Hello from JustAnswer.
Could you attach a picture of the skin lesions, preferably a lesion that has not been damaged by scratching?
I had asked for a picture and have not heard back.
Diagnosing bird mites is frequently difficult and there is no method that will work in 100% of cases, or even 99% of cases.
It is correct that the method of identification of bird mites would require microscopic examination. However, the best method for collection of the specimen can vary according to the nature of the lesions, which is why I asked for a picture. A scraping may be appropriate, but if there are burrows that contain fluid, expression of that fluid may be more likely to yield a good specimen. In some cases, it would be better to collect multiple specimens by various methods to have a better chance to detect bird mites.
If I can provide any additional information, please let me know.