies birds to be amusing: 1) He called all birds ducks for the longest time, presumably based on being exposed to a bath duck, and this weird Youtube video about ducks swimming in the water. 2) Then he called some of them bird, based on being exposed to a bath toy bird. 3) Then he split them up a bit more... parrot, chicken, rooster, etc. He started seeing them in books and real life. 4) At no point could he explain the difference. Still can't. 5) And he definitely thinks the only difference between a rooster and a chicken is colorful feathers. 6) And he's not quite sure about ducks and geese, but usually gets it right.