Here are just a few things I've learned about weaning:
1) If there's a stressful event, hand-feed more for a couple of days. I had to take Kizzy on a long trip when I had urgent eye surgery. That day and the following day, she had three hand-feedings to sustain her. By the following day, she was eating well on her own again.
2) Eating is a social thing for birds. Whatever Kizzy eats, I eat, too. Sometimes she won't try it right away, but if she sees me eat it, she will try it at some point. In the mornings, I usually have to get her started this way. I ran out of Harrison's and I don't much like the taste of Lafeber's and Zupreem, so I will eat veggies in front of her if she doesn't get going on her own. XD
3) In the morning especially, hand the baby bits of crumbled pellets and veggies. In the wild, their parents would be stuffing their beaks with edibles.
4) If eating in front of them doesn't work and handing them bits of food doesn't work, you will have to jumpstart Yoshi by hand-feeding him a small amount of formula. Hand-feeding is more than just nourishment. You are assuring the bird that he is still part of the flock and that you love him. Without those bonds, he will resort to begging until he feels secure again. Unfortunately, a baby bird can starve to death due to regression.
5) I don't like percentages. If someone tells you it's OK if the bird loses X% amount of weight, there are some "what ifs." What if my baby is naturally petite and got really, really fat during the weeks of hand-feeding? She could lose more than what is considered "OK" and still be fine. What if my baby was already on the skinny side? If he loses too large a percentage he could be in trouble. What if I'm allowing my baby to fly and the percentages are skewed to represent the weight of a clipped bird?
If you think Yoshi is too thin, I would go back to three feedings a day until his little belly is rounded and then start over. If they've eaten on their own before, usually it isn't too hard to get things rolling again.
I have always "eyeballed" the weight of weaning chicks. Yes, they should be a little on the thin side, but the keel should never stick out, nor should the breast be in a V shape. There should be enough muscle on either side of the keel to make the breast rounded. Every day, I look carefully at Kizzy's breast. If I think she's getting a bit too thin, I hand-feed again. If I think she isn't eating enough food on her own, I hand-feed.
Instead of a schedule, it's more like a give-and-take dance. It's pretty difficult to put a weaning bird on a schedule. Some of my greys took much longer to wean than what the books said, but I didn't cut corners because weaning is a difficult time for any bird and it needs to be done very carefully.
Now I have to wake up my flying toddler and see if she will continue to eat on her own or if I must jumpstart her today.
Cheers.
