Depends
I am refering to mainly small upland birds like quail. I have shot them and had them land God knows where. I would never, ever have found the bird. If it was wounded I couldn't finish it off, Either way, meat would have been wasted.
My dog has found 99.9% of the birds I have shot. I have no idea how she found some of the birds as they landed in brush that was all but impossible to penetrate. Or they landed in high grass that would have made looking for the needle in the haystack a picnic in comparrison.
I suppose on larger birds where finding a cripple should be easy then hunting without a dog, is OK, I suppose. But I do think that hunting the smaller species without a dog is unehtical. I do believe hunting dogs are a great conservaton tool. After all, an ethical hunter will do everything he or she can to retrieve downed game, even if one has to use a dog.