It's definitely not too late to start training with him. I would either start with a dummy with a wing attached, or a tennis ball that's been in a bag full of feathers to pick up the scent, and start trying to get him/he excited about playing with these items/toys. From there, start bringing him/her around pigeons/quail that are confined to a cage. Just keep praising the dog and encouraging him/her to investigate the birds at his/her own pace. Once you see that they're comfortable you can let them fly around the dog. Hopefully, the prey drive starts to activate and they become more and more excited about the idea of birds.