If you can wean him off the seeds and get him to eat pellets, that is ideal. You could consider removing food at night, presenting pellets first thing in the morning (when most hungry) and then providing a mix of healthy seeds + pellets for a specified time period during the day. There are birds out there who have and will starve to death rather than eat pellets cold-turkey. Obviously, one day without seeds won't kill your bird, so you could try it (but only if your bird is in good health already). I would be very careful assuming that an addict will just reform. Some do, some don't.
Keep track of your bird's weight if you can and don't give up. Present veggies repeatedly and eat them in front of your bird. It took months for my bird to try anything green..like, 6 + with near daily exposure.
The next thing I say with extreme caution because you can kill your bird with supplements if you overdo fat soluble vitamins such as A and D (to name a few). There are some decent supplements out there if you know
exactly how much to give each day, but these still pose risks for overdose unless you know what you are doing--
especially if it turns out your bird is eating pellets and you just aren't noticing (they are already fortified). My favorite vitamin powder is Nekton-S,
BUT, I seriously hate their directions on the bottle because they are super confusing and you will overdose your bird unless you are a mathematician and can read super-fine print lol---sooo talk to a vet and they will figure out how much you need to give. I know for a fact that my bird just grinds a fine amount of powder from her fortified pellets, so I am okay supplementing.
If you find that your bird isn't eating pellets or veg and you decide to go the supplement route, make sure your vet does an analysis of your bird's weight and vitamin needs and make sure you know that they aren't eating enough pellets to throw off the vitamin balance ----my Umbrella Cockatoo (who weighs more than 1lb) is supposed to get around 1/5 of a gram of Nekton S daily, with is 1/5 of the TINY scoop that comes with the bottle. You would need to be extremely careful to make sure that you didn't overdo it. I am ranting a bit because I found out I had been giving mine too much a few months back, and thank God, she is okay (as is her blood-work). It is a great supplement if you know how much to give, but you will need more information from the vet before proceeding. In the event that you do give it, it mixes easily with moist food (so I give a bit in my bird's daily ration of plain oatmeal---some birds can get super hormonal from wet foods, so that is also something to consider).
Here is a link to the rant I recently posted about this supplement and its terrible instructions.
http://www.parrotforums.com/general...warning-nekton-s-vitaminsupplement-birds.html
