I will include below my recommendations for diet, knowing that this is not a good time for change. However it will help. He may really like the yam bread recipe.
Do not feed the grit. The calcium is not bioavailable, it is often contaminated, and it will cause GI issues. Additional vitamins do nothing. The best thing is a good basic diet with veg--high quality pellets and leafy greens.
You may find that he is good in a smaller, more protected cage. They know when they are vulnerable.
Do not let him fly, as he ,may not have the coordination and could injure himself badly.
Massage of the neck will make him feel better but will not fix the problem. So long as he enjoys it, all OK.
YAM BREAD (cornbread mix+cooked yam)
1' cube per bird
RICE MIX (cooked short-grain brown rice plus fresh veg)
1/4 cup per bird daily
PELLETS (we recommend Harrison's and T.O.P.)
Entire leaves of greens poked through the cage wires or on branches
Cooked yams or squash
Whole carrots, tops included
Half of apple and whole (opened but not peeled) banana poked on sticks (in the aviaries)
Grapes, citrus, pomegranate, persimmon, etc. One small slice per bird. Put on twigs etc.
Here are a few suggestions that I give everyone: important!
The following guidelines help with basic issues such as nutrition, obesity, good immune status. Surprising how the following can make a bird healthy, and how infrequently birds are ill if they are on the following regimen. No amount of medicine is going to work if the birds' basic needs are not met.
great resource links:
Birds should be on a high-quality, preferably prescription, pelleted diet: I prefer High-potency Harrison's
In addition, they should be offered dark leafy greens, cooked sweet potatoes, yams, squash, pumpkin; entire (tops and bottoms) fresh carrots and so forth. No seeds (and that means a mix, or millet, or sprays, etc. etc.) and only healthy, low-fat high fiber people food. A dietary change should be closely monitored and supervised by your avian vet.
Birds should get 12-14 hours dark, quiet, uninterrupted sleep at night. Any less and they can suffer from sleep deprivation and associated illnesses. They should be covered or their cage placed in a dark room that is not used after they go to bed.
The cage material should be cleaned everyday, and twice a day if the bird is really messy. Paper towels, newspaper, bath towels are ok. Never use corn cob, sawdust, wood chips, or walnut shell.
Food and water dishes should be cleaned and changed daily. Keep one set cleaned while the other is in use.
Fresh, perishable food should be placed in separate food bowls. Remove fresh food from the cage after a couple of hours to avoid spoilage.
Change cage papers daily, and clean the grate and tray weekly.
Clean food debris or droppings from toys and perches as needed (which can be as often as once a day).
Grit is not necessary for birds, and will cause digestive problems and death. The best sources of minerals (and vitamins) are leafy greens. Never give grit, gravel sandpaper or cement perches. A bird will eat those to excess when it is not feeling well or if there is a nutritional deficiency. They do not need it at all (an old myth from the poultry days, even poultry do not need it). It can cause an impaction and lead to serious or fatal consequences.