You might get nauseous or even pass out if you try to give yourself exposure therapy. Eat comforting food whatever comfortable you can afford. You can try to do it yourself, but having the help of someone else will certainly be better. If you can't afford a therapist, try to find a friend, child or relative to talk to you about birds cheerfully. You can mentor a child as a teaching mentor and as payment listen to the child's innocent perspective of birds. (That's not a good idea, I'm just brainstorming. It would only really be appropriate of you had a niece, nephew or offspring.)
If those four things about birds disgust you I'm afraid there's really nothing your going to find good about birds. Lol.
If there was something about a bird that you could appreciate, like their part of the ecosystem, they eat bugs when bugs get too frequent, they build nests and are stereotypical perfect parents. They push the babies out of the nest to teach them how to fly, (the classic throw the baby in deep water approach.) Maybe colorful birds. If you have a favorite color, you can look at pictures of birds in your favorite color, like red Cardinals or blue blue Jay's. If you have a favorite location on earth you can look at what types of birds are there. Here in western washington we have the blue body black headed stellar Jay. In Ecuador they have the macaw. Etc.
You might find something at all appreciatable about a bird, and just think of that when you look at a bird.
If you have a fan, turn on the fan while you read about them. To make sure you don't stop breathing. When I was in highschool I was shown a video on brain surgery and I stopped breathing and collapsed in front of the whole class.
You can definitely appreciate flight about a bird. You can think of the wright brothers imitating the bird soar. You can appreciate nocturnal owls for looking less birdhead like. They look more human than other birds. You can think of the bald eagle or golden eagle as symbols or national championship in America and Europe. You can think of Turkey as the pilgrim forefathers main source of protein. You can think of a tasty drumstick as an American picnic staple. (Do you eat turkey and chicken?) Turkey has a lot of tryptophan which is the precursor to serotonin, which is the chemical that makes everyone happy. You can think of a turkey as being a very happy animal.
Something you might not like about birds and their heads is that they are very stupid and not masculine. You might be offended by a man who resembles a bird. Know that in China every twelve years is Rooster year, where they actually believe the children born that year have personalities that resemble birds.
If dirtiness is the main problem just think about how dirty things are in general. It is not healthy in my opinion to accept dirtiness, but it is a common function of life that things get "dirty" or rather uncontrollably disorganized as I like to put it. You might prefer the simplicity of a tree to the complexity of a bird. You might have a very neat apartment. I don't blame you by being offended by dirt.
Sickliness is something that all birds naturally put out. Birds are sick to human standards. If a human were to be transformed into a bird he would feel excruciatingly sick. Maybe think of sickness as relative. Something that is sick to a Muslim is good to a Christian and viceversa. Think of sickness as a foreign language that needs to be translated.
I'm sure you can get over birds if that is actually what you want to do.
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