I thought a lot about whether should I take and share photos about this, but I decided to do it. Maybe there is a vet (or someone with the same or similar experience) on the Hive blockchain too. I already wrote to a vet on the Facebook Messenger, but he have not seen my message so far. I sent a few photos to him too. I have not posted these photos on Reddit so far, because currently I do not have a Reddit account.
The vet is far away from me, working in a wild bird hospital, but I really hope that someone will be able to take my Harris's hawk to a vet in the next few days. The postwoman offered a car transfer, and she also said that she will asks vets in the nearby. Maybe the bird hospitals will also have volunteers for a car transport, seeing how bad is the current condition of my bird.
My current condition of my bird:
Many of her feathers fallen out (especially on/around her crop), but fortunately/luckily there is no wound on her. He looks very tired almost constantly in the previous few days, but she have good appetite (she eat 15-20 gramm of meat per day), and she is tame, and she jump/fly to my arm.
But something is certainly not right. I currently do not know what can cause this. Multiple people mentioned that probably this is caused by some kind of infection. There was a mouse in the house approximately one week ago. We sat. Probably it was from that mouse. At first we thought about a rat attack, but there is no wound on my Harris's hawk.
I really hope that soon a vet will be able to check her. And I also hope that this is not so bad as it looks.
Either way, yesterday (on 2023.01.25) I talked to 
If I will have any news, then I will write about it.
Have a nice day. All the best. Greetings and much love from Hungary.