Some cockatiels can take more time than others to stop being a baby. But, there could be more to this. He is definitely begging for baby formula. The squealing/crying is classic baby cockatiel begging, as is the head bobbing. And doing this while self-feeding is his way of pacifying himself.
I would first suggest calling the pet shop to find out if they may have still been hand feeding him some. Seven months is a long time for a cockatiel to go unsold, and if they were handfeeding other chicks, they may have given him some just to keep him tame or because he begged. There is absolutely nothing wrong with this, but it would explain his begging. He may not be physically dependent on the formula, but he still wants some.
If they were not hand feeding him, ask them at what age did they wean him? Or had been sold and returned? It’s possible he was forced to wean at a specific age. This unfortunately happens because animal rights activists have pressured many States to make it illegal to sell unweaned chicks. The problem with that is birds are not one size fits all. Some wean quickly, but some need more time. They may go ahead and self-feed out of hunger, but it affects their behavior and causes insecurities and food issues.
In either case, re-weaning can be very helpful. You simply buy some hand feeding formula, and supplement his self-feeding with formula. Find out if they used a syringe or spoon for hand feeding and use the same thing. You can then use the abundance weaning process(you can Google this), which is making a variety of healthy foods available to him, while still hand feeding him in the morning and evening. Each morning, before offering formula, give him his pellets, some chopped veggies and some warm, soft food – this can be cooked brown rice with chopped veggies mixed in. You can even prepare some thick formula and put it in a small cup. Give him these foods, and then leave the room. Make sure he can’t see or hear you for about an hour. Then you can return, and offer to hand feed him. Offer more foods during the day, and then repeat the process in the evening, offering him formula before bedtime. He may still want the formula for a few more weeks, maybe even longer, but he will eventually give it up. And since you mentioned he doesn’t care for pellets, you may want to try him on some of our Nutri-Berries. These are formulated the same as a pellet, but they are not ground up. They provide whole seeds along with other nutritious ingredients and are a nutritionally complete diet. You really should not offer loose seed from a mix. The seeds are not fresh enough to retain their nutrients, and if vitamins have been added, they are lost when the bird removes the hull. The seeds in Nutri-Berries are already hulled, so the added nutrients are consumed. The best way to introduce Nutri-Berries is to crumble them, so they look like loose seeds. You can mix them with the seeds you are feeding already, and then gradually reduce the loose seeds until he is only eating Nutri-Berries.
And lastly, you might want to take him to an Avian Vet for a check up, especially if the shop was not still hand feeding him. He could have a mild infection which is making him feel hungry all the time. This is fairly common with hand fed birds and it’s best to catch it and get it treated before he gets sick.
Please let us know how it goes – hopefully you can get him properly weaned and content.
Thank you for asking Lafeber,