my lab did not become real good until he was around 3 yrs old,now at 4 ,he is getting even better.
1 to 2,he was not very good.

i think your dog just needs more time in field around birds.

hide a bird as often as you can if you cant get around birds.
i got mine real good at grouse by driving around before seaon on old dirt roads.
we would see a birds,i would back up, get out and let dog loose saying,BIRD..
after about 3 times of doing that, he knows now what is.