there have been some tests, which involved teaching mynah's the color and shape words --circles in red, white and green
squares in blue, purple and orange, and triangles in yellow, pink and brown. (or similar shapes/color combo's)

then they added new colors, and shapes and asked the birds to find all the triagles.. and they birds found the blue and red triangles.. and then asking for all the yellow toys, and the bird seperated out the yellow circles, squares and triangles... (which seems to indicate that birds could identify both colors and shapes, and assigned terms for them- they seemed to understand that yellow was independent of triangle, even if they had learned yellow as "yellow triangle")

but no mynah has ever come up with new words for things..

apes, the learned "fruit" (and specific fruits) and juice (as well as soda, water, and tea..) one ape when first given watermelon, called it a "juicefruit"-- showing it understood the concept of fruit, juice and how these concepts could be used to name something new. Humans do this all the time, (telephone, photograph--etc. we have lots of compound words to express new things that take their names from two seperate ideas/words.)

mynahs only mimic what they have heard. so while they can understand some abstract concepts,)( like "quiet" said in the right tone stops the dog barking) they couldn't form compound words, or concepts them for themselves. Myhans don't answer the questions they hear, they only repeat them.

but this research was on Nova (or some similar science show) more than a few years ago-- and by the time it gets to TV, its old news... I don't know if there is any new research on bird and language.